Multi-photon, label-free photoacoustic and optical imaging of NADH in brain cells

In a new paper published in Light: Science & Applications, a team of scientists, led by Professor Peter T. C. So from Department of Mechanical Engineering, Massachusetts Institute of Technology, United States and co-workers have developed a novel label-free, multiphoton photoacoustic microscope (LF-MP-PAM) that leverages a near-infrared femtosecond laser to detect endogenous NAD(P)H, a key metabolic coenzyme involved in cellular energy production and redox balance during neuronal activity. This pioneering approach overcomes the depth limitations of conventional optical imaging of NADH, which is typically restricted to approximately 100 μm due to the strong absorption of near-ultraviolet fluorescence. By utilizing photoacoustic detection of three-photon excitation of NAD(P)H, the researchers have achieved remarkable imaging depths—reaching up to 700 μm in brain slices and an impressive 1100 μm in cerebral organoids. These depths far exceed those achievable with traditional fluorescence microscopy, opening new possibilities for in-depth, high-resolution imaging of brain metabolism. This is a groundbreaking technique for non-invasively detecting biological events in the brain at single-cell resolution and we expect it will have profound implications for both medical diagnostics and neuroscience research.

 

This method enables real-time monitoring of metabolic dynamics in brain cells, offering invaluable insights into neurodevelopment, disease mechanisms, and neuronal function. The study also validated the technique's effectiveness in living cells, demonstrating its ability to detect metabolic shifts in HEK293T and HepG2 cells. By integrating simultaneous photoacoustic and optical imaging, this innovation provides a powerful tool for visualizing brain metabolism with unprecedented clarity and precision.

 

The implications of this breakthrough extend across multiple domains of neuroscience and medicine. Researchers anticipate that this technology could transform the study of neurodegenerative disease such as Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis (ALS), and neurodevelopmental disorder such as Rett Syndrome, as well as enhance our understanding of fundamental brain functions. Moreover, its non-invasive nature holds significant promise for clinical applications, potentially allowing clinicians to track brain health, monitor disease progression, and assess treatment efficacy with unparalleled accuracy.

 

This revolutionary imaging approach represents a major step forward in biomedical research, paving the way for new discoveries in brain function, pathology, and personalized medicine. As the technique continues to evolve, it may soon become an indispensable tool for both scientific exploration and clinical intervention, bridging critical gaps in our ability to study and treat neurological conditions.

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