A Multi-Chemical Image Sensor for Simultaneous Visualization of Lactate and pH Distribution and its Application for Extracellular Measurement of a Hippocampal Slice

Simultaneous high-resolution imaging of lactate emission and hydrogen ions (H+), which are required for long-term memory formation, will aid in the elucidation of memory formation mechanisms based on the analysis of neurotransmission mechanisms. In this paper, we report the world's first $6-\mu \mathrm{m}$ -pitch multi-chemical image sensor that can concurrently visualize the emission of lactate and H+ with an Au/Ti layer patterned on a $2-\mu \mathrm{m}$ -pitch, $256\times 256$ -pixel pH image sensor. This sensor can simultaneously acquire the dynamics of two different chemicals, lactic acid and H+, in real time while maintaining spatiotemporal information. The conventional method for extracellular lactate imaging is magnetic resonance spectroscopic imaging (MRSI), but it has a low spatiotemporal resolution (on the order of several millimeters or seconds). In addition, visualization and analysis of lactate distribution with a spatial resolution of several micrometers has not been realized yet. On the contrary, our novel multi-chemical image sensor can be used to visualize the spatiotemporal dynamics of local lactate and pH distributions for single-cell analysis.