Concentration‐Dependent ROS Generation and Apoptosis Induction by a Thermoresponsive Tri‐Arm Block Copolymer

ABSTRACT

A thermoresponsive tri‐arm block copolymer, poly[(N‐isopropylacrylamide) ₃ ‐ b ‐(methyl methacrylate) ₃ ], was synthesized through reversible addition‐fragmentation chain transfer (RAFT) polymerization employing a tri‐arm trithiocarbonate chain transfer agent derived from 1,3,5‐tris(bromomethyl)benzene. Initially, the tri‐arm (PNIPAAm) ₃ macro‐RAFT agent was prepared and subsequently chain‐extended with hydrophobic PMMA segments to yield the tri‐arm diblock copolymer. Structural characterization using FT‐IR, ¹ H NMR, and GPC verified the successful formation of the copolymer and confirmed the controlled progression of polymerization. The resulting copolymer exhibited a tunable lower critical solution temperature (LCST) within the physiological range, which decreased with increasing PMMA incorporation and varied with polymer concentration (LCST 26°C–35°C). This modulation of thermal response indicated the influence of hydrophobic block content on phase transition behavior. Biologically, (PNIPAAm) ₃ ‐ b ‐(PMMA) ₃ demonstrated dose‐dependent in vitro cytotoxicity against Dalton's lymphoma cells associated with intracellular ROS elevation and induced morphological changes consistent with apoptosis, providing preliminary insights into its biological activity. Potential application as a thermoresponsive polymeric system.