Light-Emitting Photon-Upconversion Nanoparticles in the Generation of Transdermal Reactive-Oxygen Species

Common photosensitizers used in photodynamic therapy do not penetrate the skin effectively. In addition, the visible blue and red lights used to excite such photosensitizers have shallow penetration depths through tissue. To overcome these limitations, we have synthesized ultraviolet and visible light emitting, energy-transfer based upconversion nanoparticles, and co-encapsulated them inside PLGA-PEG nanoparticles with photosensitizer protoporphyrin IX. Nd3+ has been introduced as sensitizer in the upconversion nanostructures to allow their excitation at 808 nm. The subcytotoxic doses of the hybrid nanoparticles have been evaluated on different cell lines (i.e., fibroblasts, HaCaT, THP-1 monocytic cell line, U251MG, and mMSCs cells). Upon NIR light excitation the upconversion nanoparticles emitted UV and VIS light which consequently activated the generation of reactive oxygen species (ROS). In addition, after irradiating at 808 nm, the resulting hybrid nanoparticles containing both upconversion nanopartic...