Characterization, Antimicrobial Activity, and Mechanism of a High-Performance (-)-Epigallocatechin-3-gallate (EGCG)-CuII/Polyvinyl Alcohol (PVA) Nanofibrous Membrane

(-)-Epigallocatechin-3-gallate (EGCG) exhibited strong antimicrobial activity. However, the easy oxidation of EGCG has limited its application. To increase the antimicrobial activity and stability of EGCG, the EGCG-Cu-II complex was formed by chelating copper ions and then electronspun into polyvinyl alcohol (PVA) nanofibers. Electronspun nanofibrous membranes were investigated by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), which showed that the average fiber diameter was 210 nm. Minimal inhibitory concentrations (MICs) of EGCG-Cu-II/PVA membranes were tested against the tested strains. The bactericidal activity of EGCG-Cu-II was suppressed by ethylenediaminetetraacetic acid (EDTA). Cell killing was accompanied by the leakage of intracellular proteins, indicating that the cytoplasmic membrane was badly damaged after exposure to the EGCG-Cu-II/PVA membrane. We observed the process of cell damage by SEM. On the basis of experimental evidence and theoretical analyses, the mechanism proposed that copper ions played a cooperative role in the bactericidal process of EGCG. To evaluate the antimicrobial activity of the EGCG-Cu-II/PVA membrane, we developed a rapid detection method by labeling cells with water-soluble CdTe quantum dots.