METHODS: B. subtilis was exposed to 5 to 150 μg/mL of ZnO NPs for 24 h. The parameters employed to evaluate the antimicrobial potential of ZnO NPs were the growth inhibitory effect on B. subtilis, the surface interaction of ZnO NPs on the bacterial cell wall, and also the morphological alterations in B. subtilis induced by ZnO NPs.
RESULTS: The results demonstrated a significant (p <0.05) inhibition of ZnO NPs on B. subtilis growth and it was in a dose-dependent manner for all the tested concentrations of ZnO NPs from 5 to 150 μg/mL at 24 h. Fourier transformed infrared (FTIR) spectrum confirmed the involvement of polysaccharides and polypeptides of bacterial cell wall in surface binding of ZnO NPs on bacteria. The scanning electron microscopy (SEM) was used to visualize the morphological changes, B. subtilis illustrated several surface alterations such as distortion of cell membrane, roughening of cell surface, aggregation and bending of cells, as well as, the cell rupture upon interacting with ZnO NPs for 24 h.
CONCLUSION: The results indicated the potential of ZnO NPs to be used as an antibacterial agent against B. subtilis. The findings of the present study might bring insights to incorporate ZnO NPs as an antibacterial agent in the topical applications against the infections caused by B. subtilis.
METHODS: The structures of all synthesized compounds were characterized by physicochemical properties and spectral means (IR and NMR). The synthesized compounds were evaluated for their in vitro antimicrobial activity against Gram-positive (B. subtilis), Gram-negative (P. aeruginosa and E. coli) bacterial and fungal (C. albicans and A. niger) strains by tube dilution method using ciprofloxacin, amoxicillin and fluconazole as standards. In-vitro antioxidant and anti-urease screening was done by DPPH assay and indophenol method, respectively. The in-vitro anticancer evaluation was carried out against MCF-7 and HCT116 cancer cell lines using 5-FU as standards.
RESULTS, DISCUSSION AND CONCLUSION: The biological screening results reveal that the compounds T5 (MICBS, EC = 24.7 µM, MICPA, CA = 12.3 µM) and T17 (MICAN = 27.1 µM) exhibited potent antimicrobial activity as comparable to standards ciprofloxacin, amoxicillin (MICCipro = 18.1 µM, MICAmo = 17.1 µM) and fluconazole (MICFlu = 20.4 µM), respectively. The antioxidant evaluation showed that compounds T2 (IC50 = 34.83 µg/ml) and T3 (IC50 = 34.38 µg/ml) showed significant antioxidant activity and comparable to ascorbic acid (IC50 = 35.44 µg/ml). Compounds T3 (IC50 = 54.01 µg/ml) was the most potent urease inhibitor amongst the synthesized compounds and compared to standard thiourea (IC50 = 54.25 µg/ml). The most potent anticancer activity was shown by compounds T2 (IC50 = 3.84 μM) and T7 (IC50 = 3.25 μM) against HCT116 cell lines as compared to standard 5-FU (IC50 = 25.36 μM).