Mixed Focused UltraSound (FUS) / fluorescence imaging platform for characterization of the spatial-temporal dynamics of FUS-evoked calcium fluxes in an in vitro human cell model

Focused UltraSound (FUS) could offer a promising, minimally-invasive and targeted alternative to standard neurostimulation strategies. The study of FUS-modulated Ca2+ mobilization is essential for describing intercellular signaling across neuronal networks. In this work, the spatial and temporal characteristics of Ca2+ fluxes triggered by FUS were investigated in vitro on a mixed FUS / fluorescence microscopy platform. Experiments were performed on human neural progenitors, loaded with a Ca2+ -sensitive fluorescent dye. Single FUS pulses were applied and resulting neural activities were recorded using fluorescence imaging. Ca2+ dynamics produced by FUS were compared to those obtained by chemical and mechanical stimulation. The localization of the response and the speed of propagation across the neural network were investigated. The results of this study underline that FUS-stimulated Ca2+ fluxes are transient and capable of being transmitted across several interconnected neurons. Overall, the complex data obtained using this mixed platform should be crucial for improving current knowledge and control of FUS neurostimulation phenomena.