Soft versus hard nanoparticles in the delivery of aromatic macrocycles for photodynamic therapy of cancer

Background: Photodynamic therapy is a medical strategy to treat some types of cancer. It is based on the use of a photosensitiser, usually porphyrin or phthalocyanine derivatives, to generate toxic species in the cells upon light irradiation. Aim: An overview of the different types of nanoparticles already investigated to deliver the photosensitisers until its target is given in this review. Materials and Methods: Previous literature and various scientific search engines were used for the review. Results: A classification of the nanoparticles based on the nature of their components, ‘hard’-inorganic and ‘soft’-organic, is made and several advantages and disadvantages about their uses are pointed out. Also, a comparative summary is outlined. Conclusion: There are still some drawbacks that need to be sorted out for photodynamic therapy to become a generalised cancer treatment. These could be overcome by using nanoparticles as carriers for the photosensitisers.