Natural Biomaterials in Photodynamic Therapy: Platforms for Photosensitizer Solubilization, Formulation, and Delivery

Photodynamic therapy (PDT) is a minimally invasive form of cancer treatment. However, many conventional photosensitizers (PSs) exhibit poor water solubility and limited tumor selectivity, leading to off-target effects that restrict clinical utility. Recently, naturally synthesized or extracted materials have gained increasing attention because of their biocompatibility, stimuli responsiveness, low toxicity, cost-effectiveness, and low immunogenicity in biological environments. Among diverse biomedical uses, drug-delivery platform development has advanced rapidly and might enhance PS delivery efficiency. In this review, we summarize recent progress on natural biomaterials for PDT, focusing on their application to formulate PS and delivery in oncology. Specifically, in this review, we discuss the advantages of oligosaccharides, biopolymers/proteins, and extracellular vesicles as formulation platforms, outline design and functional-modification strategies for natural biomaterial-based systems, and highlight how these approaches can further improve therapeutic outcomes in cancer PDT.