Investigating the photosensitization activities of flavins irradiated by blue LEDs

Tuning the Flavin Core via Donor Appendage for Selective Subcellular Bioimaging and PDT Application

Herein, we report a novel flavin analogue as singular chemical component for lysosome bioimaging, and inherited photosensitizer capability of the flavin core was demonstrated as a promising candidate for photodynamic therapy (PDT) application. Fine-tuning the flavin core with the incorporation of methoxy naphthyl appendage provides an appropriate chemical design, thereby offering photostability, selectivity, and lysosomal colocalization, along with the aggregation-induced emissive nature, making it suitable for lysosomal bioimaging applications. Additionally, photosensitization capability of the flavin core with photostable nature of the synthesized analogue has shown remarkable capacity for generating reactive oxygen species (ROS) within cells, making it a promising candidate for photodynamic therapy (PDT) application.

Quantification of cellular phototoxicity of organelle stains by the dynamics of microtubule polymerization

Being able to quantify the phototoxicity of dyes and drugs in live cells allows biologists to better understand cell responses to exogenous stimuli during imaging. This capability further helps to design fluorescent labels with lower phototoxicity and drugs with better efficacy. Conventional ways to evaluate cellular phototoxicity rely on late-stage measurements of individual or different populations of cells. Here, we developed a quantitative method using intracellular microtubule polymerization as a rapid and sensitive marker to quantify early-stage phototoxicity. Implementing this method, we assessed the photosensitization induced by organelle dyes illuminated with different excitation wavelengths. Notably, fluorescent markers targeting mitochondria, nuclei, and endoplasmic reticulum exhibited diverse levels of phototoxicity. Furthermore, leveraging a real-time precision opto-control technology allowed us to evaluate the synergistic effect of light and dyes on specific organelles. Studies in hypoxia revealed enhanced phototoxicity of Mito-Tracker Red CMXRos that is not correlated with the generation of reactive oxygen species but a different deleterious pathway in low oxygen conditions.

Teaser

Microtubule dynamics in live cells allow quantification of cellular phototoxicity of fluorescent dyes in various conditions.

Riboflavin and Its Derivates as Potential Photosensitizers in the Photodynamic Treatment of Skin Cancers

Riboflavin, a water-soluble vitamin B2, possesses unique biological and physicochemical properties. Its photosensitizing properties make it suitable for various biological applications, such as pathogen inactivation and photodynamic therapy. However, the effectiveness of riboflavin as a photosensitizer is hindered by its degradation upon exposure to light. The review aims to highlight the significance of riboflavin and its derivatives as potential photosensitizers for use in photodynamic therapy. Additionally, a concise overview of photodynamic therapy and utilization of blue light in dermatology is provided, as well as the photochemistry and photobiophysics of riboflavin and its derivatives. Particular emphasis is given to the latest findings on the use of acetylated 3-methyltetraacetyl-riboflavin derivative (3MeTARF) in photodynamic therapy.

Enhancing the photosensitizing activity of natural flavins: Tuning the heavy-atom effect in the isoalloxazine series

Structure-photosensitizing activity relationships for a series of flavin analogues were investigated with the final goal of identifying the most potent photosensitizer in these series. The main structural modifications involved the introduction of various halogen atoms in C₇- and/or C₈-positions on the isoalloxazine ring. These compounds were synthesized by reacting judiciously-functionalized anilines with alloxan. The SAR trends showed that the photosensitizing activity increased with the size of the halogen atoms, confirming the importance of the heavy-atom effect on the photosensitizer's activity. The halogens in C₈ were more active than the di-substituted halogens, which in turn were more active than the C₇-substituted equivalents. However, even if the photosensitizing activity is slightly less important for the 7- compared to the 8-substituted derivatives, the 7-haloisoalloxazines are promising photosensitizers, as they present a better cellular toxicity profile than the 8-substituted analoges. The photosensitizing activity perfectly correlated with the determined fluorescence for the same compounds. Except for the dihalogeno derivatives, all the compounds were not toxic up to a 50 μM range.