Improving the safety efficacy ratio of existing drugs is a current challenge to be addressed rather than the development of novel drugs which involve much expense and time. The efficacy of drugs is affected by a number of factors such as their low aqueous solubility, unequal absorption along the gastrointestinal (GI) tract, risk of degradation in the acidic milieu of the stomach, low permeation of the drugs in the upper GI tract, systematic side effects, etc. This review aims to enlighten readers on the role of pH sensitive hydrogels in drug delivery, their mechanism of action, swelling, and drug release as a function of pH change along the GI tract. The basis for the selection of materials, their structural features, physical and chemical properties, the presence of ionic pendant groups, and the influence of their pK_a and pK_b values on the ionization, consequent swelling, and targeted drug release are also highlighted.

The authors wish to make a change to their published paper [1].

Guar gum succinate (GGS) was chemically modified by reacting guar gum with succinic anhydride in the presence of 4-dimethylaminopyridine. Succination was confirmed by Fourier transform infrared (FTIR) spectroscopy with carbonyl bands at 1724 cm⁻¹ and ester linkage at 1567 cm⁻¹ of the succinate group. The resulting amorphous, GGS was used as a polymer host to prepare cost-effective solid polymer electrolyte (SPE) films via incorporating a blend of ethylene carbonate (EC), carboxymethyl cellulose (CMC), lithium triflate (LiTf) and lithium iodide (LiI). SPE system for GGS:EC (1.0:0.6) with 30 wt% LiTf showed highest conductivity of 6.29 × 10⁻⁵ S cm⁻¹ and GGS:CMC:EC (0.5:0.5:0.6) with 25 wt% LiI showed highest conductivity of 2.10 × 10⁻⁴ S cm⁻¹. FTIR revealed multiple complexation sites for ion mobility indicating that GGS possesses high prospects as a conductive SPE.