Researchers have looked into two bioadhesive polymers – cationic chitosan (made from the shells of crustaceans – see below) and anionic polycarbophil – with the intention of disrupting the negatively-charged polysaccharide matrix biofilms present in bacterial vaginosis that prevent antibiotic penetration.
The bacteria studied was Pseudomonas aeruginosa, a biofilm-developing microbe. Note that this bacteria is not a bacteria commonly found in bacterial vaginosis.
The study
The P. aeruginosa biofilms were treated with various concentrations of polycarbophil and chitosan at pH of 4 or 6. Biofilm integrity was then tested and evaluated, demonstrating that chitosan gel disrupts the biofilm of P. aeruginosa biofilms more effectively than polycarbophil. This effect was independent of the pH and charge densities of either polymer.
Key findings of the study:
- The disruptive effect of chitosan is similar at a pH of 4 and 6
- Charge density is not important in chitosan’s ability to disrupt biofilms
- Biofilm disruption increased at pH 6 with higher chitosan concentrations of 1 per cent and 0.5 per cent
- Biofilm integrity did not seem to change with extended treatment times past one hour at either pH 4 or 6
- The polycarbophil treatment did not increase the dead cell number at one hour or beyond
- Chitosan gels were effective at disrupting the biofilm integrity and causing bacterial cell death at concentrations as low as 0.13 per cent at both pH 4 and 6
- Polycarbophil gels showed comparable effects at higher concentrations of 1 per cent at pH 4, but not 6
- Metronidazole-containing chitosan gels may be more effective at treating BV than polycarbophil gels
What is chitosan?
Chitosan is a sugar made by treating the chitin shells of shrimps, crabs, lobster, crayfish and other crustaceans with an alkaline substance. Chitosan is used in multiple industries from farming to winemaking to biomedicine, as pesticides and antimicrobials. Chitosan is also used as a form of soluble dietary fibre. Chitosan is water soluble and bioadhesive due to its charge, and readily binds to negatively charged surfaces, including mucosal surfaces as found in the vagina and mouth.
The reason chitosan is useful in biomedicine is because it enhances the transport of drugs across the skin, it is biocompatible, and biodegradable. It is also found in abundance in nature.
Current uses of chitosan:
- Natural seed treatment
- Plant growth enhancer
- Ecologically friendly biopesticide against fungal infections in plants
- Plant protection for plants in space
- Water filtration
- Fining agent in winemaking (fungal sources)
- Rapid blood clotting agent used in bandages
- Transdermal drug delivery
- Temporary bone filler
- Self-healing scratch repairing coating
- 3D printing
- Food preservation
References
Ability of Chitosan Gels to Disrupt Bacterial Biofilms and Their Applications in the Treatment of Bacterial Vaginosis, Kandimalla, Karunya K. et al. Journal of Pharmaceutical Sciences , Volume 102 , Issue 7 , 2096 – 2101
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