Phenylthiourea-Conjugated BODIPY as an Efficient Photosensitizer for Tyrosinase-Positive Melanoma-Targeted Photodynamic Therapy

Melanoma is the most threatening form of metastatic skin cancer that develops from melanocytes and causes a large majority of deaths due to poor therapeutic prognosis. It has significant limitations in treatment because it shows great resistance to chemotherapy, radiotherapy, and other therapeutic methods. A noninvasive and clinically accepted therapeutic modality, photodynamic therapy (PDT), is a promising treatment option, but it is limitedly applied for melanoma skin cancer treatment. This is because most of the photosensitizers are unlikely to be expected to have a remarkable effect on melanoma due to drug efflux by melanin pigmentation and intrinsic antioxidant defense mechanisms. Moreover, melanin is a dominant absorber in the spectral region of 500-600 nm that can cause the decreased photoreaction efficiency of photosensitizers. Herein, to overcome these drawbacks, we have developed a phenylthiourea-conjugated BODIPY photosensitizer (PTUBDP) for tyrosinase-positive melanoma-targeted PDT. In light of our results, it exhibited an enhanced cytotoxic efficacy compared to BDP, a parallel PDT agent that absence of phenylthiourea unit. PTUBDP shows outstanding effects of increased oxidative stress by an enhanced cellular uptake of the tyrosinase positive melanoma cell line (B16F10). This work presents increased therapeutic efficacy through the combined therapeutic approach, enabling enhanced reactive oxygen species (ROS) generation as well as overcoming the critical limitations of melanoma.