pH-responsive drug delivery systems as intelligent carriers for targeted drug therapy: Brief history, properties, synthesis, mechanism and application

There are different pH-sensitive systems for biomedical applications that have recently been considered for pH targeting nanomedicine. In this review, we examine some of the most recent literature studies on pH-responsive drug delivery system (DDS) synthesis, properties, mechanisms, and applications. pH-sensitive DDSs are gaining popularity because they deliver the drug at the precise time required by the disease's pathophysiology, resulting in improved patient therapeutic effectiveness, protection, and compliance. Improvement of the safety, the efficacy of available medications is challenging, rather than the production of new medications, which need more cost and time. Such pH-sensitive polymer systems in combination with nanotechnology are applicable as an alternative method to traditional targeting systems for overcoming main challenges in present medication such as non-specific tissue distribution of the drugs, a variety of factors influencing drug effectiveness, including decreased aqueous solubility, uneven absorption in the gastrointestinal (GI) tract, degradation in the acidic stomach, decreased drug permeation in the upper GI tract, and systemic side effects. The current review presents an insight on the current status of pH-responsive DDSs obtained with organic polymers or inorganic materials, such as methods for overcoming GI barriers, growth problems, and prospects, considering technology trends for boosting drug bioavailability, drug release mechanisms from pH-responsive systems, and their used to deliver the drug.