Natural polymers chitosan

Kumar, G., Bristow, J.F., Smith, P.J., and Payne, G.R 2000. Enzymatic gelation of the natural polymer chitosan. Polymer, 41 2157-2168. 

The natural polymer chitosan possesses the intrinsic advantages of being used as a delivery vehicle. Chitosan and its derivahves can be processed under mild conditions therefore, growth factor inachvation due to otherwise harsh processing conditions can be avoided. In addition, chitosan can be fabricated into different forms and shapes to incorporate growth factors and other biomolecules for various in vivo applications. 

However, being a natural polymer, chitosan has aU disadvantages of natural materials mentioned earlier (see Section 11. A). Presently, a lot of other polyplexes based on cationic synthetic polymers have been described in the literature. Among others, we could mention rather new DNA delivery nanoparticles based on poly(2-dimethylamino)ethyl methacrylate-co-poly(ethylene glycol) (PDMAEMA) [70,71] and PEGylated polyethylenimine (PEI/DNA) [72]. The last polyplexes have been encapsulated in PLGA microparticles and proposed for mucosal (oral) polyplex-based vaccination of Wistar rats. 

For veterinary drug delivery systems, additional requirements exist in regard to safety when compared with delivery systems for human. Besides the safety of the target animal, consumer safety is also important. Particularly for food-producing animals, because these animals enter the food chain, tissue residues must be addressed for both the drug and the polymer. Environmental safety should also not be affected. In view of these requirements, being a nontoxic, nonallergenic, biocompatible natural polymer, chitosan can be considered as a safe polymer for veterinary applications. 

In this chapter, we discussed possible methods for the formation of electrically conducting biocomposites using proteinaceous sohd biomasses arising from leather industries as wastes. The proteinaceous collagen wastes were blended with natural polymers (chitosan or GG) and different fillers such as GrC and nanotubes (ie, BCNTs and FWCNTs) to form hybrid-conducting biocomposite films. The formed biocomposife films were found fo exhibit promising mechanical, thermal, and electrical properties. The thermal properties of both of the hybrid composite materials increase moderately with the increase in the addition of nanocarbons. The mechanical... 

Among the natural polymers, chitosan occupies a special position due to its abundance, versatility, facile modification, and unique properties, including biodegradability (Kean Thanou, 2010), biocompatibility (Costa-Pinto et al., 2014 Hsu... 

Polyamizine, which can be obtained by modifying the copolymer of N-vinyl formamide and acrylonitrile by an acid or alkali, has also been used in recent years [5]. This polymer has high molecular weight and high concentration of cations. A natural polymer, chitosan is used as a cationic polymer. Chitosan is obtained by acetylating chitin, which is contained in the shells of crabs and shrimps. 

In particular the natural polymer chitosan has emerged as a promising material for biological functionalization and improvement of specific biorecognition in MEMS and lab-on-a-chip device, since it is biocompatible and biodegradable, has unique chemical properties, and is easily deposited in thin-fihns (Koev et al., 2010 Yi et al., 2005 Wu et al., 2003). Chitosan has been reported for fabrication of nanowire and nanodot chitosan structures (Park et al., 2007), as well as films with controlled thickness (Zangmeister et al., 2006) and a variety of microscale... 

Associations can be of physical nature too. Chitosan blends with hydrophilic polymers including polyvinylalcohol, polyethyleneoxide and poly-vinylpyrrohdone, were investigated as candidates for oral gingival delivery systems. Chitosan blends were superior to chitosan alone in terms of comfort, ease of processing, film quality, and flexibihty [325]. 

Many years ago chitin was seen as a scarcely appeahng natural polymer due to the variety of origins, isolation treatments and impurities, but the works of several analytical chemists and the endeavor of an increasing number of companies have qualified chitins and chitosans for sophisticated applications in the biosciences. Chemistry today offers a range of finely characterized modified chitosans for use in the biomedical sciences. Moreover, surprising roles of these polysaccharides and related enzymes are being unexpectedly discovered [351]. 

Several examples have been described in which a chiral natural polymer, such as silk fibroin or chitosan, act as chiral ligand and support at the same time. In such cases, the chiral ligand (the monomer or monomers coordinating... 

Besides the previously mentioned collagen, a wide variety of natural polymers have been involved in the synthesis of bio-nanohybrid materials with potential application in bone repair and dental prostheses. For instance, some recent examples refer to bionanocomposites based on the combination of HAP with alginate [96,97], chitosan [98,99], bovine serum albumin (BSA) [100], sodium caseinate [101], hyaluronic acid [102], silk fibroin [103,104], silk sericin [105], or polylactic add (PLA) [106,107]. These examples illustrate the increasing interest in the subject of HAP-based biohybrid materials, which has led to almost 400 articles appeared in scientific journals in 2006 alone. 

Gupta V., Agarwal J., Sharma S. Adsorption Analysis of Mn(VII) from Aqueous Medium by Natural Polymer Chitin and Chitosan, Asian J. of Chem., 20(8), 6195-98 (2008)... 

The selective dense layer of hydrophilic membranes is made from different polymers with a high affinity for water. These polymers contain ions, oxygen functions like hydroxyl, ester, ether or carboxylic moieties, or nitrogen as imino or imi-do groups. Preferred hydropilic polymers are polyvinylalcohol (PVA) [32], poly-imides, cellulose acetate (CA) or natural polymers like chitosan [33] or alginates. Organophilic membranes usually consist of crosslinked silicones, mostly polydimethyl siloxane (PDMS) or polymethyl octyl siloxane (POMS). 

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. 

Biodegradable polymers, both synthetic and natural, have gained more attention as carriers because of their biocompatibility and biodegradability and therewith the low impact on the environment. Examples of biodegradable polymers are synthetic polymers, such as polyesters, poly(orfho-esters), polyanhydrides and polyphosphazenes, and natural polymers, like polysaccharides such as chitosan, hyaluronic acid and alginates. 

Chitosan is a polymer produced from hydrolysis of natural chitin. Chitosan is not readily soluble in aqueous solutions, but can be solubilized and is thus considered with other water soluble polymers. In the hydrophobic form, chitosan has been treated in a similar manner to other hydrophobic polymers with microparticles produced by emulsion and phase separation techniques. Microparticles can be taken up by the gastrointestinal lining in a manner similar to that discussed for other hydrophobic microparticles. 

Lehr, C.M., et al. n vitro evaluation of mucoadhesive properties of chitosan and some other natural polymers,Int. J. Pharm., 78, 43, 1992. 

Abstract Carbohydrates have been investigated and developed as delivery vehicles for shuttling nucleic acids into cells. In this review, we present the state of the art in carbohydrate-based polymeric vehicles for nucleic acid delivery, with the focus on the recent successes in preclinical models, both in vitro and in vivo. Polymeric scaffolds based on the natural polysaccharides chitosan, hyaluronan, pullulan, dextran, and schizophyllan each have unique properties and potential for modification, and these results are discussed with the focus on facile synthetic routes and favorable performance in biological systems. Many of these carbohydrates have been used to develop alternative types of biomaterials for nucleic acid delivery to typical polyplexes, and these novel materials are discussed. Also presented are polymeric vehicles that incorporate copolymerized carbohydrates into polymer backbones based on polyethylenimine and polylysine and their effect on transfection and biocompatibility. Unique scaffolds, such as clusters and polymers based on cyclodextrin (CD), are also discussed, with the focus on recent successes in vivo and in the clinic. These results are presented with the emphasis on the role of carbohydrate and charge on transfection. Use of carbohydrates as molecular recognition ligands for cell-type specific dehvery is also briefly... 

Natural polymers polysaccharides (celullose, starch, pectins, dextrans, agar, agarose, alginate, chitine, chitosan, etc.) and fibrous proteins (collagen, keratine, etc.). 

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