2016
In Multiphoton Microscopy in the Biomedical Sciences XVI (Vol. 9712)

ns-time resolution for multispecies STED-FLIM and artifact free STED-FCS

Authors:

Koenig, M., Reisch, P., Dowler, R., Kraemer, B., Tannert, S., Patting, M., ... & Erdmann, R.

Keywords:

super-resolution, STED, gSTED, FCS, FLCS, TCSPC, pulsed interleaved excitation, PIE, supported lipid bilayers

Abstract:

Stimulated Emission Depletion (STED) Microscopy has evolved into a well established method offering optical superresolution below 50 nm. Running both excitation and depletion lasers in picosecond pulsed modes allows for highest optical resolution as well as fully exploiting the photon arrival time information using time-resolved single photon counting (TCSPC). Non-superresolved contributions can be easily dismissed through time-gated detection (gated STED) or a more detailed fluorescence decay analysis (FLIM-STED), both leading to an even further improved imaging resolution. Furthermore, these methods allow for accurate separation of different fluorescent species, especially if subtle differences in the excitation and emission spectra as well as the fluorescence decay are taken into account in parallel. STED can also be used to shrink the observation volume while studying the dynamics of diffusing species in Fluorescence Correlation Spectroscopy (FCS) to overcome averaging issues along long transit paths. A further unique advantage of STED-FCS is that the observation spot diameter can be tuned in a gradual manner enabling, for example, determining the type of hindered diffusion in lipid membrane studies. Our completely pulsed illumination scheme allows realizing an improved STED-FCS data acquisition using pulsed interleaved excitation (PIE). PIE-STED-FCS allows for a straightforward online check whether the STED laser has an influence on the investigated diffusion dynamics.