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Abstract
Chitosan, which is derived from a deacetylation reaction of chitin, has attractive antimicrobial activity. However, chitosan applications as a biocide are only effective in acidic medium due to its low solubility in neutral and basic conditions. Also, the positive charges carried by the protonated amine groups of chitosan (in acidic conditions) that are the driving force for its solubilization are also associated with its antimicrobial activity. Therefore, chemical modifications of chitosan are required to enhance its solubility and broaden the spectrum of its applications, including as biocide. Quaternization on the nitrogen atom of chitosan is the most used route to render water-soluble chitosan-derivatives, especially at physiological pH conditions. Recent reports in the literature demonstrate that such chitosan-derivatives present excellent antimicrobial activity due to permanent positive charge on nitrogen atoms side-bonded to the polymer backbone. This review presents some relevant work regarding the use of quaternized chitosan-derivatives obtained by different synthetic paths in applications as antimicrobial agents.
Highlights
Infections Caused by MicroorganismsInfections by microorganisms, such as gram-positive and gram-negative bacteria, virus, fungi, and protozoa, etc., are major concerns in clinical and pharmaceutical areas (drugs, medical devices, odontology, hospital surfaces, etc.) as well as in the food industry (food packaging, storage, fresh products, etc.)
Another work showed that the chemical modification of chitosan through heterocyclic substitution and further quaternization allows the product to present an important effect in the antimicrobial activity against microbes and fungi
The results showed the TCDCMCHT and TCNCMCHT have higher antibacterial activity when compared to O-carboxymethyl chitosan and these chitosan derivatives presented good solubility compared to unmodified chitosan [56]
Summary
Infections by microorganisms, such as gram-positive and gram-negative bacteria, virus, fungi, and protozoa, etc., are major concerns in clinical and pharmaceutical areas (drugs, medical devices, odontology, hospital surfaces, etc.) as well as in the food industry (food packaging, storage, fresh products, etc.). Another work showed that the chemical modification of chitosan through heterocyclic substitution and further quaternization allows the product to present an important effect in the antimicrobial activity against microbes (gram-negative and gram-positive bacteria) and fungi. The authors found that both matrices (chitosan/CS and chitosan/CS/AgSD) exhibit activity against P. aeruginosa and S. aureus, and had no toxic effects on VERO cells, which makes the use of chitosan/CS and chitosan/CS/AgSD even more attractive All these studies, based on chitosan and chitosan-derivative activities against microorganism, clearly indicate the diversity and relevance of the research and use of chitosan and its derivatives as antimicrobial agents. The main focus was to describe some recent synthetic methodologies to obtain chitosan-derivatives containing quaternized moieties in their backbone These derivatives of chitosan present excellent antimicrobial activity at neutral condition (pH ≈ 7) and good potential for applications in the medical and pharmaceutical field. The antimicrobial mechanism of such materials will be addressed throughout each section
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