Hydrogels based on graft copolymerization of 2-hydroxypropyl methacrylate/acrylate mixtures on amylose: swelling behaviour

Loading of Cefixime to pH sensitive chitosan based hydrogel and investigation of controlled release kinetics

Chitosan (biopolymer) and polyvinyl pyrolidone (PVP) with aminopropyletriethoxy silane (cross linker) based hydrogels were prepared and tested for controlled drug release. The drug release and kinetics were studied as a function of pH. Formulations were characterized by Fourier Transform Infrared (FTIR) and Thermogravimetric (TGA) analysis and TAP 32 hydrogel formulation was the most stable and hydrogel samples showed promising antibacterial activity against E. coli strain. The maximum swelling (4386%) was observed for TAP 32 formulation in distilled water, which was decreased with the concentration of ions. The diffusion exponent (n) values of all hydrogel formulations were recorded to be <0.5, which is an indication of Quasi-Fickian diffusion. The maximum swelling was observed at pH 2 and decreased at higher pH. The pH sensitivity of hydrogels found to be promising for their use in drug delivery, which was tested for cefixime drug. Drug release of 81.6% was observed for the period of 12 h in a simulated gastric fluid (SGF). The values of R² for zero order, first order, Higuchi, Hixson, Korsmeyer-Peppas and Baker-Lonsdale were 0.97, 0.9818, 0.99, 0.99, 0.88 and 0.80, respectively. The hydrogels based on chitosan and PVP revealed potential for controlled cefixime drug release in gastric pH medium.

Water Behavior of Poly(acrylic acid)/ Poly (acrylonitrile) Semi-Interpenetrating Polymer Network Hydrogels

Semi-interpenetrating polymer network (semi-LPN) hydrogels, composed of poly(acrylic acid) (PAAc) and poly(acrylonitrile) (PAN), were prepared using UV irradiation. The characteristics of semi-IPN hydrogels were investigated by swelling experiments, and differential scanning calorimetry (DSC). The semi-IPN hydrogels exhibited swelling ratio in the range of 24.1-81.8% at 35°C. The swelling ratio of the semi-IPN hydrogels depended on pH and temperature. DSC was used for the quantitative determination of the amounts of free and bound water. The free water contents in the semi-IPN hydrogel AN21, AN31, and AN41 were 1.2, 2.4, and 11.3% in pure water, respectively. Activation energies of semi-IPN hydrogels also were calculated.

Perspectives on: Strategies to Fabricate Starch-based Hydrogels with Potential Biomedical Applications

In this review, some strategies to fabricate starch-based hydrogels are summarized and presented. Hydrophilic hydrogels based on native starch, pure starch components and their derivatives are important due to their swellability in water, biocompatibility and biodegradability. For the preparation of chemically cross-linked starch-based hydrogels, one-step and two-step synthesis by free radical polymerization, cross-linking by chemical reaction of complementary groups and radiation-induced polymerization with the help of gamma or electron beams, are used. For the preparation of physically cross-linked starch-based hydrogels, a novel self-assembly method was used. Some advantages and disadvantages of these synthesis approaches are briefly discussed.