Antimicrobial Chitosan Conjugates: Current Synthetic Strategies and Potential Applications

Abstract

As a natural polysaccharide, chitosan possesses good biocompatibility, biodegradability and biosafety. Its hydroxyl and amino groups make it an ideal carrier material in the construction of polymer-drug conjugates. In recent years, various synthetic strategies have been used to couple chitosan with active substances to obtain conjugates with diverse structures and unique functions. In particular, chitosan conjugates with antimicrobial activity have shown great application prospects in the fields of medicine, food, and agriculture in recent years. Hence, we will place substantial emphasis on the synthetic approaches for preparing chitosan conjugates and their antimicrobial applications, which are not well summarized. Meanwhile, the challenges, limitations, and prospects of antimicrobial chitosan conjugates are described and discussed.

Keywords: antimicrobial activity; applications; chitosan; conjugates; synthetic approach.

Figure 1

Number of publications searched containing “antimicrobial chitosan conjugate” keywords via ISI Web of Science (A); Classification and proportion of corresponding chitosan conjugates (B); Note: The data for 2019 are as of the end of November.

Figure 2

Proposed mechanism of synthesis of polyphenol chitosan conjugate by free radical induction reaction.

Figure 3

Proposed mechanism of synthesis of a chitosan conjugate by a carbodiimide based chemical coupling method.

Figure 4

Functional group conversion strategies commonly used in the synthesis of chitosan conjugates.

Figure 5

Proposed mechanism for the synthesis of polyphenol-chitosan conjugates through an enzyme-mediated strategy.

Figure 6

Effect of CA NPs on prefabricated biofilms formed by gram-negative and gram-positive organisms. Biofilm produced by Pseudomonas aeruginosa (A), Salmonella typhimurium (B), Listeria monocytogenes (C), and Staphylococcus aureus (D) treated with CA NPs (250 mg/mL), CS (250 mg/mL), streptomycin (Strep, 50 mg/mL) for 24 h; After 24 h of treatment, pre-formed biofilm structures of Pseudomonas aeruginosa (E) and Staphylococcus aureus (F) under a fluorescence microscope (Scale bar represented for 10 μm); After 24 h of treatment, pre-formed biofilm structures of Pseudomonas aeruginosa (G) and Staphylococcus aureus (H) under a scanning electron microscopy (Scale bar represented for 400 nm). Reprinted with permission from [37].