pH-sensitive polymers for drug delivery

Various pH-sensitive polymers have been developed for biomedical applications and recently attracted much attention for pH targeting nanomedicine. Recent development of pH-sensitive polymer systems that sharply respond to specific pH environment in solid tumors and cells and demonstrate modulated properties (e.g., triggered drug release at extratumoral pH, ligands or cell penetrating peptides exposure by shielding/deshielding mechanism or by pop-up mechanism, and endosomal pH targeting) have led significant progress in tumor targeting technology. These pH-sensitive polymer systems combined with nanotechnology could be utilized as an alternative strategy to traditional targeting systems to overcome major problems in current chemotherapy represented by non-specific tissue distribution of the drugs, tumor heterogeneity, and multidrug resistance (MDR) against anticancer drugs. This review highlights recent progress of pH-sensitive polymers with special emphasis on pH targeting nanomedicine.