Carbon-based nanocoatings with advanced antimicrobial performance

Introduction: The development of advanced coatings can play a pivotal role in combating antimicrobial resistance infections and the severe threats they pose to modern societies. To this end, the presentation will focus on a new family of layer-by-layer antimicrobial coatings that capitalise on the electrostatic attractions between negatively charged Nafion and positively charged graphene quantum dots (GQDs) and graphene oxide (GO). Methods: Quartz crystal microbalance is used to monitor the build-up of nanocoatings in real time. Zeta potential measurements, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and contact angle measurements were used to characterise the materials that were also assessed with respect to their antimicrobial performance against E. coli and S. aureus. Results: Nafion demonstrates superior chemical, thermal, and mechanical stability stemming from its Teflon-like backbone coupled with its long-range bacteria exclusion zone (EZ) associated with the presence of charged pendant groups. The chemical modes of the bactericide activity of GQDs and GO are related to the induction of membrane stress and the release of reactive oxygen species (ROS), as well as binding with DNA to restrain cell proliferation and arrest gene expression. The Nafion/GO and Nafion/GQD nanocoatings can effectively inhibit the growth of representative Gram-positive and Gram-negative bacteria by more than 99%, and this performance is not compromised following extensive thermal annealing. Conclusion: In addition to their excellent antimicrobial performance, the nanocoatings combine a number of attractive characteristics including structural and chemical stability, non-toxic characteristics, superior UV barrier properties along with their waterborne, transparent, and colourless nature. The nanocoatings are able to withstand dry heat sterilisation and are ideal for surgical blades, surfaces used for food processing and storage, and packaging for cosmetics, drugs, and biological materials.