The article highlights the recent approaches on the design and synthesis of drug delivery systems with a dynamic covalent bond

i.e.benzoic-imine

that renders the responsiveness of the vehicles to the pH changes under physiological conditions.Although the characteristics of Schiff base in chemical compounds and polymers have been well documented

recent reports demonstrate the advantages of the derivative benzoic-imine bond on the construction of pH sensitive polymeric micelles

nanoparticles and injectable hydrogels for pharmaceutical applications.In those systems

the benzoic-imine linkage is stable at physiological pH (7.4)

and hydrolyzes following a pH drop to mild acidic

which covers the extracellular pH of solid tumor (6.5)

endosome and lysosome environments (5~6.5).Therefore the benzoic-imine containing delivery systems are promising in tumor-targeting and intracellular delivery.