Microalgae-based dosimetry for monitoring blue light exposure

Blue light therapy is increasingly used to treat various skin conditions like acne, psoriasis and neonatal hyperbilirubinemia. Yet, excessive blue light exposure can also negatively impact human health by disrupting circadian rhythms, generating free radicals and damaging skin barrier function. Quantifying personal blue light exposure is therefore essential for optimizing therapeutic efficacy while preventing side effects. However, current blue light dosimetry techniques require complex, expensive instrumentation, making routine monitoring impractical. In this feasibility study, we explored the potential for developing a blue-light dosimeter that uses the colour changes of photodegraded microalgae to measure blue light doses relevant for phototherapy. Two fibre-coupled light-emitting diodes (LEDs), one emitting at 415 nm and the other at 455 nm, were used. A strain of the green microalga Schizochlamys sp. (Chlorophyceae) exhibited a photobleaching response upon blue light irradiation, with colour changes quantitatively linked to exposure dose. This approach enables real-time monitoring and assessment of blue light exposure in a variety of contexts, including the workplace, the home and healthcare facilities, in a cost-effective and user-friendly way.