Marine polysaccharide-based photodynamic drug delivery systems (MP-PDDS) for anticancer and antibacterial therapies: Recent advances and future directions.

The vast marine ecosystem provides countless bioactive compounds, resulting in immense biodiversity characterized by biocompatibility, biodegradability, structural diversity, and chemical modifiability. Marine polysaccharides, including chitosan, alginate, carrageenan, fucoidan, chondroitin sulfate, and microbial polysaccharides, exhibit distinct charge properties, rheological behavior, receptor recognition, and chemical modifiability that optimize drug delivery platforms. In photodynamic therapy (PDT), light-activated photosensitizers (PS) generate reactive oxygen species (ROS) via Type I and/or Type II pathways, thereby enabling spatiotemporally controlled oxidative damage for therapeutic purposes. This review summarizes recent advances in marine polysaccharide-based photodynamic drug delivery systems (MP-PDDS) for anticancer and antibacterial applications. Representative marine polysaccharides, photosensitizer mechanisms, and Type I/Type II photochemical pathways are first introduced, followed by the construction and therapeutic effects of MP-PDDS hydrogels, nanoparticles, and other composite carriers. Across these systems, marine polysaccharides have been reported to achieve high encapsulation efficiency (96%), improve targeted release of PS (lasting for 72 h), and significantly reduce tumor volume (over 70%) and bacterial survival (over 90%). By discussing current limitations that hinder their clinical application and future perspectives, this review may provide useful guidance for designing more efficient and clinically translatable MP-PDDS.