Development of polyurethane antimicrobial coatings by composition with phenolic-, ionic- and copper-based agents

Microorganisms can be found in almost all environments with high-touch surfaces being an important fomite for microbial growth. Considering the health issues associated to acquired infection from inanimate surfaces, as well as the raising hygienic concerns, the incorporation of antimicrobial compounds in high-touch surfaces emerges as an effective solution for biomedical and common daily applications. In this work we incorporated different antimicrobial agents (phenolic-, ionic- and copper-based compounds) into polyurethane commercial formulations to produce antimicrobial lacquer-films and evaluated not only their physical/chemical properties, but also their antimicrobial activity against bacteria (Staphylococcus aureus, Escherichia coli), fungi (Candida albicans), and virus (SARS-Cov-2). The incorporation of antimicrobial agents did not affect the performance of lacquer-films and the main properties were maintained, specifically the visual aspect, gloss values, optical properties and its chemical stability. Among the different compounds tested copper-based lacquer-films, exhibited the strongest antibacterial and antifungal activity, with a >4log reduction, but not against virus. Importantly, copper-based lacquer-films maintained their cytocompatibility, even at high concentrations. Regarding the ionic lacquer-films, the highest tested concentration also showed a strong antimicrobial action (5log reduction) against fungi and gram-positive bacteria, but not against gram-negative bacteria and virus. However, at this concentration the ionic-containing lacquer-films presented cytotoxic potential. The phenolic-based compounds were not associated with antimicrobial activity, regardless the concentrations tested. Collectively, these results highlight the potential of incorporating antimicrobial agents in plastic surface coatings as a promising strategy to avoid the microbial colonization on inanimate surfaces and ultimately prevent the spreading of potentially harmful pathogens among humans.

Impact of surface topography on the bacterial attachment to micro- and nano-patterned polymer films.

The development of antimicrobial surfaces has become a high priority in recent times. There are two ongoing worldwide health crises: the COVID-19 pandemic provoked by the SARS-CoV-2 virus and the antibiotic-resistant diseases provoked by bacteria resistant to antibiotic-based treatments. The need for antimicrobial surfaces against bacteria and virus is a common factor to both crises. Most extended strategies to prevent bacterial associated infections rely on chemical based-approaches based on surface coatings or biocide encapsulated agents that release chemical agents. A critical limitation of these chemistry-based strategies is their limited effectiveness in time while grows the concerns about the long-term toxicity on human beings and environment pollution. An alternative strategy to prevent bacterial attachment consists in the introduction of physical modification to the surface. Pursuing this chemistry-independent strategy, we present a fabrication process of surface topographies [one-level (micro, nano) and hierarchical (micro+nano) structures] in polypropylene (PP) substrates and discuss how wettability, topography and patterns size influence on its antibacterial properties. Using nanoimprint lithography as patterning technique, we report as best results 82 and 86% reduction in the bacterial attachment of E. coli and S. aureus for hierarchically patterned samples compared to unpatterned reference surfaces. Furthermore, we benchmark the mechanical properties of the patterned PP surfaces against commercially available antimicrobial films and provide evidence for the patterned PP films to be suitable candidates for use as antibacterial functional surfaces in a hospital environment.