Breathing Laser-SpectralMapping of Cavity-EnhancedRedox Reactions with Subcellular Resolution

Precise and dynamic observation of redox reactions in living organisms holds significant importance for the study of physiological processes and pathological mechanisms. However, the current technologies still make it challenging to monitor this process in a nondestructive and highly sensitive manner. Herein, we introduced a bioactive laser approach for ultrasensitive and real-time monitoring of intracellular redox reactions. Resazurin, as a popular cell viability assay reagent, has lasing behaviors and photostability, which makes it suitable for the development of bioactive lasers. Due to the strong interactions of light and matter within the laser cavity, subtle changes in resazurin concentration during the redox reaction can be translated into detectable wavelength shifts in the lasing spectrum. With narrow laser peaks, the sensing resolution can reach down to 30 pM per 10 pm wavelength shift. Combined with a scanning platform, we mapped the intracellular and intercellular heterogeneities in metabolism. Further applications in cell identification, oxidative stress assessment, and drug evaluation revealed the universal applicability of this method in cell assays and biomedical analysis, providing insights into disease diagnosis and drug screening.