Hari C. Bajaj

Montmorillonite as a drug delivery system: Intercalation and in vitro release of timolol maleate

The need for safe, therapeutically effective, and patient-compliant drug delivery systems continuously leads researchers to design novel tools and strategies. Clay minerals play a very crucial role in modulating drug delivery. This work examines the advantageous effect of clay mineral as drug carrier for timolol maleate (TM), a nonselective beta-adrenergic blocking agent. The intercalation of TM into the interlayer of montmorillonite (MMT) at different pH and initial concentration is demonstrated. MMT-TM hybrid was characterized by X-ray diffraction (XRD), Fourier transformed infrared (FT-IR), and thermal analysis (TG-DTA). TM was successfully intercalated into the interlayer of MMT, and in vitro release properties of the intercalated TM have been investigated in simulated gastric fluid (pH 1.2) and simulated intestinal fluid (pH 7.4) at 37+/-0.5 degrees C. Controlled release of TM from MMT-TM hybrid has been observed during in vitro release experiments.

Nanoclays for polymer nanocomposites, paints, inks, greases and cosmetics formulations, drug delivery vehicle and waste water treatment

An overview of nanoclays or organically modified layered silicates (organoclays) is presented with emphasis placed on the use of nanoclays as the reinforcement phase in polymer matrices for preparation of polymer/layered silicates nanocomposites, rheological modifier for paints, inks and greases, drug delivery vehicle for controlled release of therapeutic agents, and nanoclays for industrial waste water as well as potable water treatment to make further step into green environment. A little amount of nanoclay can alter the entire properties of polymers, paints, inks and greases to a great extent by dispersing 1nm thick layered silicate throughout the matrices. The flexibility of interlayer spacing of layered silicates accommodates therapeutic agents which can later on be released to damaged cell. Because the release of drugs in drug-intercalated layered materials is controllable, these new materials have a great potential as a delivery host in the pharmaceutical field. The problem of clean water can be solved by treating industrial and municipal waste water with organoclays in combination with other sorbents like activated carbon and alum. Organoclays have proven to be superior to any other water treatment technology in applications where the water to be treated contains substantial amounts of oil and grease or humic acid.

Adsorption of an anionic dye from aqueous medium by organoclays: equilibrium modeling, kinetic and thermodynamic exploration

Adsorption of an anionic dye, remazole brilliant blue R (RBBR) from aqueous solution, on organically modified attapulgite (ATP) and bentonite (BNT) clays was investigated. Beneficiated attapulgite and bentonite clay samples were modified by the cationic surfactant cetyltrimethylammoniumbromide (CTAB) by the ion exchange method. The efficiency of these adsorbents for the uptake of RBBR was examined by a series of adsorption isotherms using a batch technique at three different temperatures. A modified Freundlich equation has been proposed to describe the isotherms and compared with Langmuir, Freundlich and Redlich–Peterson (RP) models. Predicated values of RBBR adsorbed on modified clay using Freundlich, modified Freundlich, and RP models were identical along with the normalized standard deviation for all three models. These values were lower than those of Langmuir model. Values of r2 for RP and modified Freundlich were found to be identical and better than that of Langmuir for all the isotherms. Adsorption of RBBR followed a pseudo second order kinetic model. Negative values of free energy change, ΔG indicated spontaneity of the adsorption of RBBR on both of organoclays. An increase in adsorption of RBBR with an increase in temperature may be attributed to activated adsorption and hence an endothermic process. This was further supported by positive values of heat of adsorption, ΔH. The adsorption capacity of modified attapulgite is lower than that of modified bentonite. However, considering the requirement of CTAB for modification of the clay, attapulgite is the more economical adsorbent than modified bentonite.

Layered bionanocomposites as carrier for procainamide

The study deals with the intercalation of procainamide hydrochloride (PA), an antiarrythmia drug in montmorillonite (MMT), as a new drug delivery device. Optimum intercalation of PA molecules within the interlayer space of MMT was achieved by means of different reaction conditions. Intercalation of PA in the MMT galleries was conformed by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), and thermal analysis (DSC). In order to retard the quantity of drug release in the gastric environment, the prepared PA-MMT composite was compounded with alginate (AL), and further coated with chitosan (CS). The surface morphology of the PA-MMT-AL and PA-MMT-AL-CS nanocomposites beads was analyzed by scanning electron microscope (SEM). The in vitro release experiments revealed that AL and CS were able to retard the drug release in gastric environments, and release the drug in the intestinal environments with a controlled manner. The release profiles of PA from composites were best fitted in Higuchi kinetic model, and Korsmeyer-Peppas model suggested diffusion controlled release mechanism.

Preferential adsorption behavior of methylene blue dye onto surface hydroxyl group enriched TiO2 nanotube and its photocatalytic regeneration.

The present manuscript focus on the synthesis of surface hydroxyl group enriched titanium dioxide nanotube (TNT) by hydrothermal method for preferential adsorption of methylene blue (MB) dye. The mixture of methylene blue (MB) and rhodamine B (RhB) dye was used to study the preferential adsorption nature of TNT. The synthesized TNT were characterized by various techniques such as powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption, and ammonia-temperature programmed desorption (NH3-TPD) analysis. Result demonstrated that enhancement in the surface area of TNT and higher number of hydroxyl group on the surface of TNT. In the binary mixture, the adsorption of MB dye was 12.9 times higher as compared to RhB dye, which clearly indicated the preferential adsorption of MB dye on TNT surface. The preferential interaction of MB on TNT is due to the electrostatic interaction between the cationic MB and negatively charged TNT surface. The preferential adsorption of MB dye was studied by applying Langmuir, Freundlich and Sips isotherm; pseudo-first and second-order kinetic model. Furthermore, the regeneration of dye adsorbed TNT was carried out by eco-friendly photocatalytic process under the irradiation of ultraviolet light.

Heterogeneous Chiral Copper Complexes of Amino Alcohol for Asymmetric Nitroaldol Reaction

Chiral amino alcohols supported on mesoporous silicas were synthesized and evaluated as a new class of chiral ligands in copper-catalyzed nitroaldol reaction under heterogeneous and mild reaction conditions. The activity and enantioselectivity of the present catalytic system is immensely influenced by the presence of achiral and chiral bases as an additive. The heterogenized chiral copper(II) complex of amino alcohol was found to be an effective recyclable catalyst for the nitroaldol reaction of different aldehydes such as aromatic, aliphatic, alicyclic, and α-β unsaturated aldehydes to produce nitroaldol products with remarkably high enantioselectivity (≥99%) and yields.

Layered inorganic nanocomposites: a promising carrier for 5-fluorouracil (5-FU).

We report here the intercalation of 5-fluorouracil (5-FU), an anticancer drug in interlayer gallery of Na(+) clay (Montmorillonite, MMT), with the assistance of biopolymer (chitosan, CS). The X-ray diffraction patterns, thermal and spectroscopic analyses indicated the drug intercalation into the clay interlayer space in support of CS and stabilized in the longitudinal monolayer by electrostatic interaction. In vitro drug release showed controlled release pattern. The genotoxic effect of drug was in vitro evaluated in human lymphocyte cell culture by comet assay, and results indicated significant reduction in DNA damage when drug was intercalated with clay and formulated in composites. The results of in vitro cell viability assay in cancer cells pointed at decreased toxicity of drug when encapsulated in Na(+)-clay plates than the pristine drug. In vivo pharmacokinetics, biodistribution, hepatotoxicity markers, e.g., SGPT and SGOT, and liver/testicular histology in rats showed plasma/tissue drug levels were within therapeutic window as compared to pristine drug. Therefore, drug-clay hybrid and composites can be of considerable value in chemotherapy of cancer with reduced side effects.

A rapid and green synthetic approach for hierarchically assembled porous ZnO nanoflakes with enhanced catalytic activity

Three dimensionally (3D) assembled hierarchical porous ZnO structures are of key importance for their applications in sensors, lithium-ion batteries, solar cells and in catalysis. Here, the controlled synthesis of 3D hierarchically porous ZnO architectures constructed of two dimensional (2D) nano-sheets through the calcination of a hydrozincite [Zn5(CO3)2(OH)6] intermediate is presented. The intermediate 3D hierarchical hydrozincite has been synthesized by a novel organic surfactant and solvent free aqueous protocol at room temperature using an aqueous solution of ammonium carbonate and laboratory grade bulk ZnO in a short time (20–30 min). The amount of carbonate and the reaction temperature play a crucial role in the formation of the 3D hierarchical morphology and on the basis of the experimental results a probable reaction mechanism is proposed. On calcination, the synthesized 3D hierarchical hydrozincite resulted in ZnO with an almost identical morphology to the parental hydrozincite. On decomposition a porous structure having a surface area of 44 m2 g−1 is obtained. The synthesized hierarchical ZnO morphology exhibits an improved catalytic activity for the synthesis of 5-substituted-1H-tetrazoles with different nitriles and sodium azide than that of nanocrystalline ZnO and bulk ZnO, as well as other developed solid catalysts. The catalyst is easily recyclable without a significant loss in catalytic activity.

Biodegradable gelatin–ciprofloxacin–montmorillonite composite hydrogels for controlled drug release and wound dressing application

This work reports intercalation of a sparingly soluble antibiotic (ciprofloxacin) into layered nanostructure silicate, montmorillonite (MMT) and its reaction with bone derived polypeptide, gelatin that yields three-dimensional composite hydrogel. Drug intercalation results in changes in MMT layered space and drug loaded MMT and gelatin creates 3D morphology with biodegradable composite hydrogels. These changes can be correlated with electrostatic interactions between the drug, MMT and the gelatin polypeptides as confirmed by X-ray diffraction patterns, thermal, spectroscopic analyses, computational modeling and 3D morphology revealed by SEM and TEM analysis. No significant changes in structural and functional properties of drug was found after intercalation in MMT layers and composite hydrogels. In vitro drug release profiles showed controlled release up to 150h. The drug loaded composite hydrogels were tested on lung cancer cells (A549) by MTT assay. The results of in vitro cell migration and proliferation assay were promising as composite hydrogels induced wound healing progression. In vitro biodegradation was studied using proteolytic enzymes (lysozyme and protease K) at physiological conditions. This new approach of drug intercalation into the layered nanostructure silicate by ion-exchange may have significant applications in cost-effective wound dressing biomaterial with antimicrobial property.

Influence of chirality of V(V) Schiff base complexes on DNA, BSA binding and cleavage activity.

New chiral V(V) Schiff base complexes (S)-[VO(OMe)L] and (R)-[VO(OMe)L] were synthesized and characterized by microanalysis, infrared (IR), UV-Visible, Circular dichroism (CD) spectroscopy and single crystal X-ray studies. The interaction of these complexes with calf thymus (CT) DNA and bovine serum albumin (BSA) protein showed chiral expression DNA/protein binding strength. The influence of chirality was also observed in cytotoxicity assay of Hep 2 cells. (R)-[VO(OMe)L] enantiomer exhibited higher binding constant (5 ± 1 × 10(5) M(-1)) as compared to (S)-[VO(OMe)L] (8 ± 1 × 10(4) M(-1)). The fluorescence quenching, thermal melting and viscosity data suggest DNA surface and/or groove binding nature of the complexes and electrophoresis studies also showed greater activity for (R)-[VO(OMe)L] in cleaving DNA and protein as against (S)-[VO(OMe)L].