Label-Free Real-Time Imaging of Extracellular Lactate From a Hippocampal Slice Based on Charge-Transfer-Type Potentiometric Redox Sensor Arrays

Medically important real-time imaging of extracellular lactate and its spatiotemporal analysis has not yet been achieved. If it could be successfully realized, it would help clarify the function of physiological neurotransmission and drug discovery based on glial cell neuron lactate transport. To this end, we fabricated a 40 μm pitch, 128 × 128 pixel redox-type label-free lactate image sensor based on a potentiometric hydrogen peroxide (H
₂
O
₂
) sensor array and successfully obtained a diffusion image of lactate. Further, the fabricated sensor was applied to extracellular imaging of tissue from a mouse hippocampus. A 300-μm-thick slice of the hippocampus was placed on a lactate image sensor, and when stimulated by glutamate, the output image of the sensor changed dynamically. The output voltage change (ΔV
_Out
) of the sensor was approximately 140 mV. Conversely, verification by a comparative experiment using an enzyme-free sensor confirmed a significant difference in the value of ΔV
_Out
. It can thus be concluded that the observation of lactate in solution was demonstrated successfully by label-free real-time imaging of lactate from mouse hippocampus tissue with glutamate stimulation on a 40 μm-pitch sensor array.