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.

Tissue engineering and regenerative medicine are emerging as future approaches for the treatment of acute and chronic diseases. However, many challenging clinical conditions exist today and include congenital disorders, trauma, infection, inflammation and cancer, in which hard and soft tissue damage, organ failure and loss are still not treated effectively. Regenerative medicine has contributed to a number of innovations through artificial implants and biomedical materials, with advances are continually being made. Researchers are constantly developing new biomaterials and tissue engineered technologies to stimulate tissue regeneration in order to repair and replace damaged or malfunctioning organs. However, the challenge continues to lie in devising effective biomedical materials that can be implanted as scaffolds. Various approaches are emerging, according to the organ, tissue, disease and disorder. Scaffolds are implanted cell-free, or incorporated with stems cells, committed cells, or bioactive molecules. Irrespective, engineered biomaterials are required to regenerate and ultimately reproduce the original physiological, biological, chemical and mechanical properties over time. This is enabled by providing a three-dimensional architecture for cells to adhere, migrate, proliferate within, and differentiate appropriately for the growth of new tissues to provide a relevant structure, and in so doing, restore function. Biodegradable materials have been used extensively as regenerative therapies since their advent in early 20th century. One notable example is the development of surgical fixation devices. The selection, design and physicochemical properties of these materials are important and must consider biocompatibility, biodegradability and minimal cytotoxicity in the host to enable cell-proliferation, cell-matrix interactions and intercellular signalling for stimulating tissue growth. In this review, we critique the most studied and recently developed biodegradable

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Heterocycling: Diphenyl vinyl sulfonium salt 1 acts first as an electrophile, then a base, and then again as an electrophile in this operationally simple, high yielding, one‐pot synthesis of pharmacologically important morpholines, thiomorpholines, and piperazines. Compound 1 is an excellent synthon for the 1,2‐ethane dication.

Reaction of bromoethylsulfonium salt with 1,2-/1,3-aminoalcohols gave six- and seven-membered rings in good-to-excellent yields. The reactions proceed through generation of a vinyl sulfonium salt followed by annulation to give 1,4-heterocyclic compounds such as morpholines and benzoxazepines in a simple procedure. The method accommodates a range of nitrogen substituents and the amino alcohol can be substituted by amino thiols and diamines to give thiomorpholines, piperazines and benzodiazepines.