Abstract
In the field of gene therapy, chitosan (CS) gained interest for its promise as a non-viral DNA vector. However, commercial sources of CS lack precise characterization and do not generally reach sufficient solubility in aqueous media for in vitro and in vivo evaluation. As low molecular weight CS showed improved solubility, we investigated the process of CS depolymerization by acidic hydrolysis, using either long time heating at 80 °C or short time microwave-enhanced heating. The resulting depolymerized chitosan (dCS) were analyzed by gel permeation chromatography (GPC) and 1H nuclear magnetic resonance (NMR) to determine their average molecular weight (Mn, Mp and Mw), polydispersity index (PD) and degree of deacetylation (DD). We emphasized the production of water-soluble CS (solubility > 5 mg/mL), obtained in reproducible yield and characteristics, and suitable for downstream functionalization. Optimal microwave-assisted conditions provided dCS with a molecular weight (MW) = 12.6 ± 0.6 kDa, PD = 1.41 ± 0.05 and DD = 85%. While almost never discussed in the literature, we observed the partial post-production aggregation of dCS when exposed to phase changes (from liquid to solid). Repeated cycles of freezing/thawing allowed the selection of dCS fractions which were exempt of crystalline particles formation upon solubilization from frozen samples.
Highlights
Chitosan (CS) is a natural biopolymer composed of glucosamine and N-acetylglucosamine units, that gained the interest of scientists over the last four decades for its promises in pharmaceutics and medicine [1]
In view of further functionalization and improved bioavailability in the physiological medium, this study focused on the characterization of the soluble fraction of depolymerized chitosan (dCS)
Both commercial CS sources led to similar yields of depolymerization (Table 1, entries 3,4)
Summary
Chitosan (CS) is a natural biopolymer composed of glucosamine and N-acetylglucosamine units, that gained the interest of scientists over the last four decades for its promises in pharmaceutics and medicine [1] This polymer is produced on a commercial scale by the deacetylation of chitin, which is widely present in crustacea’s shells and fungi. CS exhibits high biocompatibility as well as favorable adsorption properties and biodegradability [3,4], which make it a versatile biomaterial for the development of biomedical and pharmaceutical products [5]. Biomaterials based on CS display promising anti-bacterial and anti-oxidant properties that led to the development of dressing for wound healing [6]. Other applications use CS gels for drug-delivery systems and scaffold for bone treatment and biomedical imaging [3,7,8]
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