Monitoring the Oxygen Dynamics of Brain Tissue In Vivo by Fast Acousto-Optic Scanning Microscopy: A Proposed Instrument.

The function of the brain neural circuit is highly dependent on oxygen supply. Imaging the precise oxygen distribution and dynamics are critical for understanding the relationship between neuronal activity and oxygen dynamics of the nearby capillaries. Here, we develop fast acousto-optic scanning two-photon microscopy. Combined with oxygen probes, such as PtP-C343, we can monitor oxygen dynamics at the submicron level by this real-time microscopy. In this fast acousto-optic scanning microscopy, an acousto-optic deflector (AOD), an inertia-less scanner, is used to scan the femtosecond laser. A cylindrical lens is used to compensate the 'cylindrical lens effect' of AOD and a prism is used to compensate the chromatic dispersion of AOD. An electro-optical modulator (EOM) and a sCMOS camera are gated to measure the phosphorescence lifetime. With a 40× water objective lens, this set-up can image a 100 μm × 100 μm field of view at a speed of 20 frames per second and a 25 μm × 8 μm field of view at a speed of 500 frames per second. This real-time two-photon microscopy is expected to be a good tool for observing and recording the precise rapid oxygen dynamics in the cerebral cortex, which will facilitate studies of oxygen metabolism in neurosciences.