Super effective antimicrobial silver-sputtered coatings on poly(lactic acid) against bacteria and omicron SARS-CoV-2

Poly(lactic acid) (PLA) is a biopolymer with properties potentially suitable for fabricating packaging, medical devices, and healthcare products in a more friendly environmental way because this polymer presents biodegradability, compostability, low carbon footprint, and recyclability. However, PLA does not present intrinsic antimicrobial properties. Antimicrobial materials are highly desirable for manufacturing smart packaging and personal protective equipment to secure food and health professionals against pathogenic microorganisms. In this work, we evaluated the antimicrobial performance of (Ag)-coated PLA against Escherichia coli, Bacillus subtilis, and Omicron severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). PLA was rapidly coated with metallic Ag by pulsed direct current magnetron sputtering (pDCMS) for 5, 10, and 20 s. Atomic force microscopy indicates that the Ag coating grows predominantly on the PLA surface via a bulk diffusion mechanism. According to bactericidal and quantitative reverse transcription polymerase chain reaction assays, Ag-coated PLA was capable of inhibiting bacterial biofilm formation and disrupting the genetic material of the Omicron SARS-CoV-2. X-ray high-resolution photoelectron and nuclear magnetic resonance results suggest no polymer chain scission in the PLA bulk due to plasma thermal stress effects during Ag sputtering.