PT  - JOURNAL ARTICLE
AU  - Pisfil, Mariano Gonzalez
AU  - Nadelson, Iliya
AU  - Bergner, Brigitte
AU  - Rottmeier, Sonja
AU  - Thomae, Andreas W.
AU  - Dietzel, Steffen
TI  - Stimulated emission depletion microscopy with a single depletion laser using five fluorochromes and fluorescence lifetime phasor separation
AID  - 10.1101/2022.04.13.487856
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2022.04.13.487856
4099  - http://biorxiv.org/content/early/2022/04/13/2022.04.13.487856.short
4100  - http://biorxiv.org/content/early/2022/04/13/2022.04.13.487856.full
AB  - Stimulated emission depletion (STED) microscopy achieves super-resolution by exciting a diffraction-limited volume and then suppressing fluorescence in its outer parts by depletion. Multiple depletion lasers may introduce misalignment and bleaching. Hence, a single depletion wavelength is preferable for multi-color analyses. However, this limits the number of usable spectral channels. Using cultured cells, common staining protocols, and commercially available fluorochromes and microscopes we exploit that the number of fluorochromes in STED or confocal microscopy can be increased by phasor based fluorescence lifetime separation of two dyes with similar emission spectra but different fluorescent lifetimes. In our multi-color FLIM-STED approach two fluorochromes in the near red (exc. 594 nm, em. 600-630) and two in the far red channel (633/641-680), supplemented by a single further redshifted fluorochrome (670/701-750) were depleted with 775 nm. To the best of our knowledge, these are the first published five color STED images. Generally, this approach doubles the number of fully distinguishable colors in laser scanning microscopy. We provide evidence that eight color FLIM-STED with a single depletion laser would be possible if suitable fluorochromes were identified and we confirm that a fluorochrome may have different lifetimes depending on the molecules to which it is coupled.Competing Interest StatementThe authors have declared no competing interest.