We demonstrate fluorescence imaging by two-photon excitation without scanning in biological specimens as previously described by Hwang and co-workers, but with an increased field size and with framing rates of up to 100 Hz. During recordings of synaptically-driven Ca2+ events in primary rat hippocampal neurone cultures loaded with the fluorescent Ca2+ indicator Fluo-4 AM, we have observed greatly reduced photo-bleaching in comparison with single-photon excitation. This method, which requires no costly additions to the microscope, promises to be useful for work where high time-resolution is required.
Amor, R., McDonald, A., Trägårdh, J., Robb, G., Wilson, L., Abdul Rahman, N. Z., ... McConnell, G. (2016). Widefield two-photon excitation without scanning: live cell microscopy with high time resolution and low photo-bleaching. PLOS One, 11(1), . https://doi.org/10.1371/journal.pone.0147115