Design of Nanosilver-Epoxy Films for Hygienic Pharmaceutical Packaging

Nanosilver-in-epoxy lining can serve as self-disinfecting coating in pharmaceutical packaging materials and surfaces. Silver nanoparticles were synthesized using antioxidant-rich fractions of the methanolic extracts of Alchornea cordifolia . The concentration ratio of extract to silver nitrate was varied (from 2:1, 1:1 to 1:4) to obtain several batches of silver nanoparticles (A to F). The resulting silver nanoparticles were characterized using UV-visible spectroscopy, photon correlation spectroscopy, and atomic force microscopy. Antimicrobial activities of the batches of silver nanoparticles were tested in vitro using selected bacteria and fungi. Different volumes of the optimized silver nanoparticles solution were mixed with epoxy resin in different ratios, resulting in film 1 (21% v/v) and film 2 (40% v/v). Square films were cut from the coated substrate and their antimicrobial inhibition, eye irritation, and other properties tested. The optimized silver nanoparticles (batch D) were obtained by reacting the extract and silver nitrate in a 1:2 ratio, and it exhibited an excellent activity against both gram-positive and gram-negative organisms as well as fungi. It also exhibited the lowest 2-month particle size and polydispersity. Films 1 and 2 differed significantly in bioactivity ( P < 0.05), with film 2 demonstrating a good level of inhibition against Escherichia coli , Staphylococcus aureus , and Salmonella typhi , but not fungi. It did not elicit any irritation using the Draize eye irritation model. Silver nanoparticle-in-epoxy matrix synthesized with the extract maintains an adequate level of antibacterial activity and finds application in protecting surfaces and packages where bacterial contamination may pose a problem.