Syntheses and Identification of New Dithiophosphinic Acid Complexes and Their Potential as Photodynamic Agents in Cancer Therapy.

Background: The photo-efficacy of oncological phototherapy for both internal and external tumors is encouraging. When light and photochemotherapeutic drugs are applied together, precise cancer targeting, minimal invasiveness, and innovative modes of action are made possible. Current developments in photoactive compounds and new light sources are promising for further advancement.

Objective: When designing photosensitizers, metal complexes may be advantageous since the metal can enhance stability and photocytotoxicity while facilitating their localization and quantification. The absorption spectra of photosensitizers limit their excitation wavelengths, which impact light tissue penetration that differs in various organs. Since longer wavelength light penetrates deeper, PDT is typically carried out at wavelengths greater than 620 nm. Additionally, employing lower intensity (>4-8 J/cm²) energy can greatly lessen the pain and discomfort induced by red-light PDT.

Methods: Low-level laser therapy exposure was used to assess the dithiophosphinic acid complexes' photodynamic treatment efficacy in MCF-7 cells. Following the administration of the complexes at concentrations within IC₅₀ values, red light (4 J, 780 nm) was applied to the cells. Afterward, MCF-7 cells were cultured for 24 hours to evaluate the photodynamic effects of the compounds on cancer cells. Cell viability was assessed using the XTT assay kit.

Results: DTPA complexes have shown effectiveness as photodynamic agents in cancer therapy, with Ni(II) and Ni(II)-pyridine complexes demonstrating significant cytotoxicity against cancer cells.

Conclusion: Light-activated cancer cell therapies are promising, and the synthesized complexes affect the cell cycle and apoptosis-regulating proteins. The compounds can be employed as anticancer agents and a fine starting template for photodynamic drug design.