Direct Polymerization Approach to Synthesize Acid-Degradable Block Copolymers Bearing Imine Pendants for Tunable pH-Sensitivity and Enhanced Release.

The development of effective approaches to synthesize smart amphiphilic block copolymers (ABPs) exhibiting acid-responsive degradation through the cleavage of acid-labile imine bonds is extensively explored for controlled release of encapsulated biomolecules, particularly in drug delivery. Here, a new approach based on direct polymerization utilizing a controlled radical polymerization technique to synthesize acid-degradable ABPs bearing pendant imine linkages in hydrophobic block is reported. The approach centers on the synthesis of a novel methacrylate bearing benzoic imine group that can be polymerized to form the hydrophobic imine pendant block. The formed ABPs respond to mild acidic pHs equivalent to tumoral and endosomal/lysosomal acidic environments. This causes the dissociation of self-assembled nanoassemblies through change in their hydrophilic/hydrophobic balance upon the cleavage of pendant imine linkages to the corresponding aldehyde and primary amine, thus leading to the enhanced release of encapsulated drugs. The proof-of-concept results suggest that this robust approach is versatile to further design advanced nanoassemblies responding to dual/multiple stimuli, thus being more effective to intracellular drug delivery.