Showing papers by "Ashok M. Raichur published in 2014"

In Vivo Genotoxicity Assessment of Titanium Dioxide Nanoparticles by Allium cepa Root Tip Assay at High Exposure Concentrations

Abstract: The industrial production and commercial applications of titanium dioxide nanoparticles have increased considerably in recent times, which has increased the probability of environmental contamination with these agents and their adverse effects on living systems. This study was designed to assess the genotoxicity potential of TiO2 NPs at high exposure concentrations, its bio-uptake, and the oxidative stress it generated, a recognised cause of genotoxicity. Allium cepa root tips were treated with TiO2 NP dispersions at four different concentrations (12.5, 25, 50, 100 µg/mL). A dose dependant decrease in the mitotic index (69 to 21) and an increase in the number of distinctive chromosomal aberrations were observed. Optical, fluorescence and confocal laser scanning microscopy revealed chromosomal aberrations, including chromosomal breaks and sticky, multipolar, and laggard chromosomes, and micronucleus formation. The chromosomal aberrations and DNA damage were also validated by the comet assay. The bio-uptake of TiO2 in particulate form was the key cause of reactive oxygen species generation, which in turn was probably the cause of the DNA aberrations and genotoxicity observed in this study.

Tailor-Made Hollow Silver Nanoparticle Cages Assembled with Silver Nanoparticles: An Efficient Catalyst for Epoxidation

Abstract: A novel approach toward the synthesis of hollow silver nanoparticle (NP) cages built with building blocks of silver NPs by layer-by-layer (LbL) assembly is demonstrated. The size of the NP cage depends on the size of template used for the LbL assembly. The microcages showed a uniform distribution of spherical silver nanoparticles with an average diameter of 20 ± 5 nm, which increased to 40 ± 5 nm when the AgNO3 concentration was increased from 25 to 50 mM. Heat treatment of the polyelectrolyte capsules at 80 °C near their pKa values yielded intact nano/micro cages. These cages produced a higher conversion for the epoxidation of olefins and maintained their catalytic activity even after four successive uses. The nanocages exhibited unique and attractive characteristics for metal catalytic systems, thus offering the scope for further development as heterogeneous catalysts.

Protamine‐Capped Mesoporous Silica Nanoparticles for Biologically Triggered Drug Release

Abstract: The fabrication of a mesoporous silica nanoparticle (MSN)-protamine hybrid system (MSN-PRM) is reported that selectively releases drugs in the presence of specific enzyme triggers present in the proximity of cancer cells. The enzyme trigger involved is a protease called trypsin, which is overexpressed in certain specific pathological conditions, such as inflammation and cancer. Overexpression of trypsin is known to be associated with invasion, metastasis, and growth in several cancers, such as leukemia, colon cancer, and colorectal cancer. The current system (MSN-PRM) consists of an MSN support in which mesopores are capped with an FDA-approved peptide drug protamine, which effectively blocks the outward diffusion of the drug molecules from the mesopores of the MSNs. On exposure to the enzyme trigger, the protamine cap disintegrates, opening up the molecular gates and releasing the entrapped drug molecules. The system exhibits minimal premature release in the absence of the trigger and selectively releases the encapsulated drugs in the presence of the proteases secreted by colorectal cancer cells. The ability of the MSN-PRM particles to deliver anticancer drugs to colorectal cancer cells has also been demonstrated. The hydrophobic drug is released into cancer cells subsequent to disintegration of the protamine cap, resulting in cell death. Drug-induced cell death in colorectal cancer cells is significantly enhanced when the hydrophobic drug that is known to degrade in aqueous environments is encapsulated in the MSN-PRM system in comparison to the free drug (P < 0.05). The system, which shows good biocompatibility and selective drug release, is a promising platform for cancer specific drug delivery.

Dual enzyme responsive and targeted nanocapsules for intracellular delivery of anticancer agents

Abstract: We report the fabrication of dual enzyme responsive hollow nanocapsules which can be targeted to deliver anticancer agents specifically inside cancer cells. The enzyme responsive elements, integrated in the nanocapsule walls, undergo degradation in the presence of either trypsin or hyaluronidase leading to the release of encapsulated drug molecules. These nanocapsules, which were crosslinked and functionalised with folic acid, showed minimal drug leakage when kept in pH 7.4 PBS buffer, but released the drug molecules at a rapid rate in the presence of either one of the triggering enzymes. Studies on cellular interactions of these nanocapsules revealed that doxorubicin loaded nanocapsules were taken up by cervical cancer cells via folic acid receptor medicated endocytosis. Interestingly the nanocapsules were able to disintegrate inside the cancer cells and release doxorubicin which then migrated into the nucleus to induce cell death. This study indicates that these nanocapsules fabricated from biopolymers can serve as an excellent platform for targeted intracellular drug delivery to cancer cells.

Lipid coated mesoporous silica nanoparticles as an oral delivery system for targeting and treatment of intravacuolar Salmonella infections

Abstract: Lipid coated mesoporous silica nanoparticle (L-MSN) were synthesized for oral delivery of ciprofloxacin for intracellular elimination of Salmonella pathogen. The particle size was found to be between 50-100 nm with a lipid coat of approximately 5 nm thickness. The lipid coating was achieved by sonication of liposomes with the MSN particles and evaluated by CLSMand FTIR studies. The L-MSN particles exhibited lower cytotoxicity compared to bare MSN particles. Ciprofloxacin, a fluoroquinolone antibiotic, loaded into the L-MSN particles showed enhanced antibacterial activity against free drug in in vitro assays. The lipid coat was found to aid in intravacuolar targeting of the drug cargo as observed by confocal microscopy studies. We also observed that a lower dose of antibiotic was sufficient to clear the pathogen from mice and increase their survivability using the L-MSN oral delivery system.

Sunlight Irradiation Induced Green Synthesis of Stable Silver Nanoparticles Using Citrus limon Extract

Abstract: In the present study, silver nanoparticles were rapidly synthesized photochemically by treating silver ions with lemon (Citrus limon) extract utilizing solar radiation. The effect of time period of the day on reaction rate and nanoparticle formation was investigated in details. In the standardized process, 10 -2 M silver nitrate solution was interacted for 20 min with lemon juice (2 % citric acid and 0.5 % ascorbic acid concentration) in the ratio of 1:4 (vol:vol) in the presence of sunlight. Silver nanoparticles below 50 nm with spherical and spheroidal shape were observed under electron microscopic analysis. The authors have hereby developed an energy efficient bio-based synthesis process which produces silver nanoparticles rapidly.

Effect of film thickness and annealing on optical properties of TiO2 thin films and electrical characterization of MOS capacitors

Abstract: Titanium dioxide (TiO2) thin films were deposited on glass and silicon (100) substrates by the sol–gel method. The influence of film thickness and annealing temperature on optical transmittance/reflectance of TiO2 films was studied. TiO2 films were used to fabricate metal–oxide–semiconductor capacitors. The capacitance–voltage (C–V), dissipation–voltage (D–V) and current–voltage (I–V) characteristics were studied at different annealing temperatures and the dielectric constant, current density and resistivity were estimated. The loss tangent (dissipation) increased with increase of annealing temperature.

Influence of Temperature and Doping on Photo-Catalytic Activity of TiO 2 Films

Abstract: Titanium dioxide (TiO 2) thin films were synthesized by the sol-gel method . The titanium (IV) iso- propoxide and ethanol were used as precursor of TiO 2 and solvent, respectively. The TiO 2 sol was spin coated on glass substrates and pre-heated at 50 o C for 15 min. The films were annealed at different temperatures for two hours in ambient air to obtain TiO 2 films. The same methodology was followed with the doping of different wt. % of tin (Sn) in TiO 2 sol to prepare Sn-TiO 2 films. The crystal structure of the TiO 2 films was analyzed by x-ray diffraction (XRD) patterns and found to be anatase phase after annealing at 300 o C and higher temperatures. The films were tested for photo-catalytic activity for the degradation of methyl orange dye in the presenc e of UV light. The photo-catalytic property of the TiO 2 films varied with the annealing temperature and th e doping of Sn.