Fabrication of TiO ₂ Nanoparticles with High Colloidal Stability through Surface Modification via Biocompatible Block Copolymers and Heating

Titanium dioxide nanoparticles (TiO₂ NPs) possess unique physicochemical properties that make them attractive for various applications. However, poor colloidal stability under physiological conditions limits biomedical applications. To address this issue, we synthesized poly(oligoethylene glycol methacrylate) (POEGMA) and POEGMA-<i>block</i>-poly(2-methacryloyl oxyethyl phosphoryl choline) (POEGMA-<i>block</i>-PMPC) polymers bearing phosphonic acid end groups for anchoring to the TiO₂ surfaces. Dynamic light scattering revealed that the colloidal stability of TiO₂ NPs in phosphate-buffered saline improved with increasing molecular weights of the modified polymers. Furthermore, heat treatment after POEGMA-<i>block</i>-PMPC modification further improved the colloidal stability, most likely because of changes in the coordination structure between phosphonic acid and TiO₂. Importantly, the block copolymer-modified TiO₂ NPs retained their function as sonosensitizers after heating, enabling their potential in biomedical applications such as sonodynamic therapy.