A pharmaceutical study on photodynamic therapy of skin diseases

Abstract

Sunlight, either alone or in combination with certain plant extracts containing psoralens (photosensitizers) had been used in the ancient times for the treatment of various skin conditions such as psoriasis and vitiligo. Since then, several studies have focused on the therapeutic effects of light and its potential applications in skin diseases. Topical photochemotherapy or PDT has emerged as an effective and safe therapeutic option for the management of various skin cancers, lesions and infections. This modality involves topical delivery of a natural or synthetic photosensitizer followed by selective irradiation of the affected lesions with a suitable light resulting in cell death via necrosis or apoptosis. Topical PDT has advantages over the conventional therapies for skin diseases since it is highly effective, non-invasive, selective, relatively sparing normal tissues without cumulative toxic effects, and can be repeated several times for outpatients. However, most of the applied photosensitizers are highly hydrophobic with poor skin permeation, and hence require incorporation within nano-drug delivery systems. Among the nanosystems commonly employed for efficient topical delivery of photosensitizers are lipid nanoparticles and vesicular systems. Among the natural photosensitizers are psoralens such as bergamot oil, which are known to induce phototherapeutic activity when applied with UV light exposure.