Comparative study of antibacterial activity between Schiff base nicotinic hydrazide derivative and its silver architected nanoparticles with atomic force microscopic study of bacterial cell wall.

The threat of multi-drug resistant bacterial pathogens evokes researchers to synthesized safe and effective chemotherapeutic agents for nano-drug delivery system. In current study, Schiff base of nicotinic hydrazide(NHD) and its silver nanoparticles(NHD-AgNPs) were synthesized and characterized. These compounds were investigated for cytotoxicity, antibacterial and AFM activity. The NHD showed LD50 at >1000μg/mL while NHD-AgNPs didn't exhibit toxicity at 1000μg/mL against 3T3 cell line. The NHD showed zone of inhibition against two strains of salmonella enteric (ATCC 14028 and 700408) 45.29±1.66 and 48.01±1.43mm respectively at 160μg/mL (p<0.01) while NHD-AgNPs exhibited 55.87±2.08 and 52.88±1.42 mm respectively at 130μg/mL (p<0.001) in disc diffusion method. NHD showed more than 70% growth inhibition for both strains at 85 and 125μg/ml (p<0.01) respectively, while NHD-AgNPs inhibit 80% and 75% respectively at 75 and 125 μg/ml (p<0.01, p<0.001) against Alamar blue antibacterial assay. For morphological changes in bacterial cell wall NHD and NHD-AgNPs treated bacterial cells were observed under atomic force microscope(AFM) and treated bacterial cells were severely damaged with leaked cytoplasmic contents as compare to untreated bacterial cell. These results validate that NHD-AgNPs were highly active as compared to NHD against both strains at their MIC concentrations. In future, comparative wound healing potential will be emphasized.