Jayesh R. Bellare

Synthesis of silver nanoparticles using Dioscorea bulbifera tuber extract and evaluation of its synergistic potential in combination with antimicrobial agents.

Background Development of an environmentally benign process for the synthesis of silver nanomaterials is an important aspect of current nanotechnology research. Among the 600 species of the genus Dioscorea, Dioscorea bulbifera has profound therapeutic applications due to its unique phytochemistry. In this paper, we report on the rapid synthesis of silver nanoparticles by reduction of aqueous Ag+ ions using D. bulbifera tuber extract. Methods and results Phytochemical analysis revealed that D. bulbifera tuber extract is rich in flavonoid, phenolics, reducing sugars, starch, diosgenin, ascorbic acid, and citric acid. The biosynthesis process was quite fast, and silver nanoparticles were formed within 5 hours. Ultraviolet-visible absorption spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, energy dispersive spectroscopy, and x-ray diffraction confirmed reduction of the Ag+ ions. Varied morphology of the bioreduced silver nanoparticles included spheres, triangles, and hexagons. Optimization studies revealed that the maximum rate of synthesis could be achieved with 0.7 mM AgNO3 solution at 50°C in 5 hours. The resulting silver nanoparticles were found to possess potent antibacterial activity against both Gram-negative and Gram-positive bacteria. Beta-lactam (piperacillin) and macrolide (eryth-romycin) antibiotics showed a 3.6-fold and 3-fold increase, respectively, in combination with silver nanoparticles selectively against multidrug-resistant Acinetobacter baumannii. Notable synergy was seen between silver nanoparticles and chloramphenicol or vancomycin against Pseudomonas aeruginosa, and was supported by a 4.9-fold and 4.2-fold increase in zone diameter, respectively. Similarly, we found a maximum 11.8-fold increase in zone diameter of streptomycin when combined with silver nanoparticles against E. coli, providing strong evidence for the synergistic action of a combination of antibiotics and silver nanoparticles. Conclusion This is the first report on the synthesis of silver nanoparticles using D. bulbifera tuber extract followed by an estimation of its synergistic potential for enhancement of the antibacterial activity of broad spectrum antimicrobial agents.

Extreme homeopathic dilutions retain starting materials: A nanoparticulate perspective

Homeopathy is controversial because medicines in high potencies such as 30c and 200c involve huge dilution factors (10⁶⁰ and 10⁴⁰⁰ respectively) which are many orders of magnitude greater than Avogadros number, so that theoretically there should be no measurable remnants of the starting materials. No hypothesis which predicts the retention of properties of starting materials has been proposed nor has any physical entity been shown to exist in these high potency medicines. Using market samples of metal-derived medicines from reputable manufacturers, we have demonstrated for the first time by Transmission Electron Microscopy (TEM), electron diffraction and chemical analysis by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES), the presence of physical entities in these extreme dilutions, in the form of nanoparticles of the starting metals and their aggregates.

Gnidia glauca flower extract mediated synthesis of gold nanoparticles and evaluation of its chemocatalytic potential.

BackgroundNovel approaches for synthesis of gold nanoparticles (AuNPs) are of utmost importance owing to its immense applications in diverse fields including catalysis, optics, medical diagnostics and therapeutics. We report on synthesis of AuNPs using Gnidia glauca flower extract (GGFE), its detailed characterization and evaluation of its chemocatalytic potential.ResultsSynthesis of AuNPs using GGFE was monitored by UV-Vis spectroscopy and was found to be rapid that completed within 20 min. The concentration of chloroauric acid and temperature was optimized to be 0.7 mM and 50°C respectively. Bioreduced nanoparticles varied in morphology from nanotriangles to nanohexagons majority being spherical. AuNPs were characterized employing transmission electron microscopy, high resolution transmission electron microscopy. Confirmation of elemental gold was carried out by elemental mapping in scanning transmission electron microscopic mode, energy dispersive spectroscopy and X-ray diffraction studies. Spherical particles of size ~10 nm were found in majority. However, particles of larger dimensions were in range between 50-150 nm. The bioreduced AuNPs exhibited remarkable catalytic properties in a reduction reaction of 4-nitrophenol to 4-aminophenol by NaBH4 in aqueous phase.ConclusionThe elaborate experimental evidences support that GGFE can provide an environmentally benign rapid route for synthesis of AuNPs that can be applied for various purposes. Biogenic AuNPs synthesized using GGFE exhibited excellent chemocatalytic potential.

Synthesis of gold nanoanisotrops using dioscorea bulbifera tuber extract

Biosynthesis of metal nanoparticles employing plant extracts and thereby development of an environmentally benign process is an important branch of nanotechnology. Here, the synthesis of gold nanoparticles using Dioscorea bulbifera tuber extract (DBTE) as the reducing agent is reported. Field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDX), X-ray diffraction (XRD), and UV-visible absorption spectroscopy confirmed the reduction of gold ions to AuNPs. The anisotropic nanoparticles consist of a mixture of gold nanotriangles, nanoprisms, nanotrapezoid, and spheres. The kinetics of particle formation was time dependent and was enhanced by the increase of temperature from 6° to 50°, the optimum being 50°. The optimum concentration of chloroauric acid was found to be 1mM. Complete reduction of the metal ions within 5 hours by DBTE highlights the development of a novel ecofriendly route of biological synthesis of gold nanoparticles. This is the first paper on synthesis of gold nanoparticles using DBTE.

Structural evolution in catanionic mixtures of cetylpyridinium chloride and sodium deoxycholate

Sodium deoxycholate (NaDC) is a water soluble bile salt commonly used in applications ranging from cell lysis, liposome preparation and isolation of membrane proteins. We present the microstructural evolution in aqueous mixtures of biocompatible cationic surfactant cetylpyridinium chloride (CPC) and bile salt NaDC using dynamic light scattering (DLS), small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS). When the total concentration of the mixture (CT) is less than 370 mM, associative phase separation occurs, near the equimolar ratio, which vanishes at high concentrations (>370 mM). The associative phase separation observed at low CT has been explained on the basis of competition between electrostatic attraction and entropy of mixing of the components. Pure CPC micelles undergo shape transition from prolate to oblate, as the concentration increases from 50 mM to 400 mM. Small addition of NaDC to 400 mM of CPC leads to marginal size change in the oblate micelles. On the other hand, pure NaDC micelles are prolate ellipsoids for which the micellar size increases by incorporation of CPC. The observed structural transition is explained in terms of the electrostatic binding of bile salts to cationic surfactants and the incorporation of the steroidal skeleton in the bile salt at the micelle core-head group interface. Microstructure evolution in catanionic mixtures comprising biocompatible surfactants offers potential pharmaceutical applications.

Size dependent optical properties of the CdSe-CdS core-shell quantum dots in the strong confinement regime

We have investigated the third-order optical nonlinearity in CdSe and CdSe-CdS core-shell quantum dots with particle sizes in the range 4.4–5.2 nm by the z-scan technique. Optical absorption and fluorescence properties show quantum confinement effect and the fluorescence peak is shifted when the diameter of the core-shell quantum dots becomes large. Their nonlinear absorption and nonlinear refraction were observed with nanosecond laser radiation of 532-nm wavelength. At an excitation irradiance of 392 MW/cm2, the CdSe-CdS core-shell quantum dots exhibit a reverse saturation and a negative nonlinear refractive index indicating a clear nonlinear behavior. The introduction of CdS shell around CdSe core gives large third-order nonlinearity and third-order optical susceptibility decreases with increasing particle core size in the case of core-shell quantum dots within the range of our investigations. The third-order susceptibility of these quantum dots vary from 3.39 × 10−11 to 5.77 × 10−11 esu. The optical li...

Interaction of contraceptive antimicrobial peptide nisin with target cell membranes: implications for use as vaginal microbicide

BACKGROUND Nisin, a naturally occurring antimicrobial peptide (AMP), is currently the focus of clinical trials as an intravaginal microbicide. Therefore its mechanism of interaction with various cell membranes was studied. STUDY DESIGN Flow cytometry was used for quantitative estimation of membrane damage by nisin which was further determined by scanning electron microscopy (SEM). Affinity of nisin for different unilamellar liposome vesicles was determined spectroflurometrically and confirmed using laser scanning confocal microscopy (LSCM). RESULTS Propidium iodide (PI) staining by flow cytometry exhibited selective membrane permeabilizing effect of nisin on sperm and bacterial membranes which correlated with ultrastructural changes. In vitro interaction of nisin with liposome model vesicles revealed significant leakage of calcein from liposomes composed of phosphatidylcholine/phosphatidylglycerol (POPC/POPG) (e.g., bacteria) and phosphatidylcholine/phosphatidylserine (POPC/POPS) (e.g., spermatozoa) as compared to phosphatidylcholine/phosphatidylethanolamine (POPC/POPE) vesicles (e.g., red blood corpuscles). LSCM results were in complete agreement with cell membrane affinity studies. CONCLUSION This unique property of nisin can be exploited in the development of a safe and effective vaginal microbicide for the prevention of sexually transmitted infections/acquired immunodeficiency syndrome (STIs/AIDS) and unplanned pregnancies.

Manufacture of gem quality diamonds: a review

Abstract Gem quality diamonds have been grown using high temperature, high pressure processes like the solvent catalyst method and the temperature gradient method. This review with 64 references focuses on the thermodynamics, kinetics of the growth processes and the apparatus used to grow diamonds. Gem quality diamonds can be synthesized by the high pressure, high temperature process, either by the solvent catalyst method or the reconstitution technique. The Hall belt apparatus and the toroid anvil are the commonly used equipment to generate high pressures. In the high pressure, high temperature processes a catalyst is essential for synthesis. The commonly used catalysts are Fe, Co and Ni whereas recently hydroxides and carbonates have also been used to synthesize diamond. Surface chemistry plays an important role in determining the quality of the crystal. If the carbon flux to the nucleating diamond exceeds a certain limit, graphite nucleates instead of diamond. Temperature, pressure and impurities like nitrogen and boron also affect the quality and growth rates of the synthesized diamond. High growth rates have also been observed if substantial amount of paramagnetic nitrogen is dispersed in the reaction bath. Recent developments of growing diamond by chemical vapour deposition techniques like microwave plasma and hot filament technique have been reviewed. Non-destructive, optical methods to characterize diamonds have been briefly described. ©

Influence of carboxymethyl chitin on stability and biocompatibility of 3D nanohydroxyapatite/gelatin/carboxymethyl chitin composite for bone tissue engineering†

A novel three-dimensional (3D) scaffold has been developed from the unique combination of nanohydroxyapatite/gelatin/carboxymethyl chitin (n-HA/gel/CMC) for bone tissue engineering by using the solvent-casting method combined with vapor-phase crosslinking and freeze-drying. The surface morphology and physiochemical properties of the scaffold were investigated by dissolvability test, infrared absorption spectra (IR), X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), mechanical testing, and soaking in simulated body fluid (SBF). An optimized (composition and processing parameters) ratio of n-HA:gel:CMC (1:2:1), exhibited ideal porous structure with regular interconnected pores (75-250 μm) and higher mechanical strength. Result suggested that the divalent (Ca(++)), carboxyl (COO(-)), amino (NH4(+)), and phosphate (PO4(3-)) groups created favorable ionic interactions which facilitated structural stability and integrity of the composite scaffold. The SBF soaking experiment confirmed the apatite nucleation ability, induced by CMC incorporation. Furthermore, hemocompatibility (hemolysis, platelet adhesion, and protein adsorption) and biocompatibility with MG63 osteoblast cells (MTT assay, cell morphology, and confocal studies from within the 3D scaffold) indicated that the structural and dimensional stability of composite scaffold provided an optimal mechanosensory environment for enhancement of cell adhesion, proliferation, and network formation. The n-HA/gel/CMC composite, therefore, may serve as a promising composite scaffold for guided bone regeneration.

Synthesis and characterization of low molecular weight cut off ultrafiltration membranes from cellulose propionate polymer

This paper describes the synthesis and characterization of low molecular weight cut-off ultrafiltration (UF) membranes from cellulose propionate (CP) polymer using dimethyl acetamide solvent. The casting conditions are studied with reference to changes in the nature of additive and additive to solvent ratio. The membranes are characterized in terms of product permeation rate, solute retention for different electrolytes, as a function of feed concentration and pressure. The retention of different dyes are also included. Molecular weight cut off profiles using polyethylene glycol solutes of different molecular weights are presented. The separation behaviour of oil-water and milk protein systems are presented in order to highlight the fouling resistance of CP membranes.