# Microalgae as a Source of Photosensitizers: Analytical Strategies and Biomedical Use in Photodynamic Therapy

## TL;DR

This review explores how microalgae can be used to create natural photosensitizers for photodynamic therapy, highlighting their potential in various medical fields.

## Contribution

The paper introduces microalgae as a sustainable source of photosensitizers and reviews their biomedical applications and analytical strategies.

## Key findings

- Microalgae-derived pigments can efficiently generate singlet oxygen for photodynamic therapy.
- Algal pigments show organelle-specific phototoxicity and therapeutic selectivity.
- Chemical modifications of algal pigments improve their photodynamic activity and translational potential.

## Abstract

Photodynamic therapy (PDT) is an established light-based treatment modality that relies on the activation of photosensitizers to generate reactive oxygen species (ROS) and induce localized cytotoxicity. In recent years, microalgae have emerged as a promising and sustainable source of natural photosensitizers due to their ability to biosynthesize structurally diverse pigments with strong light-harvesting capacity. This review provides a comprehensive, application-oriented analysis of microalgae-derived photosensitizers, focusing on chlorophylls and their derivatives, carotenoids, and phycobiliproteins. Particular attention is given to analytical strategies for pigment extraction, purification, and characterization, as well as to photophysical properties, subcellular localization, and ROS-mediated mechanisms underlying photodynamic activity. Recent advances in the chemical modification of algal pigments, including chlorin-based derivatives and 5-aminolevulinic acid–related systems, are critically discussed in relation to structure–activity relationships and translational performance. The accumulated evidence demonstrates that microalgae-derived pigments and their synthetic analogues can achieve efficient singlet oxygen generation, organelle-specific phototoxicity, and favorable therapeutic selectivity. Taken together, these findings highlight microalgae as a renewable and versatile platform for developing next-generation photosensitizers with broad biomedical potential in oncology, dermatology, and antimicrobial photodynamic therapy.