Photodynamic Therapy Using Methylene Blue-Loaded Nanoparticles

Photodynamic therapy (PDT) employs a photosensitiser, light of an appropriate wavelength and molecular oxygen to generate cytotoxic reactive oxygen species (ROS), leading to targeted cell death. Methylene blue (MB) is a widely studied photosensitiser owing to its high singlet oxygen quantum yield, favourable absorption in the red spectrum and established safety profile. However, free MB suffers from rapid photobleaching, limited tissue penetration and off-target interactions. Loading MB into nanoparticle carriers addresses these limitations by enhancing photostability, enabling controlled release, improving biodistribution and providing opportunities for surface functionalisation to achieve active targeting. Various nanoplatforms—including polymeric nanoparticles, liposomes, mesoporous silica and noble metal constructs—have been engineered to optimise MB loading, preserve photophysical properties and increase cellular uptake. These advances have expanded the scope of MB-PDT from oncological indications such as cutaneous and breast malignancies to antimicrobial and dental biofilm applications, reinforcing its translational potential and global significance.

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Photodynamic Therapy Using Methylene Blue-Loaded Nanoparticles publication trend

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Technical terms

Photodynamic Therapy (PDT): A treatment modality combining light, a photosensitiser and oxygen to generate ROS that selectively destroy target cells.

Methylene Blue (MB): A cationic phenothiazinium dye used as a photosensitiser in PDT, notable for its singlet oxygen yield and red-light absorption.

Photosensitiser: A light-activated compound that transfers energy to molecular oxygen, producing ROS for therapeutic effects.

Reactive Oxygen Species (ROS): Highly reactive molecules, such as singlet oxygen, that induce oxidative damage leading to cell death.

Nanoparticles: Colloidal carriers, typically 1–200 nm in size, designed to improve payload stability, delivery and targeting.

Mesoporous Silica Nanoparticles (MSNs): Silica-based carriers with tunable pore structures for high-capacity loading and controlled release of therapeutic agents.

Sonophoresis: A technique using ultrasound to transiently increase skin permeability, enhancing transdermal drug delivery.

Photobleaching: The irreversible loss of a dye’s ability to absorb light, reducing photosensitiser efficacy over repeated illumination.

References

1. Nanoencapsulation of Methylene-Blue for Enhanced Skin Cancer Cell Phototoxicity and Cutaneous Penetration in Association with Sonophoresis. Pharmaceutics (2023).
2. One-pot synthesis and covalent conjugation of methylene blue in mesoporous silica nanoparticles – A platform for enhanced photodynamic therapy. Colloids and Surfaces B Biointerfaces (2024).
3. Methylene-Blue-Encapsulated Liposomes as Photodynamic Therapy Nano Agents for Breast Cancer Cells. Nanomaterials (2018).
4. Biogenic Gold Nanoparticles Decrease Methylene Blue Photobleaching and Enhance Antimicrobial Photodynamic Therapy. Molecules (2021).
5. Papain gel containing methylene blue for simultaneous caries removal and antimicrobial photoinactivation against Streptococcus mutans biofilms. Scientific Reports (2016).