Research advances in nano-photodynamic therapy for treatment of cutaneous melanoma

Cutaneous melanoma is a highly malignant skin cancer with low survival rate. Traditional treatment such as surgery is associated with certain recurrence rate. Photodynamic therapy produces cytotoxic reactive oxygen species by photoactivating photosensitizers to kill tumor cells, which is a promising treatment for cutaneous melanoma. However, limitations of conventional photosensitizer, including low permeability, unspecific targeting, and inadequate therapeutic effect, significantly restrict the clinical application of photodynamic therapy in treating cutaneous melanoma. It is crucial to improve the effectiveness and safety of photodynamic therapy through modification of the photosensitizer. This review focuses on the research advances in nanophotodynamic therapy for cutaneous melanoma, including the types of nanoparticles and nano-photosensitizers, the release mechanism of photosensitizer, and the benefits and limitations of nanophotodynamic therapy. Nanoparticles can enhance the targeting capacity of photosensitizer, increase the intratumoral accumulation of photosensitizer, and improve the hypoxic microenvironment. In addition, multifunctional nanoparticles can synergize photodynamic therapy with fluorescence imaging, immunotherapy/gene therapy, chemotherapy, and photothermal therapy to achieve better treatment effectiveness and safety. Although nanophotodynamic therapy has high manufacturing cost, low reproducibility, and unconfirmed long-term in-vivo safety, it overcomes the limitations of traditional photodynamic therapy and offers a novel method for treatment of cutaneous melanoma.