I will present a Light-sheet fluorescence microscope (LSFM) for fast volumetric imaging during extended periods of time. In this case, the observation arm of the microscope contains an electrically tunable lens (ETL) that is used to shift the focal position of the collection lens. By moving the light sheet plane in synchrony with the ETL, it is possible to scan the full 3D sample, which remains totally static, at high speeds (25 volumes/s) .
This system is used to image the spontaneous Ca2+ activity, as reported by GCaMP fluorescence, in 3D of primary neuron cultures in hydrogels. The field of view is of 300µm x 300µm x 1mm. The imaging speeds allows a proper sampling of the propagation of GCaMP signal in the full observation volume . The obtained data is then processed to calculate the connectivity maps in the 3D neuron cultured in hydrogels.