Chitosan-Thioglycolic Acid as a Versatile Antimicrobial
Agent
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Abstract
As
functionalized chitosans hold great potential for the development
of effective and broad-spectrum antibiotics, representative chitosan
derivatives were tested for antimicrobial activity in neutral media:
trimethyl chitosan (TMC), carboxy-methyl chitosan (CMC),
and chitosan-thioglycolic acid (TGA; medium molecular
weight: MMW-TGA; low molecular weight: LMW-TGA). Colony forming assays
indicated that LMW-TGA displayed superior antimicrobial activity over
the other derivatives tested: a 30 min incubation killed 100% Streptococcus sobrinus (Gram-positive bacteria) and
reduced colony counts by 99.99% in Neisseria subflava (Gram-negative bacteria) and 99.97% in Candida albicans (fungi). To elucidate LMW-TGA effects at the cellular level, microscopic
studies were performed. Use of fluorescein isothiocyanate (FITC)-labeled
chitosan derivates in confocal microscopy showed that LMW-TGA attaches
to microbial cell walls, while transmission electron microscopy indicated
that this derivative severely affects cell wall integrity and intracellular
ultrastructure in all species tested. We therefore propose LMW-TGA
as a promising and effective broad-band antimicrobial compound