Influence of the chain length of chitosan on complement activation

Non-water soluble chito-oligosaccharides (COSs) (molecular weights: 8, 800; 14, 200; 18, 200; and 33, 000) were investigated for complement activation by the single radial immuno-diffusion method. C3 activation was increased in a chain length-dependent manner. On regression analysis, there was significant correlation (P<0.01) between the number of NH2 group of COSs and the extent of C3 activation after 20 min of incubation. The binding of C3b to chitosan (82% deacetylated chitin) was also investigated by an immunofluorescence method, and binding of C3b to chitosan particles was clearly observed. From these results, number of amino groups, and trapping of C3b are important evidence of complement activation via alternative pathway by chitosan and non-water soluble COSs.