ABSTRACT
The present study used a sol-gel auto-combustion approach to make silica (SiO2)-coated Ni-Co ferrite nanocomposites that would be used as a platform for enzyme immobilization. Using glutaraldehyde as a coupling agent, glucose oxidase (GOx) was covalently immobilized on this magnetic substrate. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), and fourier transform infrared spectroscopy (FTIR) was used to determine the structural analysis and morphology of Ni-Co ferrite/SiO2 nanocomposites. FTIR spectra confirmed the binding of GOx to Ni-Co ferrite/SiO2 nanocomposites, with a loading efficiency of around 85%. At alkaline pH and higher temperature, the immobilized GOx enzyme exhibited increased catalytic activity. After 10 times of reuses, it still had 69% catalytic activity. Overall, the immobilized GOx displayed higher operational stability than the free enzyme under severe circumstances and was easily recovered by magnetic separation. With increased doping concentration of the nanocomposites, the photocatalytic activity was assessed using a degradation process in the presence of methylene blue dye under UV light irradiation, which revealed that the surface area of the nanocomposites with increased doping concentration played a significant role in improving photocatalytic activity. The antibacterial activity of Ni-Co ferrite/SiO2 nanocomposites was assessed using the agar well diffusion method against Escherichia coli, a gram-negative bacteria (ATCC 25922). Consequently, it was revealed that doping of Ni2+ and Co2+ in Fe2O4/SiO2 nanocomposites at varied concentrations improved their antibacterial properties.
ABSTRACT
Sn1-xCoxO2 (x=0.00, 0.01, 0.03, 0.05) nanoparticles (NPs) of average size â¼30-40nm were synthesized by co-precipitation method. The interaction of Co doped SnO2 NPs with human serum albumin (HSA) and their photocatalytic and antimicrobial properties were studied. The structural analysis and morphology of Co doped SnO2 NPs were analysed via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FT-IR). Besides the structural and morphological analysis, the interaction of Co doped SnO2 NPs with HSA were studied by UV-vis, Circular dichroism (CD) and fluorescence spectroscopy. Fluorescence quenching results suggest that Co doped SnO2 NPs interact with an HSA molecule through static mechanism. CD indicates that α-helicity of HSA increases due to the interaction of Co doped SnO2 NPs. The photocatalytic activities of the NPs with increased doping concentration were evaluated through a degradation process in the presence of methylene-blue (MB) dye under UV light irradiation, which exhibited that the surface area of NPs with increased doping concentration plays a major role in improving the photocatalytic activity. The antimicrobial effect of undoped and Co-doped SnO2 NPs was determined using agar-well diffusion method and analyzed against gram-positive bacteria (Bacillus Cereus MC 2434). In our results, we have found that as the doping concentration increases into NPs, zone of inhibition increases, which could be ascribed to the production of ROS and large surface area of the NPs.
Subject(s)
Anti-Infective Agents/chemical synthesis , Cobalt/chemistry , Metal Nanoparticles/chemistry , Serum Albumin/chemistry , Tin Compounds/chemistry , Anti-Infective Agents/pharmacology , Bacillus cereus/drug effects , Bacillus cereus/growth & development , Chemical Precipitation , Cobalt/pharmacology , Disk Diffusion Antimicrobial Tests , Humans , Light , Metal Nanoparticles/ultrastructure , Methylene Blue/chemistry , Photochemical Processes , Protein Conformation, alpha-Helical , Reactive Oxygen Species/agonists , Reactive Oxygen Species/metabolism , Spectrometry, Fluorescence , Tin Compounds/pharmacologyABSTRACT
The covalent binding of yeast alcohol dehydrogenase (YADH) enzyme complex in a series of magnetic crystalline Ni-Co nanoferrites, synthesized via sol-gel auto combustion technique was investigated. The structural analysis, morphology and magnetic properties of Ni-Co nanoferrites were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), vibrating-sample magnetometer (VSM), high resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FTIR). The comparative analysis of the HRTEM micrographs of bare magnetic nanoferrite particles and particles immobilized with enzyme revealed an uniform distribution of the particles in both the cases without undergoing change in the size which was found to be in the range 20-30 nm. The binding of YADH to Ni-Co nanoferrites and the possible binding mechanism have been suggested by comparing the FTIR results. The binding properties of the immobilized YADH enzyme were also studied by kinetic parameters, optimum operational pH, temperature, thermal stability and reusability. The immobilized YADH exhibits enhanced thermal stability as compared to the free enzyme over a wide range of temperature and pH, and showed good durability after recovery by magnetic separation for repeated use.
