A review of the photodynamic application of 5-aminolevulinic acid, hypericin and phthalocyanines in dermatology

Abstract: Ultraviolet radiation can damage human skin leading to photo-aging and cancer. Treatment options for skin cancers are available. Amongst them, there is photodynamic therapy (PDT), the treatment modality that involves a photochemical reaction between a light sensitive compound, visible light and tissue oxygen. In PDT, a photosensitive compound also called photosensitizer (PS) is administered and allowed to accumulate in the cancerous tissue then irradiated with light corresponding to absorption wavelength of the PS, in the presence of molecular oxygen, to produce cytotoxic species that kill the cancerous tissue. PDT is increasingly used and studied globally for the treatment of different classes of cancers because of its selective destruction of diseased tissue or cancer. Newly developed non-invasive imaging technologies including photodynamic diagnosis, may assist with early identification of skin cancer to reduce the rates of morbidity and mortality following treatment. Photodynamic diagnosis (PDD) is a diagnostic modality defined from the PDT principle. It utilizes light and fluorescent PS to highlight tumour cells from normal cells. Excitation of PS by appropriate light source causes them to fluoresce over well-defined spectral regions. Therefore, the fluorescent properties of PSs can serve as an important diagnostic tool to highlight cancer at an early stage of development. In this review, our knowledge about PDT and PDD of skin cancers using 5-aminolevulinic acid (ALA), Hypericin and phthalocyanines as photosensitizers is presented