New avenues in the design and potential application of metal complexes for photodynamic therapy

Photodynamic therapy (PDT) requires a photosensitizing agent, which can undergo visible light activation, yielding reactive oxygen species and/or radical species. The key physical properties and desirable attributes of established PDT photosensitizer agents are discussed, together with a consideration of the role that photoactive metal coordination complexes may have in the future design of such agents. A number of classes of metal complex are included with a focus upon their ability to generate singlet oxygen, and prior indications of biological utility, compatibility and cytotoxicity through cellular imaging work and DNA binding behaviour.