Synthesis, Characterization of NR@SiO2/PNIPAm-co-Ppa Composite Nanogel and Study On Its Application in Photodynamic Therapy.

In the present study, a novel composite nanogel based on fluorescence resonance energy transfer (FRET) and its application for photodynamic therapy is reported. First of all, nanoparticles of silica doped with Nile Red (NR) were prepared by Stöber method, then they were decorated by γ-methacryloxypropyltrimethoxysilane (MPS) to prepare MPS decorated NR@SiO2 nanoparticles, and finally they were copolymerized with N-isopropylacrylamide (NIPAm) and Pyropheophorbide-a (Ppa) by free radical copolymerization, and composite nanogel of NR@SiO2/PNIPAm-co-Ppa was fabricated. The microstructure of the as-prepared nanogel was characterized by Fourier transform infrared spectrum (FTIR), photoluminescence (PL), UV-Visible spectrophotometer (UV-Vis), dynamic light scattering (DLS) and transmission electron microscopy (TEM). PL spectrum indicated that, under irradiation of visible light source, energy can be transferred from NR to Ppa. UV-Vis spectrum demonstrated that aggregation of Ppa is prevented efficiently and Ppa exists as "monomer" state in the composite nanogel. Under irradiation of laser, singlet oxygen (1O2) can be produced efficiently by excited nanogel. The in vitro cytotoxicity test showed that HeLa cells can be killed by the composite nanogel.