Detection of bacterial contaminants via frequency manipulation of amino-groups functionalized Fe3O4nanoparticles based resonant sensor.

Bacterial infections have a large impact on public health. Through this study, we report on the development of complementary split-ring resonators (CSRR) supplemented by functionalized nanoparticles to detect bacteria in the aqueous medium. Iron oxide (Fe3O4) nanoparticles were functionalized with amino groups using (3-aminopropyl) triethoxysilane (APTES) to form (APTES@Fe3O4) nanoparticles, which have a specific affinity towards the bacterial species. This affinity was evaluated using theEscherichia coli (E. coli)andStaphylococcus aureus (S. aureus)bacterial species. The resonant sensor was tuned at 430 MHz and the CSRR sensor bed was further activated using APTES@Fe3O4nanoparticles. Bacterial detection was studied over a range of concentrations from 2.66 × 109cells to 2.66 × 108cells. The sensor actively responded to small changes in bacterial concentration, showing an overall shift in resonance frequency of âˆ¼44 MHz (∼40 MHz/cell count) forE. coliand âˆ¼55 MHz (50.43 MHz/cell count) forS. aureus. Dextran sulphate and Chitosan were used as the references. The magnetic character of the conjugated system exhibited strong interaction of the bacterial species with APTES@Fe3O4, justifying the high selectivity towards these species. This demonstrates the feasibility of a sensitive, fast, portable device, against the traditionally used time-consuming bio-assays.

Self-assembly of soybean peroxidase nanohybrid for activity enhancement and dye decolorization: experimental and computational studies.

The soybean peroxidase (SBP) mediated nanohybrid [SBP-Cu3(PO4)2·3H2O] synthesis was carried out in the present study. The scanning electron microscopy (SEM) analysis showed a characteristic flower-like hierarchical structure of the SBP-nanohybrid. The mechanism of SBP-nanohybrid formation was elucidated using computational approaches. The predicted Cu2+ binding sites followed by molecular docking studies showed the two lowest energy (-4.4 kcal/mol and -3.56 kcal/mol) Cu2+ binding sites. These two binding sites are located at the opposite position and might be involved in the formation of SBP-nanohybrid assemblies. Further, these sites are different than the catalytic active site pocket of SBP, and may facilitate more substrate catalysis. Obtained computational results were confirmed by in-vitro guaiacol oxidations studies using SBP-nanohybrid. The effect of various parameters on SBP-nanohybrid activity was studied. The pH 7.2 was found optimum for SBP-nanohybrid activity. The enzyme activity increased with an increase in temperature up to 50 °C temperature and then decreased with an increase in temperature. Around ∼138% enhanced activity was recorded using SBP-nanohybrid compared to crude SBP. Also, the SBP-nanohybrid showed around 95% decolorization of methylene blue (MB) in 1 h and the MB degradation was confirmed by high-pressure liquid chromatography analysis (HPLC).Communicated by Ramaswamy H. Sarma.

Exploration of intrinsic peroxidase-like activity of Acidithiobacillus ferrooxidans spent medium and its application for glutathione detection.

Acidithiobacillus ferrooxidans (At. ferrooxidans) is a bacterium that has the ability to metabolize iron. It converts Fe2+ into Fe3+ during its metabolic cycle. Hence, the At. ferrooxidans spent medium is rich in Fe3+. The presence of Fe3+ contributes to a peroxidase-like activity. Therefore, in this study, an attempt has been made to explore the peroxidase-like activity of the At. ferrooxidans spent medium. It has been observed that the At. ferrooxidans spent medium oxidized 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). The effect of various process parameters on the peroxidase-like activity has been studied. Optimum peroxidase-like activity is achieved using 5 µl of the spent medium, 0.3 mM TMB concentration, 4 mM H2O2 concentration, 4.2 pH, and 40 °C temperature. The peroxidase-like activity of the At. ferrooxidans spent medium has been used to develop a colorimetric assay for detection of glutathione (GSH). GSH inhibits the peroxidase-like activity of the At. ferrooxidans spent medium in a concentration range of 0-1 mM. The limit of detection (LOD) of GSH, obtained using the calibration plot is 0.69 mM. The developed assay is selective toward GSH, as the presence of amino acids, metals, and sugars have shown a negligible effect on the GSH sensing ability.

Bioleaching of copper from large printed circuit boards for synthesis of organic-inorganic hybrid.

The present study described a process for copper (Cu) bioleaching from waste printed circuit boards (PCBs). The 45 (± 0.18) mg/g Cu was found in waste PCBs. Acidiphilium acidophilum (NCIM 5344) (A. acidophilum) and hydrogen peroxide (H2O2) were used for two-step Cu bioleaching. A. acidophilum showed growth in 9K medium containing glucose and sulfur. During the growth the bacteria decreased medium pH from 3.5 (± 0.01) to 1.0 (± 0.02) in 10 days. The results showed that it required 2.5 h to leach all of the Cu from single PCB piece using 60 mL culture supernatant + 15 mL H2O2 at 60 °C temperature and static condition. The leached Cu was further used to synthesize the organic-inorganic hybrid (OIH). For this study, egg white was used as a polyphenol oxidase (PPO) enzyme source. The morphological, elemental, and structural analysis was carried out using scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Further the PPO enzyme activity was tested in OIH and crude enzyme (egg white). The egg white showed 0.00014 (± 0.00001) U/mg/min PPO activity while OIH showed 0.005 (± 0.00016) U/mg/min PPO activity. The pH 7 and 30 °C temperature were found to be optimum for PPO enzyme activity. The OIH was applied for phenol degradation. It degraded 95 (± 0.49)% of phenol (5 mM). The efficiency of phenol degradation decreased with an increase in phenol concentration.