Interaction of Silver Nanoparticles and Chitin Powder with Different Sizes and Surface Structures: The Correlation with Antimicrobial Activities

Abstract

Silver nanoparticles (Ag NPs) were 5.17 ± 1.9 nm in diameter, and four <5% deacetylated chitins (A, B, C, and D) differing in size of powder and surface structure properties were used in the study. Chitin/Ag NP composites were synthesized by mixing Ag NP suspensions with each chitin powder at room temperature for 30 min. The Ag NPs were homogenously dispersed and stably adsorbed onto the chitins A and B powders. The resulting chitin/Ag NP composites were brown; darker composites were obtained when larger amounts of Ag NPs were reacted with chitin. Approximately, 26 and 22 μ g of Ag NPs maximally adsorbed to 1 mg of chitins A and B, respectively, whereas only 2.5 and 1.5 μ g of Ag NPs maximally adsorbed to chitins C and D, respectively. As the bactericidal and antifungal activities of the chitin/Ag NP composites increased with increasing amounts of Ag NPs adsorbed to the chitin, the antimicrobial activity of chitins A and B/Ag NP composites was much higher than that of chitins C and D/Ag NP composites. These results suggest that the particle size and surface structure of the chitin powder critically influence both the adsorption and antimicrobial activity of Ag NPs.