Microalgae, being photosynthetic microorganisms, thrive in both marine and freshwater environments 1. Their ubiquitous presence spans various habitats, from lakes and oceans to wastewater facilities and even deserts 2. They have gained significant attention for their potential applications in various fields, including bioremediation, biofuel production, environmental agents for wastewater treatment, cosmetics and food production 3,4. Microalgae are cultivated as a source of highly valuable molecules, such as polyunsaturated fatty acid oils, pigments, and stable isotope biochemicals 5. Additionally, their rapid growth rates and manipulatable nature make them promising candidates for genetic engineering, paving the way for enhanced production of valuable metabolites and novel bioinsecticides 3.
The growth and composition of microalgae biomass are influenced by several environmental factors, such as light, media composition, and growth conditions including pH, temperature, and CO2 supply 6,7. Microalgae grow faster as light intensity increases, until they reach a saturation point, beyond which higher light intensities can lead to photoinhibition 8. Studies have shown that microalgae have the ability to absorb and respond to different light wavelengths 9. While most studies on light's impact on algae have centered on irradiance, several studies have demonstrated that algal metabolism and growth are also influenced by spectral composition 10. Blue light, which has a wavelength range of roughly 400–500 nm, strongly drives photosynthetic activity in microalgae 11,12.
The impact of blue light on skin health is influenced by the wavelength and the power of exposure. In controlled doses, high-energy blue light can serve as a therapeutic approach for skin disorders, effectively reducing dermatological issues 12. In fact, blue light phototherapy is known to treat several skin diseases including acne, psoriasis, atopic dermatitis, eczema 13. Phototherapy is also employed as a treatment modality for hyperbilirubinemia in neonates, commonly known as neonatal jaundice 14. However, excessive blue light exposure can disrupt circadian rhythms, induce free radical production, damage mitochondrial DNA, and delay skin barrier recovery 12,13. According to french agency for food, environmental and occupational health & safety (Agence nationale de sécurité sanitaire de l’alimentation, de l’environnement et du travail, ANSES), the effect of exposure to blue light on the occurrence of skin diseases is possible, although exposure levels, exposure durations, and long-term effects still need to be better defined. These effects therefore seem to depend on the dose received and the duration of exposure 15.
Given the potential health implications, it is essential to assess and regulate blue light exposure. Therefore, this study aims to explore the feasibility of microalgae as a blue light dosimeter, especially for acne and psoriaris vulgaris treatments.
When microalgal photosynthetic components like chlorophyll absorb blue photons, they transition to higher energy states, facilitating subsequent photochemical and electron transport processes 11. However, blue light irradiance rates, that are either too high or too low, can create stress and reduce growth. There is often an optimal balance to maximize growth rates and desired metabolic outputs from microalgae 1. Excessive light exposure can harm microalgal cells through a variety of mechanisms, including the generation of reactive oxygen species within thylakoid membranes 16.
Microalgae are readily available and can be grown in controlled laboratory settings, ensuring consistency and reproducibility. They are also relatively inexpensive to maintain, making them a cost-effective solution for blue light dosimetry. Additionally, microalgae are non-invasive; thus, they can be used to measure blue light exposure without harming the person being measured.