In contrast to conventional linear fluorescence microscopy, the nonlinear character and the longer excitation wavelength in multi-photon microscopy offer several advantages: (i) larger probing depth (ii) lower phototoxicity and reduced photodamage.
Both advantages make two-photon-fluorescence microscopy an ideal choice for the direct spatiotemporal visualization of neurons and neuronal activity in living animals. The key fluorescent proteins for such experiments are green and red fluorescent proteins that can be excited by two-photon absorption at 920nm and 1050nm, respectively. The clear requirements in terms of wavelength, pulse duration, and output power make TOPTICA's easy-to-use and fully integrated fiber lasers FemtoFiber ultra 920 at 920nm and FemtoFiber ultra 1050 at 1050nm the perfect choice for two-photon experiments in neuroscience.
To understand the potential and latest trends in two-photon fluorescence microscopy in neuroscience please watch the webinar with Dr. Weijian Zong from the Moser lab in Trondheim, pioneering the field of miniaturized two-photon microscopy:
Two-Photon Optogenetics in Neuroscience
All-optical interrogation is a novel approach to understand how active patterns in neuronal activity drive behavior. In such experiments the visualization of neuronal activity by two-photon imaging is combined with two-photon optogenetics to stimulate individual neurons by photoactivation of channelrhodopsins within the cell.
With the need of exciting many neurons in parallel, the laser requirements and microscopy technology for two-photon optogenetics are fundamentally different from two-photon imaging. Typically, high-power multi-Watt lasers at 1030 - 1040 nm with repetition rates in the 100 kHz - 1 MHz range are used in combination with a spatial light modulator (SLM) to excite 10 s to 100 s of neurons simultaneously. Such lasers ideally offer integrated power control and dispersion precompensation to optimize two-photon excitation efficiency.
TOPTICAs FemtoFiber vario 1030 HP has been fully optimized to perfectly match these requirements and, together with the FemtoFiber ultra 920, complements TOPTICA's product offering for all-optical interrogation experiments in neuroscience.