UV Irradiation-Induced Cyclic-to-Linear Topological Changes of a Light/pH Dual-Sensitive Cyclic Copolymer for Enhanced Drug Delivery.

Cyclic polymers with cleavable backbones triggered by either external or internal stimuli can realize simultaneous extracellular stability and intracellular destabilization of cyclic polymer-based nanocarriers but remain seldom reported. To this end, we prepared herein cyclic-ONB-P(OEGMA- st -DMAEMA) ( c -ONB-P(OEGMA- st -DMAEMA)) with a light-cleavable junction in the polymer backbone based on oligo (ethylene glycol) monomethyl ether methacrylate (OEGMA) and N,N-dimethylaminoethyl methacrylate (DMAEMA) using a light-cleavable atom transfer radical polymerization (ATRP) initiator containing an o-nitrobenzyl (ONB) ester group. Together with the pH-sensitivity of DMAEMA, c -ONB-P(OEGMA- st -DMAEMA) shows a light-cleavable mainchain and pH-sensitive side chains. Notably, doxorubicin (DOX)-loaded c -ONB-P(OEGMA 4 -st-DMAEMA 38 ) (C2) micelles mediated an IC 50 value of 2.28 μg/mL in Bel-7402 cells, which is 1.7-fold lower than that acquired without UV irradiation. This study thus reported the synthesis of a cyclic copolymer with a UV-cleavable backbone and uncovered the effects of topological modulation on the in vitro controlled release properties of cyclic polymers.