Insights into the Antimicrobial Mechanism of Piezoelectric Materials

Physical disruption of bacterial integrity with piezoelectric materials offers a promising alternative to conventional bactericidal chemical treatments. In this study, we investigated the mechanisms of the antibacterial effect of mechanically stimulated poly-(vinylidene fluoride-<i>co</i>-trifluoroethylene) (P-(VDF-TrFE)) piezoelectric material on <i>Escherichia coli</i> cells with modified cell wall layers. Cells with modified peptidoglycan layer, outer membrane, or extracellular polymer matrix were tested for piezoelectric susceptibility either in direct contact with the piezoelectric material or in suspension after mechanical stimulation of the piezoelectric material, during the exponential and stationary growth phase. The results show that the P-(VDF-TrFE) material can electrostatically inhibit the growth of <i>E. coli</i>. The antibacterial efficacy can be further enhanced by the piezoelectric effect under mild mechanical stimulation at 1 Hz. Since most chemical antibacterial agents are effective against exponentially growing bacterial cells, it is a significant finding that piezoelectric stimulation is also very effective against stationary cells. The reduction of surface charges by cell wall modifications increased the resistance of bacteria to the electrostatic effects of P-(VDF-TrFE), but the antibacterial effect could be enhanced by piezoelectricity. Piezoelectric antimicrobial enhancement was most pronounced on cells with disrupted peptidoglycan layer and extracellular matrix removed. Based on the results of this study, one can envision an application of P-(VDF-TrFE)-coated materials on "high-touch" surfaces, such as light switches, doorknobs or countertops, that could be piezoelectrically stimulated by touch, providing an efficient and seamless solution for antibacterial surfaces.