An injectable thermosensitive PLGA-PEG-PLGA hydrogel integrated with coordination-driven self-assembled MTX-Mn...

The treatment of malignant melanoma, an aggressive skin cancer with high recurrence and metastatic potential, often presents challenges due to systemic toxicity and multidrug resistance in current therapies. In this study, we develop a localized therapeutic platform by integrating methotrexate-manganese (MTX-Mn) coordination nanoparticles into a thermosensitive PLGA-PEG-PLGA (PPP) hydrogel to achieve sustained and site-specific drug delivery for melanoma treatment. MTX-Mn nanoparticles were synthesized through coordination-driven self-assembly and comprehensively characterized by FTIR, ¹H NMR, TEM, EDS, and zeta potential analyses, confirming successful coordination and uniform nanoscale features. In vitro experiments demonstrated that MTX-Mn significantly inhibited melanoma cell proliferation and migration. Flow cytometry further revealed that MTX-Mn induced pronounced G0/G1 cell-cycle arrest and effectively promoted apoptosis, which was confirmed by TUNEL staining. Mechanistic investigations indicated that MTX-Mn triggered severe mitochondrial dysfunction, including ultrastructural damage, elevated mitochondrial ROS generation, and collapse of mitochondrial membrane potential (JC-1), suggesting a mitochondria-associated antitumor mechanism. In vivo, peritumoral administration of PPP/MTX-Mn markedly suppressed tumor growth in a melanoma-bearing mouse model, reduced the tumor burden, and significantly decreased Ki-67 expression. Histological evaluation of major organs by H&E staining revealed no obvious pathological abnormalities, supporting good in vivo biosafety. Overall, this MTX-Mn-loaded thermosensitive hydrogel provides a promising strategy for effective and safe localized melanoma therapy.