Fabrication of thermosensitive, star-shaped poly(L-lactide)-block-poly(N-isopropylacrylamide) copolymers with porphyrin core for photodynamic therapy

Thermosensitive, star-shaped porphyrin-cored poly(L-lactide)-block-poly(N-isopropylacrylamide) (SPPLA-PNIPAM) was synthesized via ring-opening polymerization (ROP) and reversible addition-fragmentation chain transfer polymerization (RAFT). The composition and properties of copolymer were discussed based on the results of NMR, IR and GPC. With PNIPAM block length decreasing, the morphology of SPPLA-PNIPAM copolymer in aqueous solution transformed hierarchically from spherical micelles through wormlike micelles to vesicles, and the lower critical solution temperatures (LCST) of the copolymer solutions were determined to be 37.9°, 37.2°, 35.9°, respectively. The in vitro study indicated that SPPLA-PNIPAM showed no significant dark cytotoxicity at concentrations up to 128 μg/mL, while showed apparent phototoxicity toward BEL-7402 cancer cells. Considering a high singlet oxygen quantum yield and suitable nominal physiologic LCST, it is expected that the SPPLA-PNIPAM copolymer is a promising stimulus-responsive candidate which has a potential application in photodynamic therapy (PDT).