Tailoring the morphology and crystallinity of MoS2 for bacterial inhibition of Gram-negative and Gram-positive bacteria.

Antimicrobial resistance causes millions of infections and deaths each year, necessitating new approaches to minimise these effects. Here, we present a direct comparison of crystalline, MoS2 nanosheets (MNS) and amorphous MoS2 nanoflowers (MNF) against Escherichia coli MG1655 (Gram-negative bacteria) and Staphylococcus aureus RN4220 (Gram-positive bacteria). The crystalline MNS sheets of different sizes were obtained using exfoliation of bulk MoS2, while the amorphous MNF was formed using hydrothermal synthesis. Using XPS, the MNF was found to contain MoO3 in addition to MoS2, while the MNS had little or no impurities. The MNS exhibited a Zeta potential of -29.4 mV, while MNF showed a lower potential of -23.5 mV, indicating greater dispersibility of the MNS in aqueous-based biological media. Utilising a combination of Ellman's, nitroblue tetrazolium, and terephthalic acid assays, the crystalline MNS was observed to favour superoxide-linked oxidative stress, which proved particularly effective against Escherichia coli. Conversely, the amorphous MNF produced hydroxyl radicals that facilitated early GSH oxidation, thereby favouring inhibition of Staphylococcus aureus. In both cases, there was no evidence of membrane cell damage.