Contact-Dependent Antibacterial Performance of Silver Nanoparticles Encapsulated in Collagen-Based Gels

The design of new medical devices in biomedical engineering often necessitates the control of microbial load at the point of application, making antibacterial action valuable for numerous applications in the biomedical field. Nanotechnology products, such as silver nanoparticles (AgNPs), represent highly promising yet underexplored bioactive and antimicrobial agents that have attracted researchers' interest for integration into medical devices. This study focuses on stable suspensions of silver nanoparticles, characterized by using a range of complementary physicochemical techniques as well as bacterial cell cultures, while also demonstrating controlled entrapment of the nanoparticles in collagen-based gels. The findings reveal that highly stable suspensions of negatively charged AgNPs (~6 nm in size) consistently exhibit broad-spectrum antimicrobial activity against both Gram-negative and Gram-positive bacteria, with minimum inhibitory concentration values of 10-20 ppm, whilst, importantly, close contact between the nanoparticles and bacterial cells turns out to be essential for their antibacterial action. Controlled entrapment of the nanoparticles in collagen-based gels enables regulation of nanoparticle release and their antimicrobial efficacy. This work highlights the promising prospects of silver nanoparticles in designing novel biomedical engineering products, while underscoring the need for a more comprehensive understanding of their biological activity to ensure optimal utilization.