Synthesis and characterization of thermosensitive, star-shaped poly(ε-caprolactone)-block-Poly(N-isopropylacrylamide) with porphyrin-core for photodynamic therapy

Thermosensitive, amphiphilic, star-shaped poly (ε-caprolactone)-block- poly (N-isopropylacrylamide) with prophyrin-core (SPPCL-b-PNIPAAm) was synthesized by ring-opening polymerization (ROP) and reversible addition-fragmentation chain transfer polymerization (RAFT) and characterized by NMR, IR, GPC in this study. The optical transmittance results showed that the lower critical solution temperatures (LCST) of the copolymer solutions were attractively close to normal physiologic temperature at around 37 °C. Due to its amphiphilic property, the obtained SPPCL-b-PNIPAAm had a low critical micelle concentration (CMC) in an aqueous solution and self-assembled into micelles in water. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis of micelle morphology revealed a well-defined spherical shape with a diameter of around 100 nm. Moreover, SPPCL-b-PNIPAAm micelles obtained high singlet oxygen quantum yields and indicated a sensitivity to temperature, suggesting that the SPPCL-b-PNIPAAm was a stimulus-responsive photosensitizer which had a potential application in targeted photodynamic therapy. [Figure not available: see fulltext.]