Recent Advances in pH-Sensitive Polymeric Nanoparticles for Smart Drug Delivery in Cancer Therapy

Rapid developments in the field of nanoparticles during the last decades have led to its increased application in drug delivery approaches. The advantages of nano-based drug delivery systems include improved therapeutic efficacy of drugs and the reduction of side effects. A plethora of different nanoparticles have been explored as drug carriers for the effective treatment of cancers. Of the various organic/inorganic nanoparticles, polymeric nanoparticles have fulfilled an integral role in the advancement of drug delivery systems by virtue of the ease to incorporate and modify targeting moieties in combination with controlled drug release over prolonged periods. Furthermore, polymeric nanoparticles facilitate theranostic treatment by the incorporation of imaging agents in addition to therapeutics. Recently, stimuli-responsive polymeric nanoparticles emerged as smart drug carriers, in which drug release is affected by physical and/or chemical structural changes induced by a specific stimulus (e.g. pH, temperature, and specific enzymes). The use of these nanocomposites reduces premature drug release and maintains effective drug levels at the pathological target. This review aims to highlight advances in stimuli-triggered drug delivery approaches using polymeric nanoparticles with a focus on pH-sensitive drug- and theranostic delivery systems.