Molecular Reaction Mechanisms of Combination Treatments of Low-Dose Cisplatin with Radiotherapy and Photodynamic Therapy

Combination of low-dose cisplatin with radiotherapy or photodynamic therapy (PDT) is a novel cancer treatment. Using time-resolved femtosecond laser spectroscopy, we reveal the molecular mechanisms of the combinations of cisplatin with radiotherapy and PDT using indocyanine green (ICG) excited at 800 nm. DNA damage measurements confirm that electron-transfer reactions of cisplatin with electrons generated in ionizing radiation and with the ICG singlet excited state in PDT are responsible for the cytotoxic enhancements.