Jyoti Prasad Saikia

Nickel oxide nanoparticles: A novel antioxidant

We investigated a novel inorganic (nickel oxide) nanoparticles as a potential antioxidant in the biosystems. The particles were synthesized using self-propagating high-temperature synthesis (SHS) method at 650 degrees C. The antioxidant property of the nickel oxide particles was investigated in an in vitro system, using modified DPPH method for insoluble solid materials.

Biocompatible novel starch/polyaniline composites: Characterization, anti-cytotoxicity and antioxidant activity

Starch/polyaniline composites have been synthesized using oxidative polymerization of polyaniline in an aqueous dispersion of starch isolated from Colocasia esculenta corm. Scanning electron micrographs reveals the growth of polyaniline over the surface of the starch granules. DPPH scavenging and haemolysis prevention assay have been performed to estimate the antioxidant activity and cytotoxicity of the composites. Formation of new properties of the composites as compared to starch and poloyaniline was evident from the X-ray diffraction analysis (XRD). Characterization done using UV-Vis, FTIR and DSC analysis provide evidence of composite formation. Composite possesses antioxidant nature which increases with the concentration of polyaniline. The haemolysis prevention activity of these novel composite materials is found to increase as compared to the pure polyaniline with minor compromise in the antioxidant activity. The materials show tremendous potential for biomedical applications.

Biocompatible epoxy modified bio-based polyurethane nanocomposites: Mechanical property, cytotoxicity and biodegradation

Epoxy modified Mesua ferrea L. seed oil (MFLSO) based polyurethane nanocomposites with different weight % of clay loadings (1%, 2.5% and 5%) have been evaluated as biocompatible materials. The nanocomposites were prepared by ex situ solution technique under high mechanical shearing and ultrasonication at room temperature. The partially exfoliated nanocomposites were characterized by Fourier transform infra-red (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The mechanical properties such as tensile strength and scratch hardness were improved 2 and 5 times, respectively by nanocomposites formation. Even the impact resistance improved a little. The thermostability of the nanocomposites was enhanced by about 40 degrees C. Biodegradation study confirmed 5-10 fold increase in biodegradation rate for the nanocomposites compared to the pristine polymers. All the nanocomposites showed non-cytotoxicity as evident from RBC hemolysis inhibition observed in anti-hemolytic assay carried over the sterilized films. The study reveals that the epoxy modified MFLSO based polyurethane nanocomposites deserve the potential to be applicable as biomaterials.

Antioxidant activity and haemolysis prevention efficiency of polyaniline nanofibers.

Polyaniline (PAni) nanofibers have been synthesized by interfacial polymerization using hydrochloric acid (HCl) and camphor sulfonic acid (CSA) as dopants. The powder x-ray diffraction pattern of bulk polyaniline reveals ES I structure and has been indexed in a pseudo-orthorhombic lattice. The broadening of (110) reflection in the nanofiber samples has been analysed in terms of domain length and strain using a convolution method employing a Voigt function. The increase in d spacing for the (110) reflection in HCl-doped PAni nanofibers have been assigned to the change in structural conformation due to the increase in the tilt angle of the polymer chain, which is also evident from microRaman spectra. UV-vis spectra of the PAni nanofibers exhibit a remarkable blueshift in the absorption bands attributed to pi-pi* and pi-polaron band transitions indicating a reduction in particle size, which is also observed in TEM micrographs. The antioxidant activity of the polyaniline nanofiber samples has been investigated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay by employing UV-visible spectroscopy. It has also been observed that polyaniline nanofibers are able to protect the haemolysis of red blood cells (RBCs) from cytotoxic agents, namely H(2)O(2). The observed enhancement in the antioxidant and haemolysis prevention activity of the PAni nanofibers as compared to bulk has been attributed to the reduction in particle size and changes in structural conformation, as evident from TEM, XRD and microRaman spectroscopy.

A novel ‘green’ synthesis of colloidal silver nanoparticles (SNP) using Dillenia indica fruit extract

In the present research we have defined a novel green method of silver nanoparticles synthesis using Dillenia indica fruit extract. D. indica is an edible fruit widely distributed in the foothills of Himalayas and known for its antioxidant and further predicted for cancer preventive potency. The maximum absorbance of the colloidal silver nanoparticle solution was observed at 421 nm when examined with UV-vis spectrophotometer.

Rhamnolipid (RL) from Pseudomonas aeruginosa OBP1: A novel chemotaxis and antibacterial agent

In the present study, the interaction of rhamnolipid produced by Pseudomonas aeruginosa OBP1 with the cell surfaces of Staphylococcus aureus (MTCC 3160) and Klebsiella pneumoniae (MTCC 618) were studied. Rhamnolipid concentration below critical micelle concentration (CMC) did not exhibit significant antibacterial activity. However, on increasing rhamnolipid concentration beyond CMC a prominent antibacterial activity was observed. The results demonstrated different degree of rhamnolipid interaction with both the bacteria. This might be due to the changes in their cell wall composition. The antibacterial activity determined by minimum inhibitory concentration (MIC). The antibacterial activity is prominent within 30 min of incubation. The antibacterial property of rhamnolipid was effective in all tested pH levels (5-9). The rhamnolipid was effective in almost all tested pH levels and showed better chemoattractant property against both the tested bacteria in comparison to glucose. The increase in the membrane permeability was evidenced by increase in the release of protein, enhancement in cell surface hydrophobicity and raises in the retention of crystal violet dye. Further, leakage of 260 nm absorbing intracellular materials, fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis confirmed the disruptive action of rhamnolipid. The above evidences support the idea that rhamnolipid significantly alters the cell membrane/envelop that leads to cell damage and enhances membrane permeability. Such activity of rhamnolipid could be used as an additive in the formulation of antibiotic and other antimicrobial agents for enhancing the effectiveness of chemotherapeutics.

‘Poly(ethylene glycol)-magnetic nanoparticles-curcumin’ trio: Directed morphogenesis and synergistic free-radical scavenging

Research on curcumin (polyphenol derived from the rhizome of herb Curcuma longa) has occupied a unique niche owing to its distinctive properties, unique molecular architecture and multi-potent efficacies, particularly in the bio-medical domain with recent interest in material science. In the present study, conjugation of curcumin onto biocompatible poly(ethylene glycol)--templated magnetic iron oxide nanoparticles (MNP) (2-5 nm), prepared through a simple wet chemical route is reported along with modulation of the activity of the partners. Statistical optimization, using response surface methodology, of sonication parameters (8 min, 0.4 cycle and 60% amplitude) for maximal curcumin loading (86%), has shown major morphology directing effect generating triads, tetrads, amongst others and chain-like arrangement (TEM imaging) of the bio-conjugated nanoparticles (80-90 nm). Intonation of the magnetometric parameters of the PEG assisted MNPs on bioconjugation was also evident. The synergistic potency of the partners, the polymer templated iron oxide nanoparticles and curcumin, was unmasked during scavenging of diphenyl picryl hydrazyl (DPPH). The system represents an architecturally appealing, magnetically responsive bio-conjugated system possessing synergistic participation of the partners, with prospective applications in medical domain.

Enhancing the stability of colloidal silver nanoparticles using polyhydroxyalkanoates (PHA) from Bacillus circulans (MTCC 8167) isolated from crude oil contaminated soil.

Polyhydroxyalkanoate (PHA) was produced by growing Bacillus circulans (MTCC 8167) in the specific detection medium. The identification of the polymer as PHA was confirmed by fluorescence microscopy. The PHA was purified and characterized using FT-IR. The silver nanoparticles (SNP) were synthesized from AgNO3 in the dispersed colloids of PHA (0.085%) using NaBH4 (sodium borohydrate as reducing agent). The stability was tested using wave length scanning with a UV-Vis spectrophotometer and finally with transmission electron microscopy. The PHA stabilized solution was found to be stable for 30 days as against the low stability of silver nanoparticles (SNP) solution alone.

Bio-plastic (P-3HB-co-3HV) from Bacillus circulans (MTCC 8167) and its biodegradation.

Polyhydroxyalkanoates (PHAs) are naturally occurring polyesters synthesized by bacteria for carbon and energy storage and it has commercial potential as bioplastic. The bacterial species Bacillus circulans MTCC 8167, isolated from crude oil contaminated soil, can efficiently produce medium chain length polyhydroxyalkanoates (P-3HB-co-3HV) from cheap carbon sources like dextrose. The molecular mass of P-3HB-co-3HV was reported as 5.1×10(4)Da with polydispersity index of 1.21 by gel permeation chromatography. In the present investigation different bacteria and fungi species were used for testing the biodegradability of the extracted polymer. The FTIR spectra of the biodegraded PHBV film showed a decrease in the peak from 1735 cm(-1) (untreated film) to 1675 cm(-1), and disappearance of a peak present in the control at 2922 cm(-1) indicating the breakdown of ester (>C=O) or O-R group and -C=H bond, respectively. From biodegradability testing, the tested microorganisms were found to have decisive contribution to the biodegradation of P-3HB-co-3HV polymer.

Swift heavy ion irradiation induced enhancement in the antioxidant activity and biocompatibility of polyaniline nanofibers

Polyaniline (PAni) nanofibers doped with HCl and CSA have been irradiated with 90 MeV O(7+) ions with fluence of 3 x 10(10), 3 x 10(11) and 1 x 10(12) ions cm(-2). TEM micrographs show a decrease in the fiber diameter with increasing irradiation fluence, which has been explained on the basis of the Coulomb explosion model. XRD analysis reveals a decrease in the crystalline domain length and an increase in the strain. The increase in d-spacing for the (100) reflection with increasing irradiation fluence is ascribed to the increase in the tilt angle of the polymer chain, which is also evident from micro-Raman spectra. UV-vis spectra of the PAni nanofibers exhibit blue-shift in the absorption bands attributed to pi-pi* band transitions indicating a reduction in particle size after SHI irradiation; as also observed in TEM micrographs. Micro-Raman spectra also reveal a transition from the benzenoid to quinoid structures in the PAni chain as the fluence is increased. Although the quinoid unit has no hydrogen for DPPH scavenging, the antioxidant activity of PAni nanofibers is found to increase with increasing fluence. This has been attributed to the availability of more reaction sites as a result of fragmentation of the PAni nanofibers which compensates for the benzenoid to quinoid transition after irradiation. The biocompatibility of the PAni nanofibers is also found to increase with increasing irradiation fluence, indicating the possibility of employing swift heavy ion irradiation as an effective technique in order to modify conducting polymer nanostructures for biomedical applications.