Tetrapyrrole photosensitisers, determinants of subcellular localisation and mechanisms of photodynamic processes in therapeutic approaches

Background: Tetrapyrrole photosensitisers are the main drugs used in the various photodynamic therapies. They are based on light-induced reactive oxygen species whose lifetimes are very short, limiting their diffusion in space. The photoinduced alterations primarily affect the labelled structures, at the systemic and subcellular levels. Thus, in parallel to the improvement of the photophysical and photochemical properties of photosensitisers, focus has been given to the parameters governing their localisation. Objectives and Methods: We analyse the parameters that support the efficiency of photosensitisers, paying particular attention to their structural and physicochemical characteristics, especially the dynamics of photosenitisers towards membranes. Conclusion: The determinants of systemic and subcellular targeting are discussed with regard to the induced response.