Simulation on Transdermal Drug Delivery for Photodynamic Therapy

Photodynamic therapy (PDT) is an effective treatment for skin conditions. Transdermal delivery in PDT allows direct targeting of skin lesions with reduced systemic exposure, making it a safer option. However, challenges like poor drug absorption and limited penetration depth limit its use. Addressing these issues and optimizing treatment parameters are key to improving transdermal PDT. This study utilized COMSOL Multiphysics to simulate transdermal PDT, coupling oxygen and photosensitizer transport with light propagation to calculate ROS distribution and evaluate the efficacy. ROS concentration decreases with depth. Increasing 5-ALA ointment concentration from 10% to 20% improves superficial concentration but only increases effective depth by 4%. Reducing irradiance and extending exposure time improves photosensitizer distribution, expanding the treatment range by 21%. The range of transdermal PDT is primarily influenced by photosensitizer distribution, determined by exposure time. Optimizing exposure time enhances efficacy, supporting its application in superficial skin disease.