The development of fluorescent molecular sensors for imaging voltage changes in biological systems has revolutionized neuroscience, providing a tool to capture neuronal activity over large areas with sub-neuron resolution both in vitro and in vivo [1–3]. However, the poor photostability of molecular voltage sensors limits recording times to a few minutes [1–3], posing problems for longitudinal studies of network evolution and disease processes. Here, we present an alternate non-invasive platform for sensitive high resolution voltage imaging using fluorescent, charge-sensitive defects in a transparent diamond substrate [6]. Using these charge state sensors, we establish an all-optical diamond voltage imaging microscope (DVIM) capable of sub-millisecond voltage imaging with sub-millivolt sensitivity. Our work open new pathways for the study of 2D neuronal network cultures as well as 3D brain organoids.
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