Improved Simulated-Daylight Photodynamic Therapy and Possible Mechanism of Ag-Modified TiO2 on Melanoma

Simulated-daylight photodynamic therapy (SD-PDT) may be an efficacious strategy for treating melanoma because it can overcome the severe stinging pain, erythema, and edema experienced during conventional PDT. However, the poor daylight response of existing common photosensitizers leads to unsatisfactory anti-tumor therapeutic effects and limits the development of daylight PDT. Hence, in this study, we utilized Ag nanoparticles to adjust the daylight response of TiO2, acquire efficient photochemical activity, and then enhance the anti-tumor therapeutic effect of SD-PDT on melanoma. The synthesized Ag-doped TiO2showed an optimal enhanced effect compared to Ag-core TiO2. Doping Ag into TiO2produced a new shallow acceptor impurity level in the energy band structure, which expanded optical absorption in the range of 400–800 nm, and finally improved the photodamage effect of TiO2under SD irradiation. Plasmonic near-field distributions were enhanced due to the high refractive index of TiO2at the Ag-TiO2interface, and then the amount of light captured by TiO2was increased to induce the enhanced SD-PDT effect of Ag-core TiO2. Hence, Ag could effectively improve the photochemical activity and SD-PDT effect of TiO2through the change in the energy band structure. Generally, Ag-doped TiO2is a promising photosensitizer agent for treating melanoma via SD-PDT.Keywords:melanoma;simulated-daylight photodynamic therapy;Ag-doped TiO2;Ag-core TiO2