Ashok M. Dave

Stimulus-Responsive “Smart” Hydrogels as Novel Drug Delivery Systems

ABSTRACT Recently, there has been a great deal of research activity in the development of stimulus-responsive polymeric hydrogels. These hydrogels are responsive to external or internal stimuli and the response can be observed through abrupt changes in the physical nature of the network. This property can be favorable in many drug delivery applications. The external stimuli can be temperature, pH, ionic strength, ultrasonic sound, electric current, etc. A majority of the literature related to the development of stimulus-responsive drug delivery systems deals with temperature-sensitive poly(N-isopropyl acrylamide)(pNIPAAm) and its various derivatives. However, acrylic-based pH-sensitive systems with weakly acidic/basic functional groups have also been widely studied. Quite recently, glucose-sensitive hydrogels that are responsive to glucose concentration have been developed to monitor the release of insulin. The present article provides a brief introduction and recent developments in the area of stimulus-responsive hydrogels, particularly those that respond to temperature and pH, and their applications in drug delivery. *CEPS Communications #4.

Hydrogels as controlled release devices in agriculture

Recently, there has been a great deal of research activity in the development of hydrogels as controlled release devices. The present review provides a brief introduction to various methods of synthesis, properties, types of hydrogels, and cross-linking agents which have been used for the preparation of hydrogels exhibiting suitable properties for agricultural applications.

A Review on Controlled Release of Nitrogen Fertilizers Through Polymeric Membrane Devices

Consequent to the better understanding of various agrochemicals, their functions during the growth cycles of plants and other aspects concerning economics, environment, and so forth, the controlled-release technology has emerged in the areas of fertilizers, herbicides, and pesticides. The present review discusses the technology and applications of controlled-release delivery systems concerning agrochemicals and the related technological advances with some critical suggestions. Emphasis is placed on inexpensive materials, simpler technologies, and statistical evaluation in planning and developing newer system. The interrelationship between technologies for controlled-release and membrane applications is discussed.

Urea-formaldehyde crosslinked starch and guar gum matrices for encapsulation of natural liquid pesticide [Azadirachta Indica A. Juss. (Neem) seed oil] : Swelling and release kinetics

Polymeric granules were prepared by matrix encapsulation containing 20, 35 and 50% (w/w) of natural liquid pesticide viz., Azadirachta Indica A. Juss. (neem) seed oil (NSO) per dry weight of urea formaldehyde crosslinked starch (UF-St), guar gum (UF-GG) and UF-(St + GG) matrices. Results of swelling and cumulative release kinetics are presented at 35°C for these matrices. The static dissolution experiments have been carried out at 35°C for seven days. The percentage cumulative release kinetic data have been analyzed using an empirical equation to study the release pattern of NSO through the polymeric membranes employed. Transport follows the Super Case II mechanism as tested by an empirical equation. It is found that the release of the active ingredient depends upon the type of the matrix and its swelling ability. The percentage loading of NSO with different matrices and their density exerted an influence on the release data. The FTIR results indicated the absence of chemical interactions between the matrices and the NSO. In the majority of cases, entrapment efficiency was generally more than 95% indicating the efficient encapsulation. Furthermore, the experimental results are discussed in terms of the nature and the combined effect of the individual matrices as well as the percentage loading of NSO.

Solubility study of hazardous pesticide (chlorpyrifos) by gas chromatography.

Solubility data of a hazardous pesticide like chlorpyrifos are important in order to determine its residual toxicity from soil and to understand its controlled release characteristics. In this paper, solubility of chlorpyrifos was measured by using gas chromatography in pure water, methanol, and water-methanol mixtures at 298.15, 303. 15, and 308.15K. The results indicate that chlorpyrifos is more soluble in methanol than in water. The solubility of chlorpyrifos in water can be enhanced by adding methanol to water. The effect of temperature on the solubility of chlorpyrifos was observed at higher methanol content in the mixture.

An assessment of solubility profiles of structurally similar hazardous pesticide in water + methanol mixture and co-solvent effect on partition coefficient

This paper reports solubility and partition coefficient data for the structurally similar pesticides, fenvalerate and cypermethrin, measured by UV spectrophotometry in binary mixtures of methanol and water at different temperatures. The solubility of both pesticides is much higher in methanol than in water at all temperatures. Partition coefficients were also measured between water+heptanol immiscible mixtures at 298.15K, and these data show a decrease with increasing composition of methanol in water.

Enhancement of membrane performance with employment of cellulose acetate blend

Abstract The present study reports the comparative assessment of various cellulose acetates and a blend thereof as polymeric materials, their properties in casting solutions and the relative performance of membranes prepared from them. An approach has been made to evaluate these polymers under closely identical conditions. Several prototype physico-chemical interactions possibly involved during the formation of a typical asymmetric membrane are studied. Viscosity evaluations are consistent with those of the cellulose acetates being non-spherical extended macromolecules which acquire flexibility with increasing temperature. The activation energy of viscous flow for the blend is higher than that for the individual constituents. The blend membrane is found to give ca. 20% greater salt rejection and 70% higher flux than the single component membrane.