Spotlight on the delivery of photosensitizers: different approaches for photodynamic-based therapies.

Nanomedicine development allowed the discovery of new photosensitizers (PS) and drug delivery systems (DDS) to overcome current issues on phototherapy. Nano-engineered materials have the potential to improve the solubility of PS, control drug pharmacokinetics, decreasing side effects, increasing bioavailability, and overcoming multidrug resistance. A recent approach is the co-delivery of PS with other therapeutic agents in a multimodal platform for synergic and improved results. Areas covered: This paper discusses the delivery of PS-nanostructured platforms for conventional, photothermal, and antimicrobial photodynamic therapies, as well as in a recent therapeutic modality for photobiomodulation, covering applications of cancer diagnosis, targeting to skin pathogens, photoregeneration and wound healing. The focus of the present review is to describe the use of different DDS to enhance the therapeutic outcomes triggered by the combination of delivered PS, light, and oxygen. Expert opinion: Nanotechnology allowed the development of site-specific delivery of PS molecules, expanding possibilities poorly explored before to enhance photodynamic efficacy and extrapolate the concept to other treatment protocols. Research in this area embraces potential and pitfalls of PS delivery, allowing new clinical phase outcomes and long-term issues to be established, which will impact on several biomedical applications.