The impacts of green synthetized 0-to 3-dimentional Ag nanostructures on polyspecies microbial biofilms and dermocompatibility

Green synthetized Ag nanoparticles are increasingly used as antimicrobial agents topically applied to human skin for sanitization and medical purposes. Despite the widespread use, little was known on their antibiofilm efficacy and dermocompatibility. This study reports a systematic investigation into the impacts of green synthetized 0–3D Ag nanostructures, including 0D nanospheres, 1D nanowires, 2D nanoprisms and 3D nanoflowers as well as Ag nanospheres modified by different phytochemicals, on anti-biofilm efficacy and biocompatibility at the nano-skin interface. It was revealed that varying the Ag morphology induces distinct effects on two established polyspecies models consisting of skin-borne microbes ( S. aureus-S. epidermidis and S. aureus-C. albicans ). Ag nanospheres and nanowires are advantageous in inhibiting the formation of early biofilms (47–61 %) while Ag nanoprisms and nanoflowers are more effective in destroying mature biofilms (68–70 %). ROS-mediated oxidative stress, physical damage to cell membrane integrity, “contact killing” of microbial cells and suppression of adhesion-related gene expression are mechanisms involved in the anti-biofilm actions of these green synthetized Ag nanostructures. Furthermore, the dermocompatibility assessments were performed in reconstructed human epidermis. Although all exposed epidermis models remained > 50 % tissue viability, more Ag nanospheres were transdermally adsorbed than other morphologies while Ag nanoprisms were shown to be more cytotoxic. These findings provide insights into the impacts of 0–3D green synthetized Ag nanostructures on skin-borne polyspecies biofilms and dermocompatibility at the nano-skin interface, highlighting the importance of taking morphology and phytochemical modification into consideration for the rational design of sustainable Ag-based antimicrobials tailored for topical applications.