Development of bioconjugated nano-molecules against targeted microbial pathogens for enhanced bactericidal activity

Abstract The study reports development of bio-conjugated nano-molecules (BCM's) for enhanced antibacterial activity against targeted pathogens of global concern. The conjugation was achieved with biomolecular interaction of silver clusters with 3-Dichloro-5, 6-dicyano-1, 4-benzoquinone (DDQ) which was purified and characterized with TLC which displayed prominent band at Rf 0.5 and HPLC analysis displayed chromatographic peak eluting at (tR) 6–8 min. The LC-MS analysis displayed single major peak at tR = 4.610 corresponding to molecular ion peak at m/z = 227.19. The developed BCM molecule was determined with UV–Visible spectroscopy which displayed the absorbance peaks of conjugated molecules with shoulder peak observed and morphological characteristics were well defined with TEM analysis which showed cluster formation. The size ranged from 20 to 80 nm in size with majority of the BCM displaying spherical in size. The process of bio-conjugation was further studied with FTIR analysis which corresponded with different vibrational stretches owing to the presence of amide, carbonyl alkynes, nitriles and carboxylic acid groups. The presence of functional moieties was also studied using 1H and 13C NMR spectra. The crystalline characteristics was confirmed with XRD analysis which displayed Bragg's intensities along with additional peaks occurring at 2 theta angle corresponds to (111), (200), (220), (311) face centric cube of silver planes. The antibacterial activity of BCM's was profound against all the test pathogen which was validated and compared with standard antibiotics. Among the test pathogens, highest activity was conferred against Staphylococcus epidermidis (MTCC 435) with 29 mm. The minimal inhibition concentration of BCM's was in the range of 0.97–3.12 μg/ml. The results of MIC were in accordance with well diffusion assay indicating the Gram + ve test pathogen Staphylococcus epidermidis to be the most sensitive. In addition, the broth dilution assay resulted in decrease in the optical density measured at 600 nm against the increase in the concentration of BCM's. The outcome of the present investigation revealed the role of bio-conjugation chemistry to increase fold activity against pathogens which can act as alternative tool to combat drug resistant menace across the globe.