Chitosan, derivatives complex

Changes in the backbone of the sulfonic acid azo dyes often produce drastic changes in properties of the materials. The disulfonic acid (5) is somewhat similar to (3), but is used to color leather red (77). More esoteric dyes have also been developed based on sulfonic acid metal complexes and chitosan-derived materials (78,79). 

In fact, one of the major applications of chitosan and some of its many derivatives is based on its ability to bind precious, heavy and toxic metal ions. Another article reviews the various classes of chitosan derivatives and compares their ion-binding abihties under varying conditions, as well as the analytical methods to analyze them, the sorption mechanism, and structural analysis of the metal complexes. Data are also presented exhaustively in tabular form with reference to each individual metal ion and the types of compounds that complex with it under various conditions, to help reach conclusions regarding the comparative efficacy of various classes of compounds [112]. 

The complexing of chitosan and its basic derivatives with anionic substances is paralleled by compatibility with cationic and nonionic compounds. Similarly, the anionic derivatives of chitosan show complex formation with cationic agents and are compatible with anionic and nonionic compounds. The capability of these chitosan derivatives to complex with certain metal ions, notably those of the transition series, is also important, having possibilities for the removal of metal salts from effluent. The hierarchy in terms of binding capacity is Cr(III) < Cr(II) < Pb(II) < Mn(II) < Cd(II) < Ni(II) < Fe(II) < Co(II). 

Chitin and chitosan derivatives have also been studied as blood compatible materials both in vivo and in vitro [520], Anticoagulant activity was greatest with O sulfated N acetyl chitosan, followed by N,0 sulfated chitosan, heparin, and finally sulfated N acetyl chitosan. The lipolytic activity was greatest for N,0 sulfated chitosan followed by heparin. The generally poor performance of chitosan was attributed to polyelectrolyte complexes with free amino groups present on the membrane surface. The O sulfate or acidic group at the 6 position in the hexosamine moiety was identified as the main active site for anticoagulant activity. 

Owing to its free amine functions, chitosan may also be protonated (pfCa = 5.6). In in vitro studies with Hela-cells, chi-tosan/DNA complexes showed a gene-transfection potency similar to that reported for PEI/DNA complexes. Plain chitosan, however, is almost insoluble in water at neutral pH (but soluble at acidic pH), for this reason, trimethylated, quaternary chitosan derivatives have been produced that are sufficiently soluble under physiological conditions and easily complex DNA molecules. In in vitro experiments with COS-1 and CaCo-2 cells, these innovative chitosan derivatives proved superior to nontreated chitosan polymers, particularly as they showed no unspecific cytotoxicity [87]. 

Renbutsu, E., M. Okamura, T. Tsuka, Y. Okamoto, Y. Omura, and S. Minami. 2007. Clinical application of UV-curable chitosan derivative and synthetic resin complex to prevent postoperative pneumothorax in a fehne diaphragmatic hernia. In Advances in Chitin Science Vol. X, K. M. Varum, S. enel, M. M. umnu, and A. A. Hmcal (eds.), Alp Ofset, Ankara, Turkey, pp. 413-416. 

Chitin/calcium phosphate complexes can form the basis of artificial bone and dental materials [40] and phosphated chitosan derivatives have been patented as detergent builders [41]. A protonconducting biopolymer has been obtained from chitin phosphate and imidazole [42]. 

Various derivatives have been explored in various studies e.g. in one study three types of cross-linked chitosan polymers were investigated for their adsorption capability for multiple mycotoxins, including allatoxin Bj (AFB,), ochratoxin A (OTA), zearalenone (ZEN), fumonisin B,(FB,), deoxynivalenol (DON) andT-2 toxin (T2). Among these synthetic adsorbents, cross-linked chitosan-glutaraldehyde complex presented the highest adsorption capability for aflatoxin B, (73 %), ochratoxin A... 

Sajomsang W, Ruktanonchai U, Gonil P, Mayen V, Opanasopit P. Methylated N-aryl chitosan derivative/DNA complex nanoparticles for gene delivery Synthesis and structure-activity relationships. Carbohydr Polym. 2009 78(4) 743-52. 

A new chitosan derivative was synthesized by the chemical modification of chitosan (CTS) with vaiullin-based complexing agent namely 4-hydroxy-3-methoxy-5-[(4-... 

Emara, A. A. A., Tawab, M. A., El-ghamry, M.A., and Elsabee Maher, Z. (2011). Metal uptake by chitosan derivatives and structure studies of the polymer metal complexes. Carbohyd Polym. 83(1), 192-202. 

Krishnapriya, K. R. and Kandaswamy, M. (2009). Synthesis and eharaeterization of a cross-linked chitosan derivative with a complexing agent and its adsorption studies toward metal (II) ions. Carbohydrate Research 344, 1632-1638. 

Tang, L. G. and Hon, D. N. S. (2001). Chelation of chitosan derivatives with zinc ions.llI.Asso-ciation complexes of Zn on to O, A-carboxy methyl chitosan. Journal of Applied Polymer Science 1% 2 1476-1485. 

In a study conducted by Liu et at, a doxorubicin (Dox)-carrier system was developed by electrostatic complexion of G4 PAMAM dendrimer with a pH-sensitive diblock copolymer of poly(methacryloyl sulfadimethoxine) (PSD) and PEG, with lactose (LA) coupled at the distal end of the PEG chain [77]. A higher cumulative Dox release from LA-PEG-b-PSD/PAMAM complexes was observed at pH 6.5 compared to pH 7. In another study, a pH-sensitive dendrimer nanoparticle was prepared, where surface cationic charge of the PAMAM dendrimer was reduced to prevent opsonization in the systemic circulation [78]. Zwitterionic chitosan (ZWC), a chitosan derivative with a unique pH-sensitive charge profile, was used to modify the cationic surface of PAMAM dendrimers. A stable electrostatic complex between ZWC and PAMAM was formed at pH 7.4, where the PAMAM dendrimer surface was covered with ZWC. The results demonstrated that ZWC can mask the surface charge, which minimizes hemolytic and cytotoxic activities of PAMAM dendrimers. However, the complex dissociated due to the charge conversion at low pH, allowing PAMAM dendrimer charge to be exposed and facilitate its entrance into the cells. 

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