Amin Amani, Vivien Nagy, Sankar Rathinam and Már Másson
Introduction
Chitosan, a biopolymer derived from chitin, is well-known for its biocompatibility and antimicrobial properties. The antimicrobial activity of chitosan is notably influenced by its molecular weight (MW), which can be modulated through controlled degradation processes.
Methods
Chitosan was subjected to a controlled degradation process by stirring in 0.6 M hydrochloric acid at 70°C. At predefined time intervals, samples were extracted and subsequently precipitated in ethanol before being dried under vacuum. The molecular weight of the degraded chitosan was determined using gel permeation chromatography (GPC). Antimicrobial activity of the degraded chitosan against various gram-negative and gram-positive bacterial strains was evaluated using Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) methods.
Results
This study demonstrated a direct correlation between the duration of acid treatment of chitosan and the subsequent decrease in its MW; specifically, a longer acid exposure time consistently led to a lower molecular weight. Moreover, the results showed that a reduction in MW of chitosan significantly decreased its antibacterial activity. For instance, the MIC value for Staphylococcus aureus increased substantially from 62 µg/mL to 3072 µg/mL as the MW of chitosan decreased from 320 kDa to 6.8 kDa. Similar trends were observed in the antibacterial activity against other tested bacterial strains.
Conclusions
A significant decrease in molecular weight leads to a pronounced reduction in its ability to inhibit bacterial growth, underscoring the importance of molecular weight management in the practical application of chitosan as an antimicrobial agent.
