Alginate fibres modified with unhydrolysed and hydrolysed chitosans for wound dressings

A range of commercial chitosans were sourced, subjected to controlled acid hydrolysis, and their molecular size profiles and degrees of acetylation (DA) determined (pre- and post-hydrolysis) by High Performance Size Exclusion Chromatography and H-1-NMR spectroscopy, respectively. Unhydrolysed and hydrolysed chitosans were subsequently utilised for modification of sodium alginate/alginic acid fibres (prepared using a range of different fibre spinning conditions), and levels of chitosan incorporated onto/into base alginate fibres were estimated by elemental analysis. Tensile properties (% elongation and tenacity) of resultant chitosan/alginate fibres were determined in order to assess their suitability for potential application in wound dressings. A broad range of chitosan contents (similar to0-6% w/w) and hydrolysed chitosan contents (similar to7-25% w/w) were obtained using a variety of alginate and chitosan starting materials. Modification of fibres with unhydrolysed chitosans generally resulted in a significant reduction in tenacity (and a reduction in % elongation if a water washing stage was not used), i.e. no increase in fibre strength was observed, implying that the unhydrolysed chitosan is more like a coating rather than penetrating/reinforcing the alginate fibre. Reduction of chitosan molecular weight had a positive effect on its ability to penetrate the alginate fibres, not only increasing fibre chitosan content, but also reinforcing fibre structure and thus enhancing tensile properties (compared with unhydrolysed chitosan/alginate fibres). Hydrolysed chitosan/alginate fibres demonstrated an antibacterial effect (in terms of bacterial reduction) with initial use, and had the ability to provide a slow release/leaching of antibacterially active components (presumably hydrolysed chitosan fragments). The overall aims of maximising chitosan content (in order to provide satisfactory antibacterial activity) whilst retaining desirable physical properties (i.e. satisfactory textile processing ability) were therefore achieved, with respect to the fibres having potential application as wound dressing materials. (C) 2003 Elsevier Ltd. All rights reserved.