Photodynamic therapy (PDT) is an emerging cancer treatment based on the interactions between light, a photosensitizing drug and oxygen, which create reactive oxygen species (ROS), killing cells in a localized region. Although PDT is efficient for the local destruction of tumors, the treatment is still ineffective in systemic tumor elimination, so other treatment conditions combined with PDT are utilized for maximum effectiveness. PDT has become of interest as a potential partner of chemotherapy when recent research has shown that the two treatments combined show a synergistic effect against cancer. To take advantage of the potential combination between chemotherapy and PDT, there has been a focus on exploring compounds that are designed to improve both treatments simultaneously. Supramolecular coordination complexes (SCCs) have been of particular interest, combining the anticancer properties of organoplatinum(II) with the fluorescence properties of diverse photosensitizing agents via the spontaneous formation of metal-ligand bonds. The fluorescent properties of a photosensitizer are altered by a change in the ligand and therefore medical research has been exploring new fluorescent ligands to bind to the platinum core. Herein, the properties of two potential fluorescent ligands, boron dipyrromethene (BODIPY) and tetra(4-pyridyl)porphyrin (TPP) were investigated for their anticancer applications in combination with organoplatinum(II) due to the rare occurrence of highly fluorescent SCCs with BODIPY ligands and the need to further improve SCCs with commonly used porphyrin-based TPP ligands (1,2). The results showed that the combination of organoplatinum(II) and both BODIPY and TPP ligands were found to improve the combinational treatment of chemotherapy and photodynamic therapy; however, SCCs with TPP ligands were found to be more effective due to higher singlet oxygen (1O2) and quantum yields and reduced cytotoxicity in vivo (1,2). This shows that TPP ligands were effective for photochemotherapy and provides a general scaffold to further develop multifunctional agents for photodynamic therapy applications.
(1) Zhou, J.; Zhang, Y.; Yu, G.; Crawley, M. R.; Fulong, C. R. P.; Friedman, A. E.; Sengupta, S.; Sun, J.; Li, Q.; Huang, F.; Cook, T. R. Highly Emissive Self-Assembled BODIPY-Platinum Supramolecular Triangles. J. Am. Chem. Soc. 2018, 140, 7730−7736.
(2) Yu, G.; Yu, S.; Saha, M. L.; Zhou, J.; Cook, T. R.; Yung, B. C.; Chen, J.; Mao, Z.; Zhang, F.; Zhou, Z.; Liu, Y.; Shao, L.; Wang, S.; Gao, C.; Huang, F.; Stang, P. J.; Chen, X. 1. A discrete organoplatinum(II) metallacage as a multimodality theranostic platform for cancer photochemotherapy.
Nature Comm. DOI: 10.1038/s41467-018-06574-7.