Chitosan: some pharmaceutical and biological aspects - an update

Abstract

Chitosan, a natural polysaccharide, is being widely used as a pharmaceutical excipient. It is obtained by the partial deacetylation of chitin, the second most abundant natural polymer.Chitosan comprises a series of polymers varying in their degree of deacetylation, molecular weight, viscosity, pKa etc. The presence of a number of amino groups permit chitosan to chemically react with anionic systems, thereby resulting in alteration of physicochemical characteristics of such combinations.Chitosan has found wide applicability in conventional pharmaceutical devices as a potential formulation excipient, some of which include binding, disintegrating and tablet coating properties. The polymer has also been investigated as a potential adjuvant for swellable controlled drug delivery systems. Use of chitosan in novel drug delivery as mucoadhesive, gene and peptide drug administration via the oral route as well as its absorption enhancing effects have been explored by a number of researchers.Chitosan exhibits myriad biological actions, namely hypocholesterolemic, antimicrobial and wound healing properties. Low toxicity coupled with wide applicability makes it a promising candidate not only for the purpose of drug delivery for a host of drug moieties (antiinflammatories, peptides etc.) but also as a biologically active agent.It is the endeavour of the present review to provide an insight into the biological and pharmaceutical profile of chitosan. Various investigations carried out recently are reported, although references to research performed on chitosan prior to the recent reviews have also been included, where appropriate.

Covalent immobilization of antimicrobial peptides (AMPs) onto biomaterial surfaces

“…Non-fouling surfaces combine one or more approaches in order to influence the amount and/or conformation of adsorbed proteins, preventing bacterial adhesion and biofilm formation. Some examples are UV radiation of titanium surfaces to augment wettability [27], use of anti-adherent agents bearing negative charges [28], polymer coatings such as poly(ethylene glycol) (PEG), poly(hydroxyethylmethacrylate) (PHEMA) [18,29], poly(methacrylic acid) [30], polyurethanes [31] or even bioactive polymers such as chitosan, which possess the ability to inhibit bacterial adhesion and/or to kill adherent bacteria [32]. Unfortunately, the effectiveness of non-fouling coatings for reducing bacterial adhesion is limited and varies greatly depending on bacterial species.…”

Síntese e avaliações físico-químicas e biológicas de derivados de quitosana de alta e baixa massa molecular

“…Quando a desacetilação da quitina é superior a 65%-60%, o co-polímero resultante é a quitosana (AZEVEDO et al, 2007;SANTOS;FERREIRA, 2006;SINGLA;CHAWLA, 2001;SHI et al, 2006).…”

“…A quitosana é insolúvel em água em pH alcalino e neutro e solúvel em pH ácido (SINGLA; CHAWLA, 2001;SHI et al, 2006). Em ácidos diluídos (pH<5,5), os grupamentos amino livres são protonados e a molécula se torna solúvel (SHI et al, 2006).…”

“…Por apresentar alta massa molecular e uma estrutura linear, a quitosana em pequenas concentrações (2-3%) confere viscosidade às soluções em meio ácido, e um comportamento pseudoplástico, redução da viscosidade com o aumento da tensão de cisalhamento (SINGLA; CHAWLA, 2001;KUMAR, 2000;HWANG;JUNG;LEE, 2002).…”

“…A quitosana vem sendo aplicada no tratamento de água para remoção de íons, como floculante para clarificação e redução de odores; na agricultura, como adubo e fungicida e no revestimento de frutas e sementes; auxiliar de curtimento e acabamento, aumenta a temperatura do encolhimento, penetração e fixação de corantes e ainda melhora a resistência à água (SINGLA, 2001 Foi também observado que a quantidade de policátions disponíveis para interagir na superfície bacteriana é aparentemente reduzida quando aumenta-se a concentração de quitosana, isso deve-se, possivelmente, ao elevado número de pontos carregados que faz com que as cadeias formem aglomerados devido a agregação de moléculas. Atualmente este mecanismo de ação antibacteriana da quitosana é o mais aceito.…”