Chitosan
Chitosan is a deacetylated derivate of chitin, which is a natural
polysaccharide mainly derived from the shells of
shrimps and other sea crustaceans. Chemically, it can be
designated as poly-β-(1→4)-D-glucosamine or poly-(1,4)-
2-amido-deoxy-β-D-glucose (Figure 10A) [55]. In addition
to its antimicrobial activity, chitosan has some important
advantages such as non-toxicity, biocompatibility and biodegradability.
To provide an antimicrobial agent for textiles,
chitosan can be used as an additive when spinning antimicrobial
fibers [56–58] and also as a finishing agent [59–70]
for surface modification, mainly of cellulose, cellulose/polyester
and wool fibers. Chitosan is positively charged and soluble
in acidic to neutral solutions because the amino
groups in chitosan have a pKa of ~6.5. Its antimicrobial
function arises from its polycationic nature, which is
caused by protonation of the amino groups at the C-2
atoms of the glucosamine units; such antimicrobial function
is very similar to that determined for QAS. Positively
charged amino groups can bind to the negatively charged
bacterial surface, resulting in the disruption of the cell membrane
and an increase in its permeability. Chitosan can also
interact with the DNA of microorganisms to prevent protein
synthesis. The antimicrobial efficiency of chitosan depends
on its average molecular weight, degree of deacetylation and
the ratio between protonated and unprotonated aminomers incorporating N-halamine siloxane and QAS siloxane
enhances the antimicrobial action of these agents in combination