Temperature and pH responsive smart nano carriers for drug delivery: Synthesis strategies, mechanism of action and biomedical applications-an updated review

Stimuli responsive nanocarriers provide enhanced versatility and functionality in biomedical applications because they are made to respond to various types of internal stimuli such as pH and redox potential and external stimuli such as magnetic fields, light, and heat. Recent advancements have led to the synthesis of multi-stimuli-responsive systems which uses the combination of multiple stimuli for more sophisticated control, increased stability, and enhanced therapeutic efficacy in highly complex biological environments. Smart nanocarriers can be engineered through controlled radical polymerization or via amphiphilic self-assembly so that they contain distinct blocks which exhibit dynamic transitions between hydrophobic and hydrophilic states or experience swelling through electrostatic repulsion in response to environmental stimuli. The physical changes associated with these types of nanocarriers provide for precisely regulated and triggered release of drugs, therefore making them important platforms for site-directed therapy for cancer, intracellular delivery of genetic material, and stimuli-controlled-release systems. The inherent ability of smart nanocarriers to target particular organs or cells also enhances the targeting accuracy of cytotoxic drug delivery systems resulting in minimizing side effects. This updated review presents an detailed information of the different types of stimuli-responsive nanocarrier systems, synthesis strategies, mechanisms of action and recent advances and challenges associated with drug delivery research.