Mechanisms of Integration and Release of AgNO3 in Chitosan Films and Their Interaction with Nosocomial Pathogens

Postsurgical infections are an important cause of implant failure, and biomaterials such as Chitosan can be used as an antimicrobial coating to address this important problem. Characterization of silver distribution was performed by several methods, including Electron scanning microscopy (SEM), Inductively coupled plasma (ICP), and Infrared spectrometry (IR). Antimicrobial activity was tested against Candida albicans ATCC 10231, Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa BAA-1744 ATCC 109246. The inhibition assays showed that Chitosan films inhibited 68% of C. albicans growth and 23.5% of E. coli growth; the rest of the microorganisms did not have any statistically relevant inhibition. E. coli, P. aeruginosa, and C. albicans were completely inhibited in films with 0.25 mg/mL of AgNO3 and inhibited 82.5% of S. aureus. The mechanism of integration and release of silver in the films was analyzed by the Density Functional Theory (DFT), considering this analysis of geometry optimization as well as infrared spectroscopy. DFT analysis showed that AgNO3 is not trapped by covalence in chitosan, being a more stable system when it is closer to an OH group. Chitosan films functionalized with antimicrobial compounds are a promising antimicrobial coating for use in biomaterials to prevent postsurgical complications.