Single precursor-based synthesis of transition metal sulfide nanoparticles and evaluation of their antimicrobial, antioxidant and cytotoxic potentials

Transition metal sulfide nanoparticles are a source of attraction for different applications, especially in optoelectronics and catalysis, however, their uses in biomedicine are not well explored. To fill this vacuum, we have reported the different physical properties and biological applications of ZnS, MnS and NiS nanoparticles synthesized by a single precursor-based route. Techniques like p-XRD, UV–Vis, TEM and TGA were used to establish their physical properties, whereas, there in vitro antibacterial, antifungal, antioxidant, cytotoxic and hemolytic potential were studied. XRD pattern revealed a single pure phase and sharp peaks owing to the crystalline nature of the nanoparticles. TEM images indicated a different morphology (spherical to cube like) while the size of the nanoparticles was in the order of ZnS (6.5 nm) < MnS (13–24 nm) < NiS (50–90 nm). Antimicrobial potential was established using well-diffusion assay across different concentrations (250 µg/mL to 4 mg/mL). It was observed that the MnS nanoparticles inhibited all of the bacterial strains in the up to 500 µg/mL, however, at 250 µg/mL, 7 and 6.5 mm inhibition zones were revealed for B. subtilis and E. coli, respectively, while the other strains revealed no susceptibility. NiS nanoparticles inhibited S. epidermidis across all the tested concentrations and revealed inhibitory zones from 10 to 6.5 mm across 4 mg/mL to 250 µg/mL. As compared to the antibacterial properties, it was observed that the metal sulfides revealed excellent antifungal potential. All of the tested fungal strains revealed zones of inhibition across the tested concentrations of MnS, NiS and ZnS. Furthermore, the highest concentration i.e. 4 mg/mL revealed high potency then positive control in some cases for example the NiS revealed zone of 20 mm as compared to the 13 mm of antibiotic for A. niger. DPPH free radical scavenging potential was found as MnS-NPs > NiS-NPs > ZnS-NPs. Brine shrimp lethality and hemolysis assays revealed cytotoxic and hemolytic nature which decreased in a dose dependent manner. Our insights into the application of metal sulfide nanoparticles reveals promises, however, we strongly encourage studies on the mechanistic aspects as well as their toxicity in vivo.