Polymeric chitosan

Dufes, C., J. M. Muller, W. Couet, J. C. Olivier, I. F. Uchegbu, and A. G. Schatzlein. 2004. Anticancer drug delivery with transferrin targeted polymeric chitosan vesicles. Pharm Res 21(l) 101-7. 

Fig. 8 Force normalized by radius as a function of surface separation. The forces were measured between muscovite mica surfaces across a 0.1 mM KBr solution containing 50 ppm chitosan-E045 oligomers. Filled and unfilled symbols represent forces measured on approach and on separation, respectively. The forces measured between mica surfaces coated with polymeric chitosan are represented by crosses. The arrows represent inward jumps due to the action of an attractive force...

Dufes C, Schatzlein AG, Tetley L, et al. Niosomes and polymeric chitosan based vesicles bearing transferrin and glucose ligands for drug targeting. Pharm Res 2000 17 1250-1258. 

An alternative to the experiments just described is the esterification of chitosan with the use of lactide or polylactide for example, Skotak et al. [59] prepared chitosan derivatives following a one pot approach by grafting L-lactide oligomers via ring-opening polymerization. Chitosan (600 mg) was dissolved in 10 mL of... 

I. F. Uchegbu et ah. Polymeric chitosan-based vesicles for drug delivery. /. Pharm. Pharmacol., 50(5) 453-8 (1998). 

Hu (2003) Ozone Acrylic acid polymerization chitosan attachment Antibacterial activity [43]... 

A cobalt(II)-chitosan chelate has been prepared by soaking a chitosan film in C0CI2 aqueous solution. The chitosan chelated Co(II) through both oxygen and nitrogen atoms in the chitosan chain. The tetracoordinated, high-spin Co(II)-chitosan chelate could be used as a catalyst, and the polymerization of vinyl acetate was carried out in the presence of Na2S03 and water at pH 7 and normal temperature. The polyvinyl acetate possessed a random structure [114,115]. 

The semi-interpenetrating polymeric networks obtained by the radical-induced polymerization of N-isopropylacrylamide in the presence of chitosan using tetraethyleneglycoldiacrylate as the cross-linker were used as controlled release vehicles for pilocarpine hydrochloride [294]. 

Another polysaccharide system that has received considerable interest is the chitosans which are water soluble derivatives of chitin. These materials appear to be very biocompatible and degradable and so are potentially excellent candidates as polymeric drug systems (27). 

J. Zhang, L. Wang, A. Wang, Preparation and properties of chitosan-g-poly(acrylic acid)/montmorillonite superabsorbent nanocomposite via In situ intercalative polymerization, Ind. Eng. Chem Res., vol. 46, pp. 2497-2505, 2007. 

With the development of enzymatic polymerization in solution, also first accounts for SIP appeared. Loos et al. [350] reported on enzymatic surface polymerization of glucose-l-phosphate with potato phosphorylase as the catalyst resulting in oligo- or poly-(a,l- 4)-D-glucopyranose. As initiator sites, immobilized malto-heptaose was used. Enzymatic grafting of hexyloxyphenol onto chitosan is reported by Payne and coworkers [351]. 

Depolymerization of some natural polymers is another typical example. Milling of chitin or chitosan, at ambient temperature, leads to cleavage of the cellulose polymeric chain. Scission of 1,4-glucosidic bonds takes place, and the radicals formed recombine. Based on electron spin resonance, Sasai et al. (2004) monitored both the homolysis and the radical recombination. The recombination led to the formation of midsize polymeric chains only. Some balance was established between the homolytic depolymerization and the size-limited recombination of the radicals primarily formed. 

Chitosan (Fig. 16) is an amino-modified natural polysaccharide that canbe also used as a polymeric gel for the covalent binding of OND probes [61]. Chitosan offers several advantages for NA immobilization. Its pH responsive properties allow it to be easily immobilized onto glass slides for the construction of arrays. Specifically, chitosan is soluble at low pH, when its amine groups are protonated, but becomes insoluble when the pH is raised above its pKa 6.3). 

To work with a homogeneous series of chitosans with the same distribution of degrees of polymerization but different DAs, a starting sample of chitosan of DA 5.2% was reacetylated. Acetylation was performed with Acetic Anhydride in a hydroalcoholic medium. Characteristics of the various prepared chitosan samples are given in table 1. (Adapted from Montembault et ah, 2005)... 

Yang, L., Chen, L., Zeng, R., Li, C, Qiao, R., Hu, L., and Li, Z. (2010). Synthesis, nanosizing and in vitro drug release of a novel anti-HIV polymeric prodrug Chitosan-O-isopropyl-50-O-d4T monophosphate conjugate. Bioorg. Med. Chem. 18,117-123. 

Chiral induction was observed in the cyclopolymerization of optically active dimethacrylate monomer 42 [88], Free-radical polymerization of 42 proceeds via a cycliza-tion mechanism, and the resulting polymer can be converted to PMMA. The PMMA exhibits optical activity ([ct]405 -4.3°) and the tacticity of the polymer (mm/mr/rr =12/49 / 39) is different from that of free-radical polymerization products of MMA. Free-radical polymerization of vinyl ethers with a chiral binaphthyl structure also involved chiral induction [91,92]. Optically active PMMA was also synthesized through the polymerization of methacrylic acid complexed with chitosan and conversion of the resulting polymer into methyl ester [93,94]. 

Therefore, the enhancement of transport is not accompanied by damage to the cells, which is superior to the absorption-enhancing effects of other small molecules, which lead to irreversible changes in the cell membrane and damage to the cell. Thus, much attention has been paid to chitosan as a polymeric substance that enhances GI absorption. 

---