Innovative applications of methylene blue: beyond the classic uses
While its historical uses (dyeing, antidote, fishkeeping) are well established, it is the exploration of new therapeutic frontiers that today generates scientific excitement. This chapter details the emerging applications, still at the research stage or in early clinical trials, that could redefine the future usefulness of methylene blue.
Cognitive neuroprotection and neurodegenerative diseases
The context: failure of amyloid therapies
Research into Alzheimer's disease, long focused on clearing amyloid plaques, has met with repeated failures. Methylene blue offers an alternative approach targeting the Tau protein and neuronal mitochondrial health.
Proposed neuroprotective mechanism
- Inhibition of Tau aggregation: the dye is thought to prevent abnormal Tau proteins from clumping together into neurotoxic tangles.
- Mitochondrial restoration: by acting as an alternative electron acceptor, it would support the energy metabolism of struggling neurons.
- Reduction of oxidative stress: a direct antioxidant action protecting neuronal membranes.
State of innovation
A purified derivative of methylene blue (LMTM - Leuco-Methylthioninium) is currently in phase 3 clinical trials. Preliminary results suggest a potential slowing of cognitive decline, especially in patients not taking other Alzheimer's medications.
Outlook: if confirmed, this would represent the first disease-modifying therapy that genuinely alters the course of the disease, based on Tau metabolism.
Antimicrobial photodynamic therapy (aPDT)
The antibiotic resistance crisis
Faced with the emergence of bacteria that are multiresistant to antibiotics, photodynamic therapy (aPDT) offers a physical rather than a chemical solution.
Principle of methylene blue aPDT
- Local application of a methylene blue solution to the infected area (wound, root canal, gum).
- Illumination with a specific red light (660 nm).
- Local production of singlet oxygen (ROS) that physically destroys bacterial membranes.
Major advantages
- No possible resistance: bacteria cannot develop genetic resistance to a massive physical oxidative attack.
- Broad spectrum: effective against Gram-positive and Gram-negative bacteria, fungi and viruses.
- Selectivity: the dye accumulates preferentially in bacteria compared with host human cells.
Emerging clinical applications
- Dentistry: disinfection of root canals and treatment of periodontitis.
- Dermatology: treatment of infected chronic ulcers and resistant acne.
- Surface disinfection: potential hospital application (self-disinfecting surfaces under light).
Memory enhancement and nootropic use
The "biohacking" use
Outside the strict medical setting, a community of "biohackers" is taking an interest in low-dose methylene blue as a nootropic (cognitive enhancer).
Scientific basis
Animal studies (rodents) show an improvement in short-term memory and learning retention under a low dose of methylene blue. The presumed mechanism is increased cerebral oxygen consumption and ATP production.
Clinical reality
No robust study in healthy humans validates this use. The risks (serotonergic drug interaction, impurities in non-pharmaceutical products) are real. This is an innovative but unvalidated and potentially risky application.
Treatment of vasoplegic shock
Critical care context
During certain cardiac surgeries or severe septic shock, the blood vessels dilate uncontrollably (vasoplegia), resisting conventional vasoconstrictor drugs (noradrenaline).
Mechanism of action
Methylene blue inhibits the enzyme soluble guanylate cyclase (sGC) and nitric oxide synthase (NOS). These enzymes are responsible for the excessive vascular relaxation. By blocking them, the dye restores vascular tone and raises blood pressure.
Clinical status
Increasingly frequent use in specialised cardiac intensive care as a rescue therapy. Regarded as a valid option when standard treatments fail.
Dermatological and anti-ageing applications
Collagen stimulation
Recent research (2017-2023) suggests that methylene blue stimulates the proliferation of skin fibroblasts and the synthesis of collagen and elastin.
Proposed mechanism
- Reduction of cutaneous oxidative stress (ROS)
- Mitochondrial stimulation of skin cells
- Protection against UV damage (paradoxical photoprotective effect at low dose)
Emerging products
A few niche cosmetics now incorporate methylene blue (often in a stabilised colourless or micro-dosed form), promising anti-ageing effects superior to retinol with less irritation. This is a field of intense commercial activity, although long-term clinical evidence is still lacking.
Intraoperative tumour marking
The surgical challenge
Visually distinguishing cancerous tissue from healthy tissue during an operation is difficult.
Innovation
Systemic or local injection of methylene blue before surgery. The dye accumulates preferentially in certain tumour tissues (parathyroid, sentinel lymph nodes in breast cancer). The surgeon can then visualise and excise the tumour more precisely.
Advantage: a negligible cost compared with specific radioactive or fluorescent tracers. A technique already used by some endocrine surgeons.
Summary table of innovations
| Application | Stage of development | Potential impact | Level of evidence |
|---|---|---|---|
| Alzheimer's neuroprotection | Phase 3 clinical trials | Major (revolutionary) | Mixed / Pending |
| aPDT therapy (dentist/wound) | Advanced clinical | High (antibiotic resistance) | Strong (local) |
| Nootropic (memory) | "Off-label" use / pre-clinical | Moderate | Weak (healthy humans) |
| Vasoplegic shock | Specialised hospital practice | Vital (rescue) | Strong (specific indications) |
| Anti-ageing cosmetics | Emerging commercial | Economic | Moderate (strong in vitro) |
| Guided surgery | Niche clinical practice | Practical | Strong (visual) |
Conclusion: an old molecule, multiple futures
Methylene blue is experiencing a second youth. Far from being a mere outdated dye, it is reinventing itself as a mitochondrial metabolic agent, an antimicrobial photosensitiser and a vascular modulator.
However, "innovative" does not mean "miraculous". Each new application must break through the wall of rigorous clinical trials in order to turn biological promise into therapeutic reality.
To learn how to prepare solutions suited to these potential uses (outside the strict medical setting), refer to the guide on preparing solutions.