Photodynamic Therapy Strategies and Mechanisms

Photodynamic therapy (PDT) harnesses light-activated chemical processes to induce selective cytotoxicity in diseased tissues. Central to PDT is the administration of a photosensitiser that, upon illumination within a defined wavelength window, undergoes electronic excitation. The excited sensitiser can transfer energy or electrons to molecular oxygen, generating reactive oxygen species (ROS) such as singlet oxygen and free radicals. These species oxidise cellular components, triggering apoptotic, necrotic or autophagic pathways, and can also disrupt tumour vasculature to starve malignant tissue of nutrients. Strategies in PDT encompass the rational design of sensitiser molecules—modifying core chromophores, central metals and peripheral substituents to tune photophysical properties and biodistribution—as well as advanced delivery systems, including polymeric micelles, liposomes and inorganic carriers. Precise control of drug-to-light interval (DLI), light dose and tissue oxygenation underpins treatment efficacy, and emerging protocols exploit vascular-directed illumination to collapse tumour blood flow. Beyond direct cytotoxicity, PDT elicits local inflammatory responses that may act as adjuvants to antitumour immunity. Contemporary research explores near-infrared (NIR) sensitisation for deeper tissue penetration, combination regimens with immunomodulators, and antimicrobial applications to address drug-resistant pathogens. Continuous refinement of photosensitiser chemistry and light-delivery technology is broadening the clinical and translational scope of PDT across oncology, infectious disease and beyond.

Research from Nature Portfolio

Recent studies have delineated how vascular-targeted illumination protocols can induce durable tumour regression. In a murine lung carcinoma model, a bacteriochlorin sensitiser was administered with varied drug-to-light intervals (15 min, 3 h, 72 h) and its effects on tumour oxygenation and blood flow were imaged in real time. Short-interval treatment focusing on vascular destruction led to rapid vessel occlusion, profound tissue hypoxia and complete tumour remission in a majority of treated animals. In vitro assays confirmed efficient sensitiser uptake, negligible dark toxicity and robust generation of singlet oxygen, superoxide and hydroxyl radicals. This work underscores the critical interplay between photosensitiser distribution, light timing and tumour microenvironment dynamics in maximising antineoplastic outcomes.

Photodynamic Therapy Strategies and Mechanisms publication trend

The graph below shows the total number of articles in photodynamic therapy strategies and mechanisms across all publications each year (not limited to Nature Index journals).

Technical terms

Photosensitiser: A molecule that absorbs light and transfers energy or electrons to generate reactive oxygen species.

Reactive oxygen species (ROS): Highly reactive molecules, including singlet oxygen, superoxide and hydroxyl radicals, responsible for oxidative damage to cells.

Singlet oxygen: An electronically excited form of molecular oxygen with enhanced reactivity toward biological substrates.

Vascular-targeted photodynamic therapy (V-PDT): A PDT modality aimed at disrupting tumour vasculature to induce hypoxia and secondary tumour cell death.

Drug-to-light interval (DLI): The time between photosensitiser administration and light exposure, which influences tissue distribution and treatment outcome.

References

1. Synthesis, Photo-Characterizations, and Pre-Clinical Studies on Advanced Cellular and Animal Models of Zinc(II) and Platinum(II) Sulfonyl-Substituted Phthalocyanines for Enhanced Vascular-Targeted Photodynamic Therapy. ACS Applied Materials & Interfaces (2024).
2. Bacteriochlorins and their metal complexes as NIR-absorbing photosensitizers: properties, mechanisms, and applications. Coordination Chemistry Reviews (2020).
3. Effects of Photodynamic Therapy with Redaporfin on Tumor Oxygenation and Blood Flow in a Lung Cancer Mouse Model. Scientific Reports (2019).