Benzoic-Imine-Based Physiological-pH-Responsive Materials for Biomedical Applications

The benzoic imine is a dynamic covalent bond, which is stable around neutral pH value (ca. 7.4), but starts to hydrolyze at the extracellular pH value of solid tumors (ca. 6.5) and rapidly disintegrates at endosome and lysosome pH values (ca. 4.5-6.5). This characteristic is promising for the construction of physiological-pH-responsive materials, such as polymeric micelles, nanoparticles, and hydrogels for pharmaceutical and tissue-engineering applications. This Focus Review summarizes recent progress in the design and synthesis of pH-sensitive materials that contain the benzoic imine bond with biomedical objectives.