Synthesis of iron oxide nanoparticles mediated by Camellia sinensis var. Assamica for Cr(VI) adsorption and detoxification.

Environment-benign synthesis of nanoparticles (NPs) are of great importance. Plant-based polyphenols (PPs) are electron donor analytes for the synthesis of metal and metal oxide NPs. This work produced and investigated iron oxide nanoparticles (IONPs) from PPs of tea leaves of Camellia sinensis var. assamica for Cr(VI) removal. The conditions for IONPs synthesis were using RSM CCD and found to be optimum at a time of 48 min, temperature of 26 °C, and iron precursors/leaves extract ratio (v/v) of 0.36. Further, these synthesized IONPs at a dosage of 0.75 g/L, temperature of 25 °C, and pH 2 achieved a maximum of 96% Cr(VI) removal from 40 mg/L of Cr(VI) concentration. The exothermic adsorption process followed the pseudo-second-order model, and Langmuir isotherm estimated a remarkable maximum adsorption capacity (Qm) of 1272 mg g-1 of IONPs. The proposed mechanistic for Cr(VI) removal and detoxification involved adsorption and its reduction to Cr(III), followed by Cr(III)/Fe(III) co-precipitation.

A comparative investigation of normal and inverted exchange bias effect for magnetic fluid hyperthermia applications.

Exchange bias (EB) of magnetic nanoparticles (MNPs) in the nanoscale regime has been extensively studied by researchers, which have opened up a novel approach in tuning the magnetic anisotropy properties of magnetic nanoparticles (MNPs) in prospective application of biomedical research such as magnetic hyperthermia. In this work, we report a comparative study on the effect of magnetic EB of normal and inverted core@shell (CS) nanostructures and its influence on the heating efficiency by synthesizing Antiferromagnetic (AFM) NiO (N) and Ferrimagnetic (FiM) Fe3O4 (F). The formation of CS structures for both systems is clearly authenticated by XRD and HRTEM analyses. The magnetic properties were extensively studied by Vibrating Sample Magnetometer (VSM). We reported that the inverted CS NiO@Fe3O4 (NF) MNPs have shown a greater EB owing to higher uncompensated spins at the interface of the AFM, in comparison to the normal CS Fe3O4@NiO (FN) MNPs. Both the CS systems have shown higher SAR values in comparison to the single-phased F owing to the EB coupling at the interface. However, the higher surface anisotropy of F shell with more EB field for NF enhanced the SAR value as compared to FN system. The EB coupling is hindered at higher concentrations of NF MNPs because of the enhanced dipolar interactions (agglomeration of nanoparticles). Both the CS systems reach to the hyperthermia temperature within 10 min. The cyto-compatibility analysis resulted in the excellent cell viability (> 75%) for 3 days in the presence of the synthesized NPs upto 1 mg/ml. These observations endorsed the suitability of CS nanoassemblies for magnetic fluid hyperthermia applications.

Production of biosurfactant by Bacillus subtilis RSL-2 isolated from sludge and biosurfactant mediated degradation of oil.

This study aims to unveil the effect of biosurfactant as stimulant in crude oil bioremediation. Isolated oil-degrading strain, B. subtilis RSL 2 was optimized for the maximum oil degradation and biosurfactant production using Response surface methodology. The produced biosurfactant was characterized and investigated for its effect on microbial oil degradation in two modes (a) sequential and (b) simultaneous. The strain produced 3.5 g/L of biosurfactant at pH 4.0, 25 °C, using 1 g/L crude oil as the only C-source in 7 days, which was characterized as lipopeptide with a critical micelle concentration (CMC) of 0.5 g/L. The biosurfactant improved surface wettability of a hydrophobic substrate i.e. increased surface energy from 30 ± 1 to 35 ± 1 mJ/m2. Further, the simultaneous feed of biosurfactant at 0.5 CMC enhanced oil biodegradation (72%) and biosurfactant production (5.2 g/L) by about 1.6 times than the sequential mode due to improvement in mobilization of oil thus making it more bioavailable.

Isolation and characterization of biosurfactant producing and oil degrading Bacillus subtilis MG495086 from formation water of Assam oil reservoir and its suitability for enhanced oil recovery.

The strains isolated from the formation water were characterized and screened considering their crude oil degradation capability and biosurfactant production ability. The growth kinetics study of isolated Bacillus subtilis MG495086 was carried out by varying growth parameters i.e. carbon source, temperature, pH and salinity. The biosurfactant production was optimized adopting RSM-CCD considering carbon source (1-5%), pH (3-11) and temperature (25-65 °C) as matrix parameters. The optimum biosurfactant production (6.3 ±â€¯0.1 g/L) and the minimum surface tension 29.85 mN/m were obtained after 96 h of incubation under optimal conditions i.e. 3.8% (v/v) of light-paraffin oil as sole carbon source at 62.4 °C and pH 7.7 with the maximum oil degradation capability of 91.3 ±â€¯5%. Critical micelle concentration value of crude biosurfactant was found to be 40 mg/L with high emulsification activity of 72.45 ±â€¯0.85%. The produced biosurfactant was identified as lipopeptide (Surfactin) and characterized using various analytical techniques to establish its suitability for microbial enhanced oil recovery.

Synthesis, characterization and in vitro analysis of α-Fe2O3-GdFeO3 biphasic materials as therapeutic agent for magnetic hyperthermia applications.

The use of gadolinium orthoferrite for biomedical application like as contrast agents for magnetic resonance imaging (MRI) has been found to be very promising due to its fascinating properties. The present study focuses on the determination of the effect of the gadolinium concentration in the formation biphasic α-Fe2O3-GdFeO3 for hyperthermia applications. An in-situ sol-gel technique was adopted for the synthesis of biphasic orthoferrites with four different gadolinium concentrations. The XRD analysis confirmed the formation of gadolinium orthoferrites after heat treatment at 1000 °C, 1100 °C, and 1200 °C. The presence of α-Fe2O3 in trace amounts was observed in the materials with low gadolinium concentrations. VSM (Vibrating-sample magnetometer) analysis was performed to ensure the magnetic properties of the materials, which were found to be weakly ferromagnetic. The biocompatibility of the materials was investigated through MTT assay and no cytotoxic effect was observed. The assessment of heating ability of the materials was performed under an alternating magnetic field using an induction heating instrument and all the samples showed temperature rise in the range of hyperthermia temperature with a maximum temperature of 55.71 °C in 6 min. The heating experiments at 44 °C in the absence of samples established the vulnerability of cancer cells as compared to normal cells.