International Journal of Biological Macromolecules 43 (2008) 401–414 Contents lists available at ScienceDirect International Journal of Biological Macromolecules journa l homepage: www.e lsev ier .com/ locate / i jb iomac Review Chitosa and en N.M. Alv a 3B’s Research on Tissue Engin b IBB-Institute a r t i c l Article history: Received 12 Au Received in re Accepted 8 Sep Available onlin Keywords: Chitosan Chitosan deriv Biomedical ap Biomaterials Polysaccharides Contents 1. Introd 2. Graft 2.1. 2.2. 2.3. 2.4. 3. Specia 3.1. 3.2. 3.3. 4. “Smar 4.1. 4.2. 5. Applic 5.1. 5.2. 5.3. 5.4. 5.5. 6. Concl Refere ∗ Correspon European Insti Guimarães, Po E-mail add 0141-8130/$ – doi:10.1016/j.i uction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402 copolymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402 Grafting initiated by free radicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402 Grafting using radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403 Enzymatic grafting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404 Cationic graft polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 l cases of chitin and chitosan modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 Phosphorylated chitin and chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 Combination of chitosan derivatives with cyclodextrins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406 Thiol-containing chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 t chitosan”: example of new chitosan-based hydrogels exhibiting temperature-responsive behaviour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408 Graft copolymerized hydrogels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408 Chemically crosslinked blends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410 ations for modified chitosan materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410 Drug delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410 Tissue engineering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 Antimicrobial agents and other biomedical applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 Adsorption of metal ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 Dye removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 usions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 nces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 ding author at: 3B’s Research Group - Biomaterials, Biodegradables and Biomimetics, Dept. of Polymer Engineering, University of Minho, Headquarters of the tute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark, Zona Industrial da Gandra, S. Cláudio do Barco, 4806-909 Caldas das Taipas, rtugal. ress:
[email protected] (N.M. Alves). see front matter © 2008 Elsevier B.V. All rights reserved. jbiomac.2008.09.007 n derivatives obtained by chemical modifications for biomedical vironmental applications esa,b,∗, J.F. Manoa,b Group - Biomaterials, Biodegradables and Biomimetics, Dept. of Polymer Engineering, University of Minho, Headquarters of the European Institute of Excellence eering and Regenerative Medicine, AvePark, Zona Industrial da Gandra, S. Cláudio do Barco, 4806-909 Caldas das Taipas, Guimarães, Portugal for Biotechnology and Bioengineering, Braga, Portugal e i n f o gust 2008 vised form 5 September 2008 tember 2008 e 16 September 2008 atives plications a b s t r a c t Chitosan is a natural based polymer, obtained by alkaline deacetylation of chitin, which presents excel- lent biological properties such as biodegradability and immunological, antibacterial and wound-healing activity. Recently, there has been a growing interest in the chemical modification of chitosan in order to improve its solubility and widen its applications. The main chemical modifications of chitosan that have been proposed in the literature are reviewed in this paper. Moreover, these chemical modifications lead to a wide range of derivatives with a broad range of applications. Recent and relevant examples of the distinct applications, with particular emphasis on tissue engineering, drug delivery and environmental applications, are presented. © 2008 Elsevier B.V. All rights reserved. 402 N.M. Alves, J.F. Mano / International Journal of Biological Macromolecules 43 (2008) 401–414 1. Introduction Chitosan is typically obtained by deacetylation of chitin under alkaline co materials, b annually by exoskeleton insects. It is certain fung composedo � (1–4) glyc degree of d ered thatwh on the origi along the ch and in thes the biodegr icant decrea fully deacet observed [1 Chitosan ibility, biod non-toxic, n fore, chitos biomedicin flocculation solutions, w Recently ification of application groups to t groups [10,1 neutral and ter. Substitu polymers w methods of used.Grafti tives by cov backbone. C grafted. Firs ondly, the h or deacetyl primary de obtain muc idant prope to improve complexati ing adsorpt modifies its ing charact [20,21] and The mai ify chitosan examples o used will be such modifi discussed. 2. Graft co As said b tomodify ch systems suc (PPS), ceric bromate (TCPB), potassium diperiodatocuprate (III) (PDC), 2,2′- azobisisobutyronitrile (AIBN) and ferrous ammonium sulfate (FAS) have been developed to initiate grafting copolymerization [23–26]. opol es. T g effi s the ion, ng gr f the r. Un aria ultan ve ex g chi aftin ft co dical the ymet an react naly cien ed w l chi ing a graf ymet r w ives umin n de ility ydro scave . Acy –car eriza in w ime well Poly( y N- ly so ft co carr ese ny ki ther ties viny d [2 80% ed w indi graft stab e inc ess a wa meth nditions, which is one of the most abundant organic eing second only to cellulose in the amount produced biosynthesis. Chitin is an important constituent of the in animals, especially in crustaceans, molluscs and also the principal fibrillar polymer in the cell wall of i. As shown in Fig. 1, chitosan is a linear polysaccharide, f glucosamineandN-acetyl glucosamineunits linkedby osidic bonds. The content of glucosamine is called the eacetylation (DD). In fact, in a general way, it is consid- en theDDof chitin ishigher thanabout50% (depending nof thepolymer andon thedistribution of acetyl groups ains), it becomes soluble in an aqueous acidic medium, e conditions, it is named chitosan. The DD also affects adability of this polymer, and for DD above 69% a signif- se in in vivo degradation has been found [1]. In fact, for ylated chitosan, no susceptibility to lysozyme has been ,2]. displays interesting properties such as biocompat- egradability [3,4] and its degradation products are on-immunogenic and non-carcinogenic [5,6]. There- an has prospective applications in many fields such as e, waste water treatment, functional membranes and . However, chitosan is only soluble in few dilute acid hich limits its applications. , therehasbeenagrowing interest in the chemicalmod- chitosan in order to improve its solubility and widen its s [7–9]. Derivatization by introducing small functional he chitosan structure, such as alkyl or carboxymethyl 1] can drastically increase the solubility of chitosan at alkaline pHvalueswithout affecting its cationic charac- tion with moieties bearing carboxylic groups can yield ith polyampholytic properties [12]. Among the various modification, graft copolymerization has been themost ngof chitosanallows the formationof functional deriva- alent binding of a molecule, the graft, onto the chitosan hitosan has two types of reactive groups that can be t, the free amine groups on deacetylated units and sec- ydroxyl groups on the C3 and C6 carbons on acetylated ated units. Recently researchers have shown that after rivation followed by graft modification, chitosan would h improved water solubility, antibacterial and antiox- rties [13,14]. Grafting chitosan is also a common way other properties such as increasing chelating [15] or on properties [16], bacteriostatic effect [17] or enhanc- ion properties [18]. Although the grafting of chitosan properties, it is possible to maintain some interest- eristics such as mucoadhesivity [19], biocompatibility biodegradability [22]. n methods that have been used to chemically mod- will be described in this paper. Some representative f the chemical reactions and experimental conditions presented. Finally the most important applications of ed chitosan-based materials in different fields are also polymerization efore, graft copolymerization is the main method used itosan chemically. In recent years, a number of initiator h as ammonium persulfate (APS), potassium persulfate ammonium nitrate (CAN), thiocarbonationpotassium Graft c enzym graftin such a centrat resulti istics o numbe these v the res sentati graftin 2.1. Gr Gra free ra tists in carbox APS as MAA, were a ing effi improv ypropy obtain water. The carbox initiato derivat chemil chitosa ing ab with h anion groups carbon polym lamide three-d mers s times. tosan b partial Gra also be PPS. Th on ma as a lea proper tion of reporte 70 and increas results in the ing the that th toughn CAN N,N-di ymerization can also be initiated by �-irradiation and he grafting parameters such as grafting percentage and ciency are greatly influenced by several parameters type and concentration of initiator, monomer con- reaction temperature and time. The properties of the aft copolymers are widely controlled by the character- side chains, including molecular structure, length, and til now, many researchers have studied the effects of bles on the grafting parameters and the properties of t grafted chitosan (e.g., Refs. [14,23–26]). Some repre- amples of the previously mentioned methods used for tosan will now be described separately. g initiated by free radicals polymerization of vinyl monomers onto chitosan using initiation has attracted the interest of many scien- last two decades. For example, Sun et al. prepared hyl chitosan-grafted methacrylic acid (MAA) by using initiator in aqueous solution [27]. The effects of APS, ion temperature and time on graft copolymerization sed by determining the grafting percentage and graft- cy. After grafting, the chitosan derivatives had much ater solubility. Similarly, Xie et al. prepared hydrox- tosan-grafted MAA by using APS initiator (Fig. 2) [14], derivative that also presented a good solubility in t copolymerization of maleic acid sodium (MAS) onto hyl chitosan and hydroxypropyl chitosan using APS as reported [28]. The antioxidant activity of these was evaluated as superoxide anion scavengers by escence technology. Compared with chitosan, the graft rivatives were found to have an improved scaveng- against superoxide anion. Graft chitosan derivatives xypropyl groups had relatively higher superoxide nging ability owing to the incorporation of hydroxyl lation of chitosan with maleic anhydride furnishes bon double bonds, which are available for subsequent tion. The copolymerization of the derivative with acry- ater in the presence of APS has been used to obtain nsional crosslinked products [29]. The resulting copoly- ed highly in water with a volume increase of 20–150 3-hydroxy-butylate) could also be introduced into chi- acylation, and the resulting copolymer was found to be luble in water [30]. polymerization of vinyl monomers onto chitosan can ied out using redox initiator systems, such as CAN and systems have been used to produce free radical sites nds of polymers. Poly(vinyl acetate) (PVAc) is known y and water-resistant polymer, which may improve the of chitosan material and hence the graft polymeriza- l acetate onto chitosan by using CAN as an initiator was 3]. The monomer conversion was found to be between after 2h of reaction at 60 ◦C. The grafting efficiency ith increasing amount of chitosan. The experimental cated that the chitosan molecules not only took part copolymerization but also act as a surfactant, provid- ility of the dispersed particles. The data also showed orporation of PVAc to the chitosan chains increased the nd decreased the water absorption of chitosan. s also found to be a suitable initiator for grafting yl-N-methacryloxyethyl-N-(3-sulfopropyl) ammonium N.M. Alves, J.F. Mano / International Journal of Biological Macromolecules 43 (2008) 401–414 403 Fig. 1. Chemical structure of chitosan. [31], poly(acrylonitrile) (PAN) [32], polyacrylamide, poly(acrylic acid) and poly(4-vinylpyridine) [33] onto chitosan. Chitosan was modified with poly(acrylic acid), a well known hydrogel forming polymer, using a grafting reaction in a homoge- neous phase [25]. The grafting was carried out in presence of PPS and FAS as the combined redox initiator system. It was observed that the lev varying the The maxim rather high literature fo This result r tions takes p the whole s effects of th efficiency o presence of version ofH material w may be use synthetic fi A novel to initiate t tosan in alk employed a system use that there i PDC as an employing merization alkali aqueo tors. Graft c by using AIB methacrylate, methyl acrylate, and vinyl acetate were grafted onto chitosan with AIBN in aqueous acetic acid solutions or in aqueous suspensions [26].Here, the graftingpercentageswere generally low [26]. Fenton’s reagent (Fe2+/H2O2) was also successfully used as a redox initiator for grafting methyl methacrylate onto chitosan [36]. Although chitosan is an effective flocculating agent only in acidic the ioni nd b aftin ently sing and c vesti ed d und sorbe g of MA) er c und study itosa g con buty dy, onom the c sed. ant sharp el of grafting could be controlled to some extent by amount of ferrous ion as a co-catalyst in the reaction. um efficiency of grafting attained in this work (52%) is but it is comparablewith values reported recently in the r the grafting of vinyl monomers onto polysaccharides. evealed that inhomogeneous systems thegrafting reac- lace not only on the surface but also in themolecules of ubstrate. Tahlawy and Hudson [34] have discussed the e reaction conditions and temperature on the grafting f 2-hydroxyethylmethacrylate (HEMA) onto chitosan in redox initiators, in this case TCPB. Here, the total con- EMAmonomerwas found to be up to 75%. The resulting as found to increase the hydrophilicity and therefore d as textile finishes enhancing the hydrophilicity of bers. redox system, PDC [Cu (III)–chitosan], was employed he graft copolymerization of methyl acrylate onto chi- ali aqueous solution [35]. In this work, Cu (III) was s an oxidant and chitosan as a reductant in the redox d to initiate the grafting reaction. The result showed s a high grafting efficiency and percentage when using initiator. Since the activation energy of the reaction Cu (III)–chitosan as an initiator is low, the graft copoly- is carried out at a mild temperature of 35 ◦C and in us medium, which makes it superior to other initia- opolymerization onto chitosan has also been attempted N. Some vinyl monomers such as acrylonitrile, methyl media, zwitter acidic a 2.2. Gr Rec mers u chitin was in adsorb was fo the ad graftin (DMAE monom were fo In this onto ch graftin tion of this stu the m when decrea signific ited a Fig. 2. Graft copolymerization of MAA on hydroxy derivatives having side chain carboxyl groups showed c characteristics with high flocculation abilities in both asic media. g using radiation , a great interest has been made to graft natural poly- the radiation method. Grafting of polystyrene onto hitosan using 60Co �-irradiation at room temperature gated [37,38]. The effect of various conditions such as ose, solvent and oxygen on grafting was analysed. It that the grafting yield increased with the increase in d dose. Singh and Roy have also reported radiation chitosan with N,N′-dimethylaminoethylmethacrylate [39]. Parameters such as solvent composition, oncentration, radiation dose rate, and total dose/time to affect the rate of grafting and homopolymerization. , itwas found that adesired levelof graftingofDMAEMA n films was achieved by appropriate selection of these ditions. Yu et al. have reported the graft copolymeriza- l acrylate onto chitosan by using �-irradiation [40]. In an increasing grafting percentage was observed when er concentration and total dose were increased or hitosan concentration and reaction temperature were Under lower dose rates, the grafting percentage had no changes, whereas above 35Gy/min (dose rate) exhib- decrease. Compared with the pure chitosan film, the propyl chitosan. 404 N.M. Alves, J.F. Mano / International Journal of Biological Macromolecules 43 (2008) 401–414 chitosan gra bicity and i The graf has been re the sulfite matrix of g polymeriza mediator) w of the chito study demo chemical bi Singh e the microw tions [42]. The effects Fig. 3. Enzymatic grafting of chitosan with phenol ft poly(butyl acrylate) films have enhanced hydropho- mpact strength. ting of poly(hydroxyethyl methacrylate) onto chitosan ported but in this case by applying UV light [41]. Here, oxidase enzyme was covalently immobilized onto the rafted polymer. After the completion of photo-induced tion reaction, P-benzoquinone (an electron transfer as coupled onto the polymer network for activation san–poly(hydroxyethyl methacrylate) copolymer. This nstrated the feasibility of using chitosan in electro- osensor fabrication [41]. t al. grafted poly(acrylonitrile) onto chitosan using ave irradiation technique under homogeneous condi- They have obtained 70% grafting yield within 1.5min. of reaction variables as monomer and chitosan con- centration, copolymeri with an in also found decreased. 2.3. Enzym There ar in polymer health and hazards ass mental ben exploited to tection step and tyrosinase. microwave power, and exposure time on the graft zation were studied. The grafting was found to increase crease in the monomer concentration. Grafting was to increase up to 80% microwave power and thereafter atic grafting e several potential advantages for the use of enzymes synthesis and modification [43,44]. With respect to safety, enzymes offer the potential of eliminating the ociated with reactive reagents. A potential environ- efit for using enzymes is that their selectivity may be eliminate the need forwaste full protection and depro- s. Finally, enzymes specificity may offer the potential N.M. Alves, J.F. Mano / International Journal of Biological Macromolecules 43 (2008) 401–414 405 tin and chitosan. for precisely polymer fun yield chitos and adhesiv Kumar e lic compou conditions substrates i (pH 6), chito with the na was soluble the degree however, re quinones ca bases or Mi undergo eit oligomer fo reactions be of products The feas hexyloxyph method em o-quinone, with chitosa chemically to prepare m a synthetic properties o chitosan, gr ing the surf 2.4. Cationi Some ye tions onto c polymeriza poly(isobut with contro effect of m number of grafted pol molecular hindrance molecular w polymer wa grafting. Th 3. Special c Besides ducing sma hemical modifications of chitosan and chitin deserve to be d in this chapter due to the potential applications of such n derivatives. These chemical modifications are: phospho- n of chitosan and chitin, combination of chitosan derivatives clodextrins and thiolation of chitosan. osphorylated chitin and chitosan reaction of chitin with phosphorous pentoxide was found water-soluble phosphorylated chitin of high degree of ution (DS), constituting a strategy to overcome this major ck of chitin and its derivatives. Phosphorylated chitin (P- and chitosan (P-chitosan) were prepared by heating chitin osan with orthophosphoric acid and urea in DMF [50–52] . itin and P-chitosan were also prepared by the reaction of or ch acid n in obe ly th n of ity in ylen hitos Fig. 4. Synthesis of phosphorylated chi modifying macromolecular structure to better control ction [45,46]. For instance, enzymaticmodification can anderivativeswithuniquepH-sensitivewater solubility e properties. t al. [45] reported that enzymatic grafting of pheno- nds onto chitosan confer water solubility under basic (Fig. 3). Tyrosinase converts a wide range of phenolic nto electrophilic o-quinones. In slightly acidic media san could be modified under homogeneous conditions tural product chlorogenic acid. The modified chitosan under both acid and basic conditions, even when of modification was low. The chemistry of quinones, mains poorly characterized because of its complexity; n undergo two different reactions to yield either Schiff chael type adducts. Since it is possible for quinones to her or both type of reactions with amines, as well as rming reactions with other quinones, it is common for tween quinones and amines to yield complex mixtures . ibility of using tyrosinase as a catalyst for grafting enol onto the chitosan was also investigated [47]. The ployed tyrosinase to convert the phenol into a reactive which undergoes subsequent non-enzymatic reaction nunderhomogeneous conditions (Fig. 3). Fromthebio- relevant quinones studied so far, it would seempossible aterials of medical interest. For instance, menadione, naphthoquinone derivative having the physiological f vitamin K is particularly prone to rapid reaction with eatly modifying its spectral characteristics and increas- ace hydrophobicity of treated chitosan films [48]. c graft polymerization ars ago, Yoshikawa et al. showed that grafting reac- hitosan can also be performed by using living cationic tion [49]. These authors grafted chitosan with living ylvinyl ether) and poly(2-methyl-2-oxazoline) cation lled molecular weight distribution. In this study, the olecular weight of living polymer cation on the mole grafted polymer was analysed. The mole number of other c include chitosa rylatio with cy 3.1. Ph The to give substit drawba chitin) or chit (Fig. 4) P-ch chitin phonic chitosa found t that on poratio solubil N-meth using c ymer chains was found to decrease with increasing weight of living polymer cation, due to the steric of the functional groups of chitosan with increasing eight of living polymer. The viscosity of the resulting s found to increase with the increasing percentage of is grafted polymerwas also found to be soluble inwater. ases of chitin and chitosan modifications graft copolymerization and derivatization by intro- ll functional groups to the chitosan structure, some Fig. 5. Chemic itosan with phosphorous pentoxide in methane sul- [53,54]. The phosphorylation reactions of chitin and phosphorous pentoxide–methane sulphonic acid were veryefficient [55–58].However, in this case itwas found e P-chitosan with low DS was water soluble. The incor- methylene phosphonic groups into chitosan allowed water under neutral conditions [59]. A water-soluble e phosphonic chitosan (NMPC) was also synthesized an, phosphorous acid and formaldehyde [59]. al structure of N-lauryl-N-methylene phosphonic chitosan (LMPC). 406 N.M. Alves, J.F. Mano / International Journal of Biological Macromolecules 43 (2008) 401–414 Fig. 6. Synthesis of P-chitosan by grafting. A simple methodology for the preparation of a new chitosan derivative surfactant, N-lauryl-N-methylene phosphonic chitosan (LMPC), has been developed [60] (Fig. 5). LMPC incorporated N- methylene phosphonic groups as hydrophilic moieties and lauryl groups as the hydrophobic ones. N-Phosphonomethylation of chitosan reaction was studied and optimized using different reaction conditions [61]. The reaction was conducted with a large excess of both phosphorous acid and formaldehyde at 70 ◦C. The obtained white solid was found to be soluble in neutral and acidic aqueous solutions. Ramos et al. [62] prepared N-methylene phosphonic and car- boxylic chit aldimine fo hydride. Th carboxylic a P-chitos 2-Carboxeth tosan by us (EDC) medi 3.2. Combin Cyclodex to eight (˛ the enzyma The d-gluco to form tor groups at t side of the positions of CDs have g ity, which is and other s binding site is relatively more important side of CD in binding studies [68,69]. The stability of the CD-inclusion complex depends on the polarity of the guest molecule and on the compatibility of the size of the host and that of the guest [70]. Grafting CD molecules into chitosan-reactive sites may lead to a molecular carrier that possess the cumulative effects of inclu- sion, size specificity and transport properties of CDs as well as the controlled release ability of the polymericmatrix [71]. The different methods used to graft CD to chitosan and the inclusion ability, sorp- tion and controlled release properties of the products have been reviewed recently [72]. Grafting of CD onto chitosan has been per- by ith th ive e y am cribe arbo er us Hexa no o (–N nking itosa of � uctiv dific CD nal g of a rafte rmyl d by t, wh in w an a osan (NMPCC) by using NMPC and glyoxallic acid (via rmation) under reduction conditionswith sodiumboro- is new chitosan multidentate ligand presents both nd phosphonic groups [62]. an was also synthesized by graft copolymerization [63]. ylphosphonic acid was covalently attached onto chi- ing 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide ated coupling reaction (Fig. 6). ation of chitosan derivatives with cyclodextrins trins (CDs) are cyclic oligosaccharides built from six =6, ˇ =7, � =8) d-glucose units and are formed during tic degradation of starch and related compounds [64]. se units are covalently linked together by 1,4 linkages us-like structures (Fig. 7). All the secondary hydroxyl he 2- and 3-positions of the glucose units are on one torus, and all the primary hydroxyl groups at the 6- the glucose units are on the other side of the ring [65]. ained prominence in recent years because their cav- hydrophobic in nature, is capable of binding aromatic mall organic molecules, and therefore provides ideal s [66,67]. Selective functionalization at the 6-position easy. However, the secondary side is shown to be the formed EDC w an act primar al. des pling c oligom 1,6- of ami groups crossli in a ch groups Red themo duce a functio mation �-CD-g 2-O-fo followe produc soluble having Fig. 7. Chemical structure of CDs. adopting distinct strategies. A possible way is to react e carboxyl group of carboxymethylated �-CD to form ster intermediate. The intermediate can react with a ine of chitosan to form an amide linkage. Furusaki et d the preparation of a �-CD-grafted chitosan by cou- xymethylated �-CD and a partially deacetylated chitin ing water-soluble EDC [73]. methylene diisocyanate (HMDI), a strong crosslinker r hydroxyl groups since it possesses two isocyanate aCaO) has also been used [72]. It is assumed that the of the hydroxyl groups of chitosan with HMDI resulted n–HMDI complex, which then binds with the hydroxyl -CD to form �-CD-g-chitosan. e amination, one of the major reactions applicable to ation of chitosan, has been successfully applied to intro- residue into chitosan. CD derivatives with aldehyde roups are useful to graft CD into chitosan by the for- Schiff’s base. Tanida et al. reported the synthesis of d chitosan by the formation of a Schiff’s base between methyl-�-CD and chitosan in acetate buffer at pH 4.4, reduction with sodium cyanoborohydride [74]. The ich had a degree of substitution of 37%, was found to be ater at neutral and alkaline conditions. Porous beads bility to form inclusion complexes with specific sub- N.M. Alves, J.F. Mano / International Journal of Biological Macromolecules 43 (2008) 401–414 407 onate strates were of chitosan quent cross were furthe of sodium c grafted chit introductio from the wi situation m been shown of CDs cou constant of Recently chitosan us such as CAN CD onto ch pared by re using CAN esterificatio then the pe in the graf tant produc concentrati reactive site her in tera gues to und sorpt nd h Fig. 8. Reaction scheme for the synthesis of CD itac synthesized by adding an aqueous acetic acid solution into ethanolic aqueous sodium hydroxide and subse- linking with HMDI in DMF [75]. The resulting beads r treated with 2-O-formylmethyl-�-CD in the presence yanoborohydride in acetate buffer at pH 4.4, giving CD- osan beads. In terms of CD-inclusion complexes, the n of a guestmolecule in the cavity classically takes place also ot bond in guest– Due was fo the ad terol a der secondary hydroxyl groups side although the other ay also be encountered, depending on the guest. It has that the steric hindrance effects due to substitution ld result in an important decrease of the association complexes [76]. , a new synthetic route was reported to graft�-CD onto ing an epoxy-activated chitosan [77]. Redox systems, and potassium persulfate have also been used to graft itosan. For example, �-CD-grafted chitosan was pre- acting �-CD itaconate vinyl monomer with chitosan [78]. In this work, �-CD itaconate was prepared by n of �-CD with itaconic acid in a semidry process and ndent double bonds of �-CD itaconate were utilized t copolymerization onto chitosan (Fig. 8). The resul- t was then subjected to crosslinking using different ons of glutaraldehyde. This work showed that not only s play an important role in the sorptionmechanism, but with iodine with p-nitr thiopurine, 3.3. Thiol-c Thiol-co obtained th (Fig. 9). In th [79]. EDC is in the 4.0–6 has been w amines. Thi group of ch boxylic acid a O-acylure the primary Fig. 9. Synthesis of thiol-containing chit -g-chitosan using CAN. teractions, probably physical adsorption and hydrogen ctions, due to the crosslinking agent, and hydrophobic t interactions. the CD moiety present in the chitosan backbone, it that �-CD-grafted chitosan has some selectivity for ion of TNS, bisphenol A, p-nonylphenol, and choles- as the stronger inclusion and slow release ability [72]. CD-grafted polymers form host–guest complexes ophenol, p-nitrophenolate, tert-butylbenzoic acid, 6- p-dihydroxybenzene, and copper ions [72]. ontaining chitosan ntaining chitosan, also called thiolated chitosan, is rough the reaction between chitosan and thiolactic acid is reaction, EDCcanbeused to graft these twomaterials awater-soluble carbodiimide that is typically employed .0 pH range. It is a zero-length crosslinking agent that idely used to couple carboxylic acid groups to primary olactic acid is covalently attached to the primary amino itosan under the formation of amide bonds. The car- moieties of thiolactic acid are activated by EDC forming a derivative as an intermediate product that reacts with amino groups of chitosan. When compared with other osan. 408 N.M. Alves, J.F. Mano / International Journal of Biological Macromolecules 43 (2008) 401–414 f chit modified ch advantageo hesive and solutions of physiologic 4. “Smart c hydrogels e Smart hy phase chan tors. Among been the m applicable i temperatur tive thermo temperatur fluids, due t ing a LCST injectable a a well kno around 32 ◦ below the water. Great at cations, to with uniqu and biologi thermo-res polymeric c polysacchar have been c due to the p polymer w stimuli-resp vehicles tha in the hum polymeric g al m som aft co roge s typ of 25 g ch ent orph BN, 2 , N,N, chniq Fig. 10. Reaction scheme for the preparation o itosan materials, thiolated chitosans have numerous us features, such as significantly improved mucoad- permeation enhancing properties [80–85]. Moreover, thiolated chitosans display in situ gelling properties at al pH values [82]. hitosan”: example of new chitosan-based xhibiting temperature-responsive behaviour drogels canundergo a reversible discontinuous volume ge in response to various external physicochemical fac- them, temperature and pH-responsive hydrogels have ost widely studied, because these two factors can be n vivo. Polymer solutions have a lower critical solution chemic well as 4.1. Gr Hyd variou range swellin depend and m APS, AI (AIBA) tion te e (LCST) contract byheating above the LCST. Thesenega- -reversible hydrogels can be tuned to be liquid at room e and to undergo gelation when in contact with body o an increase in temperature. Therefore, polymers hav- below human body temperature have a potential for pplications. Poly(N-isopropylacrylamide) (PNIPAAm) is wn thermally reversible polymer, exhibiting a LCST C in aqueous solution [86]. PNIPAAm hydrogels swell LCST and shrink above the LCST, when immersed in tention has been paid, especially for biomedical appli- the development of stimuli-responsive polymeric gels e properties such as biocompatibility, biodegradability cal functionality. They may be prepared by combining ponsive polymers such as PNIPAAm with natural based omponents, to form smart hydrogels [87–91]. Some ides, such as chitosan, alginate, cellulose and dextran, ombined with thermo-responsive materials. Moreover, H-sensitive character of chitosan, combination of this ith a thermo-responsive material will produce dual- onsive polymeric systems that can be used as delivery t respond to localized conditionsof pHand temperature an body. A review on natural based stimuli-responsive els has been recently published [92]. Next the twomain Fig. 10 show PNIPAAm u Chitosan soapless em AIBA may b the copolym pH value. Graft co have been prepared b swelling rat pH and tem Kimet a epoxy-term UV irradiat tosan were The grafting increasing dose. The s increased w cated that t amount of t Graft co sation reac osan-g-PNIPAAm. odifications used to prepare these smart hydrogels as e relevant examples are presented. polymerized hydrogels ls prepared by graft copolymerization of NIPAAm onto es of polysaccharides have shown a LCST in the –34 ◦C. Properties such as volume phase transfer and aracter of the hydrogels, were found to be mainly on their polymers weight ratio, crosslinking density ology. A number of initiator systems, such as CAN, ,2′-azobis-(2-methylpropionamidine) dihydrochloride N′,N′-tetramethylethylene diamine (TEMED) and radia- ues have been reported to graft NIPAAm onto chitosan. s the reaction that can be used to prepare chitosan-g- sing CAN [93]. -g-PNIPAAm particles can also be synthesized by a ulsion copolymerization method [94]. Either APS or e used as initiators. In this case the swelling ratio of er decreased with increasing crosslinking density and polymers based on a maleilated chitosan and NIPAAm synthesized by UV radiation. Maleilated chitosan was y reacting chitosan with maleic anhydride [95]. The ioofmaleilated chitosan-g-PNIPAAmdependedonboth perature of the aqueous solution. l. synthesized hydrogels based on grafting chitosanwith inated poly(dimethylsiloxane) (PDMS) also by using ion [96]. Hydrogels based on PNIPAAm-grafted chi- obtained but in this case by applying �-irradiation [97]. percentage and the grafting efficiency increased with the monomer concentration and the total irradiation welling ratios of these chitosan-g-PNIPAAm hydrogels ith the increase of the grafting percentage, which indi- he swelling behaviour of the hydrogels depends on the he grafted branches. polymers can also be prepared by using the conden- tion in the presence of EDC. Lee et al. synthesized N.M. Alves, J.F. Mano / International Journal of Biological Macromolecules 43 (2008) 401–414 409 comb-type terminated catalyzes th acid group groups of of carboxy tosan is sh comb-type sensitivity chitosan m tively. Recently multi-respo because of component pared from Fig. 11. Preparation of carboxyl-terminated PNIPAAm and c graft hydrogels, composed of chitosan and carboxyl- PNIPAAm by using this carbodiimide [98]. EDC e formation of amide bonds between the carboxylic s of carboxyl-terminated PNIPAAm and the amine chitosan. The reaction scheme for the preparation l-terminated PNIPAAm, and its grafting onto chi- own in Fig. 11. In the swelling/deswelling behaviour, graft hydrogels showed rapid temperature and pH because of the free-ended PNIPAAm attached to the ain chain and the chitosan amine group itself, respec- , microgels with more complex structures, such as a nsive core–shell, have received increasing attention the tunable properties of the individual responsive s. Various types of core–shell microgels have been pre- the PNIPAAm-grafted polysaccharides. Leung et al. [99,100] de temperatur PAAm and co-NIPAAm acid (MMA [101]. Here was prepar was prepare Besides PNIPAAm w sensitive gr case of thos based on p (PPO), know et al. prepa on chitosan omb-type graft hydrogel. veloped smart microgels that consist of well-defined e-sensitive coreswith pH-sensitive shells based on PNI- chitosan. The properties of crosslinked poly(chitosan- )/poly[methacrylic acid (MAA)-co-methyl methacrylic )] core–shell type copolymer particles were examined , the crosslinked copolymer of NIPAAm and chitosan ed as the core, and the copolymer of MAA and MMA d as the shell. the many works that propose the association of ith chitosan, other few examples of distinct thermo- aft copolymerized hydrogels can be found. This is the e systems that combine amphiphilic block copolymers oly(ethylene oxide) (PEO) and poly(propylene oxide) n as poloxamers, with chitosan. For instance, Creuzet red this kind of hydrogels by grafting PEO–PPO blocks [102]. 410 N.M. Alves, J.F. Mano / International Journal of Biological Macromolecules 43 (2008) 401–414 4.2. Chemically crosslinked blends Stimuli-responsive hydrogels can also be obtained by blend- ing biopoly various me assembly o is synthesiz system is c component the linear f form a gel t been well d soluble pol such as glu in the pres mers seem Somework tosan/gluta is this kindo tosan and P increases as increases. K based on ch ural crossli hydrogels s makes the g A full-IP tion of a me network wi The author including t transition b the swellin microstruct ing semi-IP swell faster swelling rat temperatur 5. Applicat The pot important fi neering and attempt is and future p 5.1. Drug de As said i cal characte toxicity [5,6 enzymes, e these favor tives in dru years. More tant that ch properties e macromole Many w and its der has been s trimethyl c feature of a drug delivery [10,108,109]. Acrylic acid grafts of chitosan as pos- sible means of creating hydrophilic and mucoadhesive polymers, have been reported recently [27,110]. Chitosan-grafted poly(acrylic artic hyd repa nked teroi itis [1 ldeh cha ymet was tissu meri omy e w ng m been hitos n [1 as a roph ed ch ions noth of b obta y sys odifi cy o n se alian xes mpl alian f bio r to nd p ue f repa xy-om ed in d in n (P ated s we t 9 w ing t afted d DN ation ficien cells ondu cy. y rec AM were ccess ffere mon etha ation mer mers with synthetic thermo-responsive materials by chanisms of chemical crosslinking. When we have an f two crosslinked polymers and at least one of which ed and crosslinked in the presence of the other, this alled an interpenetrated network (IPN). If only one of the assembly is crosslinked leaving the other in orm, the system is termed as semi-IPN. The ability to hrough the crosslinking of chitosan with PNIPAAm has ocumented. Many hydrogels are formed from water- ymers by crosslinking them using crosslinking agents taraldehyde or polymerizing hydrophilic monomers ence of a crosslinker. Chemically crosslinked poly- to be one of the candidates to improve wet strength. s reporting the preparation of PNIPAAm-containing chi- raldehyde gels can be found [103,104]. Another example f blends is glutaraldehyde crosslinked semi-IPNsof chi- AN [105]. Of course, the water uptake of these systems the molar ratio of the hydrophilic groups of chitosan hurma et al. reported the preparation of semi-IPNs itosan and poly(vinyl pyrrolidone) (PVP) by using a nat- nking agent, genipin [106]. It was found that PVP-rich welled themost, because increasing the amounts of PVP el structure less compact, and more inhomogeneous. N hydrogel was synthesized by the chemical combina- thylenebis(acrylamide) (MBAM) crosslinked PNIPAAm th a formaldehyde crosslinked chitosan network [107]. s [107] demonstrated that the properties of the gels, he extractability of PNIPAAm within it, the phase ehaviour, the swelling dynamics in aqueous phase, g behaviour in ethanol/water mixtures and even the ure were quite different from those of the correspond- N hydrogels. It was found that the semi-IPN hydrogels than the corresponding full-IPN hydrogels, and that the io for the semi-IPN hydrogels is almost independent of e [107]. ions for modified chitosan materials ential applications of modified chitosan in various elds, such as environment, drug delivery, tissue engi- other biomedical application are here discussed. An also made to discuss some of the current applications rospects of modified chitosan. livery n Section 1, chitosan has interesting biopharmaceuti- ristics such as pH sensitivity, biocompatibility and low ]. Moreover, chitosan is metabolised by certain human specially lysozyme, and is biodegradable [5]. Due to able properties, the interest in chitosan and its deriva- g delivery applications has been increased in recent over, in such applications it is also extremely impor- itosan be hydro-soluble and positively charged. These nable it to interact with negatively charged polymers, cules and polyanions in an aqueous environment. orks related with potential applications of chitosan ivatives can be found in literature. For instance, it hown that chitosan and its derivatives, such as N- hitosan or N-carboxymethyl chitosan, have the special dhering to mucosal surfaces, being useful for mucosal acid) p ers for et al. p crossli a nons arthrh glutara calcium carbox groups cerous of poly like ble Som apy usi it has lated c chitosa tosan w by hyd alkylat attract In a ponent and to deliver acid-m efficien chitosa mamm comple DNAco mamm posedo in orde time a techniq [117] p metho improv vitro an chitosa formul sphere at leas by vary PEG-gr plasmi conjug tion ef tumor being c efficien Ver a PAM chains and su two di was de dexam ferenti dendri les have been proposed as hydrophilic drug carri- rophilic drugs and sensitive proteins [111]. Kumbar red microspheres of polyacrylamide-grafted-chitosan with glutaraldehyde to encapsulate indomethacin (IM), dal anti-inflammatory drug used in the treatment of 12]. Microspheres of grafted chitosan crosslinked with yde were prepared to encapsulate nifidifine (NFD), a nnel blocker and an antihypertensive drug. N-Lauryl hyl chitosan with both hydrophobic and hydrophilic studied in connection with the delivery of taxol to can- es [113]. Other examples are related to the production c vesicles for encapsulation of hydrophobic compounds cin [114]. orks related with intracellular delivery for gene ther- odified chitosan-based materials were reported. In fact argued that the most important application of alky- an is in DNA delivery such as proven with dodecyl 15]. The high transfection efficiency of alkylated chi- ttributed to the increasing entry into cells facilitated obic interactions and easier unpacking of DNA from itosan carriers, due to the weakening of electrostatic between DNA and alkylated chitosan. er work [116], deoxycholic acid, which is the main com- ile acids, was used to modify chitosan hydrophobically in self-assembling macromolecules for non-viral gene tem. The self-aggregateDNA complex fromdeoxycholic ed chitosan was shown to enhance the transfection ver monkey kidney cells [116]. The feasibility of these lf-aggregates for the transfection of genetic material in cellswas investigated. Self-aggregates can formcharge when mixed with plasmid DNA. These self-aggregate exes are considered tobeuseful for transfer of genes into cells in vitro and served as good delivery system com- degradablepolymericmaterials. PEGylationof chitosan increase its solubility, elongate the plasma circulation rolong the gene transfer has been another proposed or the sustained DNA release. For example, Zhang et al. red chitosan–DNA complexes conjugated with alpha- ega-succinimidyl PEG, and the gene expression was comparison with the chitosan–DNA complex both in vivo. Microspheres physically combining PEG-grafted- EG-g-CHI) with poly(lactide-co-glycolide) (PLGA) were by Yun et al. [118]. They reported that these micro- re capable of sustained release of PEG-g-CHI/DNA for eeks, and the rate of DNA release was not modulated he amount of PEG-g-CHI. In another work [119] folate- chitosan was synthesized and proposed for targeted A delivery to tumor cells. The authors found that folate in this system significantly improved gene transfec- cy due to promoted uptake of folate receptor bearing . In vitro and in vivo studies of gene transfection are cted in the laboratory to evaluate its gene transfection ently novel water-soluble nanoparticles that consist of dendrimer core with grafted carboxymethyl chitosan successfully synthesized [120]. The non-cytotoxicity ful internalization of these dendrimer nanoparticles by nt types of cells, i.e., cell lines and primary cultures, strated in this work. The authors also showed that the sone-loaded nanoparticles induced the osteogenic dif- of rat bone marrow stem cells in vitro. So, these novel nanoparticles may be used as targeted drug-delivery N.M. Alves, J.F. Mano / International Journal of Biological Macromolecules 43 (2008) 401–414 411 carriers to cover a wide range of applications that involve the effi- cient intracellular delivery of biological agents to modulate the behaviour of cells. Thiol-co used as a co It has been be used as tration sinc the stomach Chitosan been propo to the prese tems provid Finally, s drug loadin In particula shown dru and temper This kind of ery. For ins NIPAAm/vin examined t cells agains transfection by dissociat ing the cult lipofectami fection [126 5.2. Tissue e The pres based on th matrixes. A serveas the have been r als because without infl TEapplicati ble for elect proteoglyca Some re tosan and t been report grafted PLL thesefilms ratio of PLL of biodegra chitosanwi of two cell atocytes), c and tended same speed to clarify th differentiat phology and in tissue en Very rec posed as ti release carr structure, in ated within It has be an adequate it seems po by pouring a liquid thiolated chitosan cell suspension in a mold. Furthermore, liquid polymer cell suspensions may be applied by injection forming semi-solid scaffolds at the site of tissue damage. see faces dem hosp port sans ts, sh the ater stron smar PLL 6], w ther for T ition oun repa ition d m dditi chi cel ratur sive of m mers l app g ves timi tosan app ostat e tet tibac der n egat tivity esse s to mbr syst iodon DTA 0]. C d ant osa, s [14 osan ton r ount ]. as be be us pati effi card that may e us ntaining chitosan beadswere synthesized in order to be ntrolled and pH-responsive drug delivery system [79]. shown that P-chitosan beads have a great potential to controlled drug release systems through oral adminis- e the release in the highly acidic gastric fluid region of is avoided [63,121]. -based systems bearing �-cyclodextrin cavities have sed as a matrix for controlled release [122,123]. Due nce of the hydrophobic�-cyclodextrin rings, these sys- e a slower release of the entrapped hydrophobic drug. timuli-responsive hydrogels have shown an improved g capacity, and a sustained release behaviour [92]. r, systems that combine chitosan and PNIPAAm have g release profiles that can be controlled by both pH ature [124,125], constituting very promising materials. smart systems has also been proposed for gene deliv- tance, Sun et al. [126] coupled a carboxyl-terminated yl laurate (VL) copolymer with chitosan (PNVLCS) and he gene expression of PNVLCS/DNA complexes in C2C12 t temperature change. The results indicated that the efficiency of PNVLCS/DNA complexes was improved ion of the gene from the carrier by temporarily reduc- ure temperature to 20 ◦C. By contrast, naked DNA and ne did not demonstrate thermo-responsive gene trans- ]. ngineering ent generation of tissue engineering (TE) research is e seeding of cells onto porous biodegradable polymer primary factor is the availability of good biomaterials to temporarymatrix. Recently, chitosanand itsderivatives eported as attractive candidates for scaffolding materi- they degrade as the new tissues are formed, eventually ammatory reactions or toxic degradation [116,127]. In ons thecationicnatureof chitosan isprimarily responsi- rostatic interactions with anionic glycosaminoglycans, ns and other negatively charged molecules. search works where the biological properties of chi- he mechanical properties of PLLA are combined have ed. The in vitro fibroblast static cultivation on chitosan- A films for 11 days showed that the cell growth rate on was faster than in chitosan anddecreasedwhen the feed A to chitosan increases [128]. Surface functionalization dable PLLAwas achieved by plasma coupling reaction of th PLLA [129]. Theproliferation andmorphology studies lines, L-929 (mouse fibroblasts) and L-02 (human hep- ultured on this surface showed that cells hardly spread to become round, but could proliferate at almost the as cells cultured on glass surface. This insight will help e mechanism of the switch between cell growth and ion. Thisgraftedpolymercanbeused tocontrol themor- function of cells, and hence has potential applications gineering. ently novel PLLA–chitosan hybrid scaffolds were pro- ssue engineering scaffolds and simultaneously drug iers [130]. In this innovative system a chitosan porous which cells and tissues would mostly interact, is cre- the pore structure of a stiffer PLLA scaffold. en shown that thiolated chitosan [81,131] can provide scaffold structure: due to the in situ gelling properties ssible to provide a certain shape of the scaffold material So they Sur in vitro cium p been re P-chito cemen namely start m phate to the grafted pH [13 Ano tosan recogn sugar-b They p recogn cells an In a grafted trolling tempe respon culture copoly clinica treatin 5.3. An Chi healing bacteri diamin the an that un gram-n bial ac makes or bind cellme healing of per with E use [14 showe aerugin S. aureu of chit chophy the am pH [17 It h tial to biocom growth used in strated HEMA tial to b m to be promising candidates for such applications. that can induce the formation of an apatite layer onstrate improved bone-binding properties and cal- hate growth on P-chitin fibers and P-chitosan films has ed after soaking with Ca(OH)2 [132,133]. Water-soluble have been mixed with different calcium phosphate owing an improvement in their properties [134,135], mechanical strength, setting time, dissolubility of the ials of the cements and they also bind calcium phos- gly afterwards. Moreover it has been shown that due t nature of chitosan, the apatite formation of chitosan- A films reinforced with Bioglass® can be controlled by hich could also have relevance in bone TE applications. approach regarding the chemical modification of chi- E applications has been to introduce the specific of cells by sugars. A recent example of the synthesis of d chitosan can be found in the work of Kim et al. [137]. red mannosylated chitosan (MC) having the specific to antigen presenting cells such as B-cells, dendritic acrophages. on to applications in controlled drug release, PNIPAAm- tosan-based materials have been exploited for con- l adhesion/detachment by changing the incubation e above or below its LCST [138,139]. Temperature- chitosan-graft-PNIPAAm [139] were applied for the esenchymal stem cells (MSCs). Chitosan-g-PNIPAAm with chondrogenic MSCs revealed the possibility of lications, particularly as cell therapy technologies for icoureteral reflux [138]. crobial agents and other biomedical applications derivatives present interesting properties for wound- lications, because such materials can exhibit enhanced ic activity with respect to pure chitosan. Ethylene raacetic acid (EDTA) grafted onto chitosan increases terial activity of chitosan by complexing magnesium ormal circumstances stabilizes the outer membrane of ive bacteria [140]. The increase in chitosan antimicro- is also observed with carboxymethyl chitosan, which ntial transition metal ions unavailable for bacteria [141] the negatively charged bacterial surface to disturb the ane [142]. Therefore, thesematerials are used inwound- ems, such as carboxymethyl chitosan for the reduction tal pockets in dentistry [141] and chitosan-grafted as a constituent of hydro-alcoholic gels for topical hitosan and chitooligosaccharide-grafted membranes ibacterial activity against Escherichia coli, Pseudomonas methicilin-resistant Staphylococcus aureus (MRSA), and 3]. Also, it was observed that the antimicrobial activity and graft copolymers against Candida albicans, Tri- ubrum, and Trichophyton violaceum depends largely on and type of grafted chains, as well as on the changes of en shown that chitosan derivatives have great poten- ed in other biomedical applications. As a result of the ble properties such as good blood compatibility and cell ciency, grafted chitosan materials have potential to be io-vascular applications [144,145]. It has been demon- the permeability of chitosan membranes grafted with be controlled through plasma-treatment having poten- ed in dialysis [146]. 412 N.M. Alves, J.F. Mano / International Journal of Biological Macromolecules 43 (2008) 401–414 5.4. Adsorption of metal ions The high sorption capacities of modified chitosan for metal ions can be of g treatment o derivatives ions by inc bone. The n increase th metal sorpt sorption sel The gra regarded a properties to design c [147,148]. A boxylic fun anhydrides The graf subject of m resins [150 fully tested metals, owi metal ions. to improve [153]. N-Haloc hypochlorit many other by reacting acid exhib [155]. P-chitin was found of the other line earth m phosphate g ered that th even more The com metal ion s also been a the produc heavy meta use of dend for this kin of chitosan dendrimer- these syste when the g equal to 2 a for Au3+ an terminated ones [161]. A great d ether on chi Schiff’s base mesocyclic tivity for C properties crown ethe (CTDA)was these new t cations for t environmen 5.5. Dye removal Chitosan, due to its high contents of amine and hydroxyl func- grou clud ol [1 catio ] rec deriv hobi yl gr in a catio ith catio [168 tosan to fo s, an t ma ile dy n de sorp er an clus diffe ensiv wed in a s so n de wate uch a sue e nces Tomih W. Ch 39–21 Kuma v. 104 . San itosan ns, El A.A. M . Bers Kurita tt. 27 Sashi Heras Jayaku Lu, L. 07–38 A.A. M 9–214 .M. X 99–17 .M. Xi K. Yan Chen, O. Jun 13–17 . Than 7–126 S. Hof (1997 A. Task Ono, Y reat use for the recovery of valuable metals or the f contaminated effluents. A great number of chitosan have been obtained with the aim of adsorbing metal luding new functional groups onto the chitosan back- ew functional groups are incorporated into chitosan to e density of sorption sites, to change the pH range for ion and to change the sorption sites in order to increase ectivity for the target metal. fting of carboxylic functions has frequently been s an interesting process for increasing the sorption of chitosan. Usually, the aim of these modifications is helating derivatives for the sorption of metal cations nother way to achieve the grafting of carbonyl and car- ctions may consist in reacting chitosan with carboxylic [149]. ting of sulphur compounds on chitosan has been the any studies for the design of chelating chitosan-based –152]. These sulphur derivatives have been success- for the recovery of mercury and the uptake of precious ng to the chelating affinity of sulphur compounds for Sulphonic groups have been also grafted on chitosan sorption capacity for metal ions in acidic solutions hitosans prepared by reacting chitosan with sodium e are good flocculants for metallic oxides along with contaminants [154]. N-Chloroacetyl chitosan, prepared chitosan with chloroacetic anhydride in chloroacetic ited high affinity for cations such as Cu2+, Fe3+ and P-chitosan have a strong metal-binding ability. It that their adsorption of uranium is much greater than heavy metal ions [52]. Also, the binding ability to alka- etals was significantly enhanced by the introduction of roups [156]. In fact, Schwarzenbach et al. [157] consid- e phosphonic complexing agents were as effective or than those containing carboxylic groups. bination of CDs with chitosan for manufacturing new orbents, typically by using a Schiff’s base reaction, has dopted [158,159]. Other very recent approach involves tion and use of thiolated chitosan films for aqueous l ions detection, in particular for mercury [160]. The rimers combinedwith chitosan is currently under study d of applications [161]. Qu et al. synthesized a series derivatives by grafting ester- and amino-terminated likePAMAMintochitosan [161]. The results showedthat ms were completely insoluble in dilute acid solutions enerations of grafted dendrimers were greater than or nd that they exhibited excellent adsorption capabilities d Hg2+. Moreover the adsorption capabilities of amino- products were higher than those of ester-terminated eal of attention has been paid to the grafting of crown tosan formanufacturingnewmetal ion sorbents using a reaction [162,163]. Aza crownether-graft-chitosan and diamine-g-chitosan crown ether showed high selec- u2+ in presence of Pb2+ [164]. The static adsorption of Ag+, Cd2+, Pb2+, and Cr3+ by chitosan hydroxyl aza r (CTS-DA) and chitosan dihydroxyl mesocyclic diamine reported [15,165]. So, it is expected that in a near future ype chitosan crownetherswill havewide ranging appli- he separation and concentration of heavy metal ions in tal analysis. tional dyes in naphth ity are al. [169 fonate hydrop Carbox donors adsorb beadsw tion of Y (BB) Chi ability pound sorben of text chitosa rate of polym [166]. 6. Con The the ext ter, sho soluble aqueou chitosa waste tions s and tis Refere [1] K. [2] Y. 21 [3] R. Re [4] P.A Ch tio [5] R. [6] P.C [7] K. Le [8] H. [9] A. [10] R. [11] G. 38 [12] R. 19 [13] W 16 [14] W [15] Z. [16] S. [17] B. 17 [18] M 11 [19] A. 38 [20] R. [21] K. ps, has an extremely high affinity for many classes of ing disperse, direct, reactive, anionic, vat, sulphur and 66,167]. The only class for which chitosan has low affin- nic dyes [167,168]. To overcome this problem Crini et ently suggested the use of N-benzyl mono- and disul- atives of chitosan in order to enhance its cationic dye c adsorbent properties and to improve its selectivity. oups grafted onto chitosan may also serve as electron n alkaline environment to confer chitosan the ability to nic dyes from aqueous solutions. Modified chitosan gel phenol derivativeswere found to be effective in adsorp- nic dyes, such as crystal violet (CV) andBismarck brown ]. grafted with CDs, in particular �-CD derivatives, have rm complexes with a variety of other appropriate com- d are very promising materials for developing novel trices [16,170]. Martel et al. showed that the adsorption es from the effluent can be carried out with �-CD-g- rivatives [166]. Moreover, these systems have superior tion and global efficiency than that of parent chitosan d of the well-known cyclodextrin–epichlorohydrin gels ions rent chemical modifications of chitosan developed by e work of many researchers, summarized in this chap- that it is possible to obtain chitosan derivatives not only cidic aqueous solutions but also in neutral and basic lutions. Moreover it has been demonstrated that these rivatives present the adequate properties for safe use in r treatments and, in particular, in biomedical applica- s controlled delivery of drugs or other bioactive agents ngineering. ata, Y. Ikada, Biomaterials 18 (1997) 567–575. o, Y.N. Cho, S.H. Chung, G. Yoo, S.W. Ko, Biomaterials 20 (1999) 45. r,M.N.V.Muzzarelli, R.A.A.Muzzarelli, C.H. Sashiwa, A.J. Domb, Chem. (2004) 6017–6084. ford, in: G. Skjak-Braek, T. Anthonsen, P.A. Sanford (Eds.), Chitin and -sources, Chemistry, Biochemistry, Physical Properties and Applica- sevier, London, 1989, pp. 51–70. uzzarelli, Cell Mol. Life Sci. 53 (1997) 131–140. ch, B.Nies, A. Liebendorfer, J.Mater. Sci.Mater.Med. 6 (1995) 231–240. , T. Kojima, T. Munakata, H. Akao, T. Mori, Y. Nishiyama, et al., Chem. (1998) 317–318. wa, Y. Shigemasa, Carbohydr. Polym. 39 (1999) 127–138. , N.M. Rodriguez, V.M. Ramos, Carbohydr. Polym. 44 (2001) 1–8. mar, R.L. Reis, J.F.Mano,Mater. Sci. Forum514–516 (2006) 1015–1019. Kong, B. Sheng, G. Wang, Y. Gong, X. Zhang, Eur. Polym. J. 43 (2007) 18. uzzarelli, M. Emmanueli, S. Mariotti, Carbohydr. Res. 107 (1982) . ie, P.X. Xu, W. Wang, Q. Lu, Bioorg. Med. Chem. Lett. 11 (2001) 03. e, P.X. Xu, W. Wang, Q. Lu, Carbohydr. Polym. 50 (2002) 35–40. g, Y. Yuan, J. Appl. Polym. Sci. 82 (2001) 1838–1843. Y. Wang, J. Polym. Sci. 82 (2001) 2414–2421. g, C.H. Kim, K.S. Choi, Y.M. Lee, J.J. Kim, J. Appl. Polym. Sci. 72 (1999) 19. ou, J.C. Verhoef, H.E. Junginger, Adv. Drug Deliv. Rev. 52 (2001) . fman, G. Chen, X.Wu, Z. Ding, B. Kabra, K. Randeri, et al., Polym. Prepar. ) 524–525. er, B.J. Connell, S.J. Ross, C.M. Elson, Lab. Anim. 32 (1998) 270–275. . Saito, H. Yura, K. Ishikawa, J. Biomed.Mater. Res. 49 (2000) 289–295. N.M. Alves, J.F. Mano / International Journal of Biological Macromolecules 43 (2008) 401–414 413 [22] D.K. Singh, A.R. Ray, Carbohydr. Polym. 36 (1998) 251–255. [23] T.M. Don, C.F. King, W.Y. Chiu, J. Appl. Polym. Sci. 86 (2002) 3057–3063. [24] S.Y. Kim, S.M. Cho, Y.M. Lee, S.J. Kim, J. Appl. Polym. Sci. 78 (2000) 1381–1391. [25] M.Y. Pe 923–930 [26] H.S. Bla 641–656 [27] T. Sun, P [28] T. Sun, W [29] L.A. Ber Chem. E [30] M. Yalpa 24 (1991 [31] J. Zhang [32] A. Pourj (2003) 2 [33] Y. Yilma [34] K.E.L. Ta [35] Y. Liu, Z. [36] A. Lagos [37] L. Pengf [38] Y. Shige (1982) 5 [39] D.K. Sin [40] L.L. Yu, Y [41] L.T. Ng, J [42] V. Singh 820–825 [43] J.S. Dord [44] D.L. Kap (Eds.), P 1998, pp [45] G. Kuma [46] K. Yama Biomacr [47] T. Chen, (2000) 5 [48] C. Muzz 223–229 [49] S. Yoshi 1883–18 [50] S.J. Ham 42–51. [51] S.J. Ham Biophys [52] T. Sakag [53] N. Nishi 6 (1984) [54] N. Nishi Biol. Ma [55] O. Somo [56] K. Kaifu, [57] N. Nishi 919–923 [58] N. Nishi [59] A. Heras 1–8. [60] J. Sludd 377–382 [61] N.M. Ra Polym. 5 [62] V.M. Ram Mater. 5 [63] R. Jayaku [64] H.J. Busc 40 (2001 [65] T. Loftss [66] V. Laine Perkin T [67] K. Uekam [68] R.S.R. Pa (2005) 2 [69] S. Rozou [70] J. Szejtli [71] R. Auzel [72] M. Praba [73] E. Furus 29–34. [74] F. Tanida (1998) 5 [75] T. Tojim Polym. 4 [76] V. Laine Perkin T [77] X. Zhang [78] M.A.Gaffar, S.M.E. Rafie, K.F.E. Tahlawy, Carbohydr. Polym. 56 (2004) 387–396. [79] R. Jayakumar, R.L. Reis, J.F. Mano, Drug. Deliv. 14 (2007) 9–17. [80] A.B. Schnurch, T.E. Hornof, Sci. Pharm. 69 (2001) 109–118. E. Kast . Horn 5–190 B. Sch B. Sch E. Clau G. Sch Bokia Kubo 8–805 M. Low hang Penic omate . Praba . Lee (2004 F. Lee, 004) 3 . Don . Kim, 002) 2 Cai, Z –30. . Lee 12–26 .F. Leu 19–18 .F. Leu L. Lin, Creuz –38. . Wan em. 3 .Goy acrom . Kim, 21–27 . Khur . Wan L. Lue nginge . Than 001) 3 Y. Jian L. Shan . Kum 25–15 Yoshi 995) 1 Miwa s. 15 ( .G. Liu . Kim Zhang ochem . Yun 59–13 Chan, . Oliv sta, J.F . Win . Praba H. Kra A. Lore rg, J. C Bhatt 005) 6 . Sun, 2–980 Tuzla 1–819 Yao, W Ding, 59–10 . Praba s. Par Kast, W .R. Mu shizaw K. Var meya dram, J. Retuert, R. Quijada, Macromol. Chem. Phys. 201 (2000) . ir, J. Guthrie, T.K. Law, P. Turkington, J. Appl. Polym. Sci. 33 (1987) . . Xu, Q. Liu, J. Xue, W. Xie, Eur. Polym. J. 39 (2003) 189–192. . Xie, P. Xu, Carbohydr. Polym. 58 (2004) 379–382. kovich, M.P. Tsyurupa, V.A. Davankov, J. Polym. Sci. Part A: Polym. d. 21 (1983) 1281–1287. ni, R.H. Marchessault, F.G. Morin, C.J. Monasterious, Macromolecules ) 6046–6049. , Y. Yuan, J. Shen, S. Lin, Eur. Polym. J. 39 (2003) 847–850. avadi, G.R. Mahdavina, M.J.Z. Mehr, H. Omidian, J. Appl. Polym. Sci. 88 048–2054. z, H. Caner, H. Hasipoglu, O. Yilmaz, Eur. Polym. J. 34 (1998) 493–497. hlawy, S.M. Hudson, J. Appl. Polym. Sci. 82 (2001) 683–702. Liu, Y. Zhang, K. Deng, J. Appl. Polym. Sci. 89 (2003) 2283–2289. , J. Reyes, J. Polym. Sci. Part A: Polym. Chem. Ed. 26 (1988) 985–991. ei, Z. Maolin, W. Jilan, Radiat. Phys. Chem. 61 (2001) 149–153. no, K. Kondo, K. Takemoto, J. Macromol. Sci. Pure Appl. Chem. A17 71–583. gh, A.R. Roy, J. Appl. Polym. Sci. 66 (1997) 869–877. . He, L. Bin, F. Yue, J. Appl. Polym. Sci. 90 (2003) 2855–2860. .T. Guthrie, Y.J. Juan, H. Zhao, J. Appl. Polym. Sci. 79 (2001) 466–472. , D.N. Tripathi, A. Tiwari, R. Sanghi, J. Appl. Polym. Sci. 95 (2005) . ick, Trends Biotechnol. 10 (1992) 287–293. lan, J.S. Dordick, R.A. Gross, G. Swift, in: R.A. Gross, D.L. Kaplan, G. Swift roceedings of ACS Symposium Series, vol. 684, ACS, Washington, DC, . 2–16. r, P.J. Smith, G.F. Payne, Biotechnol. Bioeng. 63 (1999) 154–165. da, T. Chen, G. Kumar, O. Vesnovsky, L.T.D. Topoleski, G.F. Payne, omolecules (2000) 252–258. G. Kumar, M.T. Harris, P.J. Smith, G.F. Payne, Biotechnol. Bioeng. 70 64–573. arelli, R.A.A. Muzzarelli, Trends Glycosci. Glycotechnol. 14 (2002) . kawa, T. Takayama, N. Tsubokawa, J. Appl. Polym. Sci. 68 (1998) 89. odrakas, C.W. Jones, F.C. Kafatos, Biochim. Biophys. Acta 700 (1982) odrakas, S.A. Asher, G.D. Mazur, J.C. Regier, K.C. Kafatos, Biochim. . Acta 703 (1982) 216–222. uchi, T.Hirokoshi,A.Nakajima,Agric. Biol. Chem.45 (1981)2191–2195. , S. Nishimura, A. Ebina, A. Tsutsumi, S. Tokura, Int. J. Biol. Macromol. 53–54. , A. Ebina, S. Nishimura, A. Tsutsumi, O. Hasegawa, S. Tokura, Int. J. cromol. 8 (1986) 311–317. rin, N. Nishi, S. Tokura, J. Naguchi, Polym. J. 11 (1979) 391–395. N. Nishi, T. Komai, S. Tokura, O. Somorin, Polym. J. 13 (1981) 241–245. , H. Ohnuma, S. Nishimura, O. Somorin, S. Tokura, Polym. J. 14 (1982) . , J. Noguchi, S. Tokura, J. Noguchi, Polym. J. 11 (1979) 27–32. , N.M. Rodriguez, V.M. Ramos, E. Agullo, Carbohydr. Polym. 44 (2001) en, I.F. Uchegbu, A.G. Schätzlein, J. Pharm. Pharmacol. 52 (2000) . mos, N.M. Rodriguez, M.S. Rodriguez, A. Heras, E. Agullo, Carbohydr. 1 (2003) 425–429. os, M.S. Rodríguez, E. Agulló, N.M. Rodríguez, A. Heras, Int. J. Polym. 1 (2002) 711–720. mar, R.L. Reis, J.F. Mano, J. Bioact. Compat. Polym. 21 (2006) 327–340. hmann,D.Knittel, E. Schollmeyer, J. Inclus. Phenom.Macrocycl. Chem. ) 169–172. on, M.E. Brewster, J. Pharm. Sci. 85 (1996) 1017–1025. , C.A. Sarguet, A. Gadelle, J. Defaye, B. Perly, D.F. Pilard, J. Chem. Soc., rans. 2 (1995) 1479–1485. a, J. Inclus. Phenom. Macrocycl. Chem. 44 (2002) 3–7. blo, J.R. Isasi, G.G. Gaitano, J. Photochem. Photobiol. A: Chem. 173 48–257. , S. Michaleas, E.A. Vyza, J. Chromatogr. A 1087 (2005) 86–94. , Cyclodextrin Technology, Kluwer Academic, London, 1988, p. 167. y, M. Rinaudo, Macromol. Biosci. 3 (2003) 562–565. haran, J.F. Mano, Carbohydr. Polym. 63 (2006) 153–166. aki, Y. Ueno, N. Sakairi, N. Nishi, S. Tokura, Carbohydr. Polym. 29 (1996) , T. Tojima, S.M. Han, N. Nishi, S. Tokura, N. Sakairi, et al., Polymer 39 261–5263. a, H. Katsura, M. Nishiki, N. Nishi, S. Tokura, N. Sakairi, Carbohydr. 0 (1999) 17–22. , V. Sarguet, C.A. Gadelle, A. Defaye, J.B. Perly, D.F. Pilard, J. Chem. Soc., rans. 2 (1995) 1479. , Y. Wang, Y. Yi, J. Appl. Polym. Sci. 94 (2004) 860–864. [81] C. [82] M 18 [83] A. [84] A. [85] A. [86] H. [87] G. [88] N. 79 [89] A. [90] J. Z [91] C. Bi [92] M [93] J.W 15 [94] C. (2 [95] T.M [96] I.Y (2 [97] H. 26 [98] S.B 26 [99] M 18 [100] M [101] C. [102] C. 34 [103] M Ch [104] F.M M [105] S.J 27 [106] J.R [107] M [108] H. Ju [109] M (2 [110] H. [111] K. [112] S.G 15 [113] H. (1 [114] A. Re [115] W [116] Y.H [117] Y. Bi [118] Y.H 13 [119] P. [120] J.M Co [121] P.P [122] M [123] A. [124] C. be [125] N. (2 [126] S.S 97 [127] K. 81 [128] F. [129] Z. 10 [130] M Re [131] E. [132] M Ni [133] H. Ka , A.B. Schnurch, Biomaterials 22 (2001) 2345–2352. of, C.E. Kast, A.B. Schnurch, Eur. J. Pharm. Biopharm. 55 (2003) . nurch, U.M. Brandt, A.E. Clausen, Sci. Pharm. 67 (1999) 196–208. nurch, M. Hornof, M. Zoidl, Int. J. Pharm. 260 (2003) 229–237. sen, C.E. Kast, A.B. Schnurch, Pharm. Res. 19 (2002) 602–608. ild, Prog. Polym. Sci. 17 (1992) 163–249. s, D. Hourdet, Polymer 42 (2001) 6329–6337. ta, N. Tasumoto, T. Sano, Y. Matsukawa, J. Appl. Polym. Sci. 80 (2001) . man, N.A. Peppas, J. Biomater. Sci. Polym. Ed. 10 (1999) 999–1009. , N.A. Peppas, J. Biomater. Sci. Polym. Ed. 13 (2002) 511–525. he, W.A. Monal, N. Davidenko, R. Sastre, A. Gallardo, J. San Roman, rials 20 (1999) 1869–1878. haran, J.F. Mano, Macromol. Biosci. 6 (2006) 991–1008. , M.C. Jung, H.D. Park, K.D. Park, G.W. Ryu, J. Biomater. Sci. Polym. Ed. ) 1065–1079. C.J. Wen, C.L. Lin, W.Y. Chiu, J. Polym. Sci. Part A: Polym. Chem. 42 029–3037. , H.R. Chen, Carbohydr. Polym. 61 (2005) 334–347. S.J. Kim, M.S. Shin, Y.M. Lee, D.I. Shin, S.I. Kim, J. Appl. Polym. Sci. 85 661–2666. .P. Zhang, P.C. Sun, B.L. He, X.X. Zhu, Radiat. Phys. Chem. 74 (2005) , D.I. Ha, S.K. Cho, S.J. Kim, Y.M. Lee, J. Appl. Polym. Sci. 92 (2004) 20. ng, J. Zhu, F.W. Harris, P. Li, Macromol. Rapid Commun. 25 (2004) 23. ng, J. Zhu, F.W. Harris, P. Li, Macromol. Symp. 226 (2005) 177–185. W.Y. Chiu, C.F. Lee, J. Colloid Interf. Sci. 290 (2005) 397–405. et, R. Auzély-Velty, M. Rinaudo, L’actualité chimique 294 (2006) g, J. Qiang, Y. Fang, D. Hu, Y. Cui, X. Fu, J. Polym. Sci. Part A: Polym. 8 (1999) 474–481. coolea,A.Heras, I. Aranaz,G.Galed,M.E. Fernandez-Valle,W.A.Monal, ol. Biosci. 3 (2003) 612–619. S.R. Shin, S.M. Lee, I.Y. Kim, S.I. Kim, J. Appl. Polym. Sci. 88 (88) (2003) 24. ma, D.R. Rohindra, A.V. Nand, Polym. Bull. 54 (2005) 195–204. g, Y. Fang, D. Hu, React. Funct. Polym. 48 (2001) 215–221. ben, B.J.D. Leeuw, B.W. Langemeyer, A.G.D. Boer, J.C. Verhoef, H.E. r, Pharm. Res. 13 (1996) 1668–1672. ou, T. Nihot, M. Jansen, J.C. Verhoef, H.E. Junginger, J. Pharm. Sci. 90 8–46. g, X.Y. Ding, H. Ge, Y. Yuan, C. Yang, Biomaterials 23 (2002) 3193–3201. tha, U. Bala, K.P. Rao, Eur. Polym. J. 31 (1995) 377–382. bar, K.S. Soppimath, T.M. Aminabhavi, J. Appl. Polym. Sci. 87 (2003) 36. oka, K. Nonaka, K. Fukuda, S. Kazama, Biosci. Biotechnol. Biochem. 59 901–1904. , A. Ishibe,M.Nakano, T. Yamahira, S. Itai, S. Jinno,H. Kawahara, Pharm. 1998) 1844–1850. , K.D. Yao, Q.G. Liu, J. Appl. Polym. Sci. 82 (2001) 3391–3395. , S.H. Kim, C.R. Park, Bioconj. Chem. 12 (2001) 932–938. , J. Chen, Y. Zhang, Y. Pan, J. Zhao, L. Ren, et al., Biotechnol. Appl. . 46 (2007) 197–204. , H. Jiang, R. Chan, W. Chen, J. Biomater. Sci. Polym. Ed. 16 (2005) 78. M. Kurisawa, J.E. Chung, Y.Y. Yang, Biomaterials 28 (2007) 540–549. eira, N. Kotobuki, A.P. Marques, R.P. Pirraco, J. Benesch, M. Hirose, S.A. . Mano, H. Ohgushi, R.L. Reis, Adv. Funct. Mater. 18 (2008) 1840–1853. , Y.S. Ya, K.J. Hong, T. Kajiuchi, Carbohydr. Polym. 53 (2003) 305–310. haran, J.F. Mano, Macromol. Biosci. 5 (2005) 965–973. uland, M.J. Alonso, Int. J. Pharm. 340 (2007) 134–142. nzo, A. Concheiro, A.S. Dubovik, N.V. Grinberg, T.V. Burova, V.Y. Grin- ontrol. Rel. 102 (2005) 629–641. arai, H.R. Ramay, J. Gunn, F.A. Matsen, M. Zhang, J. Control. Rel. 103 09–624. W. Liu, N. Cheng, B. Zhang, Z.Z. Cao, K.K. Yao, Bioconj. Chem. 16 (2005) . koglu, C.M. Alves, J.F. Mano, R.L. Reis, Macromol. Biosci. 4 (2004) . . Chen, H. Wang, H. Liu, K. Yao, P. Sun, Polymer 44 (2003) 6435–6441. J. Chen, S. Gao, J. Chang, J. Zhang, E.T. Kang, Biomaterials 25 (2004) 67. haran, M.A. Rodriguez-Perez, J.A. de Saja, J.F. Mano, J. Biomed. Mater. t B: Appl. Biomater. 81B (2007) 427–434. . Frick, U. Losert, A.B. Schnurch, Int. J. Pharm. 256 (2003) 183–189. calo, Y. Yokogawa, M. Toriyama, T. Suzuki, Y. Kawamoto, F. Nagata, K. a, J. Mater. Sci. Mater. Med. 6 (1995) 409–419. ma, Y. Yokogawa, F. Espinosa, Y. Kawamoto, K. Nishizawa, F. Nagata, T. ma, Biomaterials 20 (1999) 879–884. 414 N.M. Alves, J.F. Mano / International Journal of Biological Macromolecules 43 (2008) 401–414 [134] X. Wang, J. Ma, Y. Wang, B. He, Biomaterials 22 (2001) 2247–2255. [135] X. Wang, J. Ma, Y. Wang, B. He, Biomaterials 23 (2002) 4167–4176. [136] C.I. Dias, J.F. Mano, N.M. Alves, J. Mater. Chem. 18 (2008) 2493–2499. [137] T.H. Kim, J.W. Nah, M.H. Cho, T.G. Park, C.S. Cho, J. Nanosci. Nanotechnol. 6 (2006) 2796–2803. [138] E.S. Gil, S.M. Hudson, Prog. Polym. Sci. 29 (2004) 1173–1222. [139] J.H. Cho, S.H. Kim, K.D. Park, M.C. Jung, W.I. Yang, S.W. Han, Biomaterials 25 (2004) 5743–5751. [140] C. Valanta, B. Christen, A. Bernkop-Schnurch, J. Pharm. Pharmacol. 50 (1998) 445–452. [141] R.A.A. Muzzarelli, G. Skjak-Braek, T. Anthonsen, P. Sandford, Appl. Polym. Sci. (1989) 87–99 (Elsevier, London). [142] X.F. Liu, Y.L. Guan, D.Z. Yang, Z. Li, K.D. Yao, J. Appl. Polym. Sci. 79 (2001) 1324–1335. [143] S.G. Hu, C.H. Jou, M.C. Yang, J. Appl. Polym. Sci. 88 (2003) 2797–2803. [144] C. Mao, W.B. Zhao, A.P. Zhu, J. Shen, S.C. Lin, Process. Biochem. 39 (2004) 1151–1157. [145] T.W. Chung, Y.F. Lu, S.S. Wang, Y.S. Lin, S.H. Chu, Biomaterials 23 (2002) 4803–4809. [146] Y. Li, L. Liu, F. Fang, Polym. Int. 52 (2003) 285–290. [147] R.A.A. Muzzarelli, F. Tanfani, M. Emanuelli, Biotechnol. Bioeng. 27 (1985) 1151–1157. [148] I. Saucedo, E. Guibal, C. Roulph, P. Le Cloirec, Environ. Technol. 13 (1992) 1101–1116. [149] Y. Shigemasa, H. Usui, M. Morimoto, H. Saimoto, Y. Okamoto, S. Minami, Car- bohydr. Polym. 39 (1999) 237–243. [150] E. Guibal, T. Vincent, R. Navarro Mendoza, J. Appl. Polym. Sci. 75 (2000) 119–134. [151] G. Cardenas, P. Orlando, T. Edelio, Int. J. Biol. Macromol. 28 (2001) 167–174. [152] E. Guibal, N.V.O. Sweeney, T. Vincent, J.M. Tobin, React. Funct. Polym. 50 (2002) 149–163. [153] K. Kondo, S. Nakagawa,M.Matsumoto, T. Yamashita, I. Furukawa, J. Chem. Eng. 30 (1997) 846–852. [154] E.O. Dingilian, G.E. Heinsohn, PCT Int. Appl. 117 (1992) 153112 (WO 9208742. CA). [155] T. Mori, C. Mori, Y. Nishiyama, K. Kurita, Kichin Kitosan Kenkyu 5 (1999) 168–169. [156] N.Nishi, Y.Maekita, S.Nishimura,O.Hasegawa, S. Tokura, Int. J. Biol.Macromol. 9 (1987) 109–114. [157] G. Schwarzenbach, H. Ackermann, P. Ruckstuhl, Helv. Chim. Acta 32 (1949) 1175–1186. [158] G. Paradossi, F. Cavalieri, V. Crescenzi, Carbohydr. Res. 300 (1997) 77–84. [159] G. Paradossi, E. Chiessi, F. Cavalieri,D.Moscone,V.Crescenzi, Polym.GelsNetw. 5 (1997) 525–540. [160] M.D. Cathell, J.C. Szewczyk, F.A. Bui, C.A. Weber, J.D. Wolever, J. Kang, C.L. Schauer, Biomacromolecules 9 (2008) 289–295. [161] R. Qu, C. Sun, C. Ji, C. Wang, H. Chen, Y. Niu, C. Liang, Q. Song, Carbohydr. Res. 343 (2008) 267–273. [162] C. Peng, Y. Wang, Y. Tang, J. Appl. Polym. Sci. 70 (1998) 501–506. [163] S. Tan, Y. Wang, C. Peng, Y. Tang, J. Appl. Polym. Sci. 71 (1999) 2069–2074. [164] Z. Yang, Y. Wang, Y. Tang, J. Appl. Polym. Sci. 74 (1999) 3053–3058. [165] Z. Yang, J. Li, J. Appl. Polym. Sci. 86 (2002) 2677–2681. [166] B. Martel, M. Devassine, G. Crini, M. Weltrowski, M. Bourdonnaeu, M. Morcel- let, J. Polym. Sci. Part A: Polym. Chem. Ed. 39 (2001) 169–176. [167] G. Crini, P.M. Badot, Prog. Polym. Sci. 33 (2008) 399–447. [168] A.C. Chao, S.S. Shyu, Y.C. Lin, F.L. Mi, Bioresour. Technol. 91 (2004) 157–162. [169] G. Crini, B. Martel, G. Torri, Int. J. Environ. Pollut. 33 (2008). [170] K. Sreenivasan, J. Appl. Polym. Sci. 69 (1998) 1051–1055. Chitosan derivatives obtained by chemical modifications for biomedical and environmental applications Introduction Graft copolymerization Grafting initiated by free radicals Grafting using radiation Enzymatic grafting Cationic graft polymerization Special cases of chitin and chitosan modifications Phosphorylated chitin and chitosan Combination of chitosan derivatives with cyclodextrins Thiol-containing chitosan "Smart chitosan": example of new chitosan-based hydrogels exhibiting temperature-responsive behaviour Graft copolymerized hydrogels Chemically crosslinked blends Applications for modified chitosan materials Drug delivery Tissue engineering Antimicrobial agents and other biomedical applications Adsorption of metal ions Dye removal Conclusions References