Dual-function microneedle array for efficient photodynamic therapy with transdermal co-delivered light and photosensitizers

Photodynamic therapy (PDT), as a globally accepted method for treating different forms of skin or mucosal disorders, requires efficient co-delivery of photosensitizers and corresponding therapeutic light. The adverse effects of intravenous injection of photosensitizers have been reduced by the development of microneedle arrays for transdermal local photosensitizer delivery. However, the drawbacks of the only available therapeutic light delivery method at the moment, which is directly applying light to the skin surface, are yet to be improved. This study presents a new strategy in which therapeutic light and photosensitizer were transdermally co-delivered into local tissues. A flexible dual-function microneedle array (DfMNA) which contains 400 microneedles was developed. Each microneedle consists of a dissolvable needle tip (140 μm in height) for delivering the photosensitizer and a transparent needle body (660 μm in height) for guiding therapeutic light. Using port-wine stains, which is a frequently occurring skin disorder caused by vascular malformation, as a model disease, the effectiveness of DfMNA mediated PDT has been verified on mice. Compared with the standard operation procedure of clinical PDT, the DfMNA decreases the amount of photosensitizer from 300 μg to 0.5 μg and reduces therapeutic light irradiance from 100 mW cm⁻² to 60 mW cm⁻² while realizing better treatment effects. As a result, the skin damage and the burden on the metabolic system have been alleviated. The DfMNA has a remarkably reduced photosensitizer amount and, for the first time, realized transdermal delivery of therapeutic light for PDT, thus avoiding the disadvantages of existing PDT methodologies.