Excite
A focused excitation beam creates a diffraction-limited fluorescence volume.
STED protocol notes
Protocols
A first-pass guide for samples, labels, controls, and imaging workflow on inverted STED systems.
STED in plain terms
STED makes the emitting spot smaller.
Stimulated emission depletion microscopy starts like a confocal scan: an excitation spot brings fluorophores into an excited state. A second, red-shifted depletion beam is shaped like a doughnut and overlapped with that spot. Around the edge of the spot, the depletion beam drives excited fluorophores back down before they fluoresce. The center of the doughnut is left dark, so only a smaller central region emits.
Deplete
A matched depletion beam suppresses fluorescence around the edge of that spot.
Scan
The smaller effective emission spot is raster scanned to build the image.
Balance
Resolution improves with depletion intensity, but signal, bleaching, and sample health set the practical limit.
Sample preparation
Baseline fixed-cell STED preparation.
The exact chemistry depends on the biology, antibody, dye, and facility rules. This starter path keeps the sequence clear.
- Define the structure and expected scale. Pick one target with a known nanoscale feature, such as microtubules, nuclear pore complexes, membrane-associated structures, or a validated bead slide.
- Choose an STED-suitable label before staining. Match excitation, emission, detection window, and depletion wavelength. Bright confocal dyes are not automatically good STED dyes.
- Preserve structure first. Select fixation, permeabilization, and blocking around the target. STED will reveal preparation artifacts that confocal imaging can hide.
- Keep the coverslip clean and compatible. Use high-quality glass, keep the specimen from drying, and avoid mounting formats that introduce aberration into a high-NA inverted objective.
- Reduce nonspecific background. Wash thoroughly, tune blocking, and avoid over-labeling. Background consumes signal budget and can mask the gain from the depletion beam.
- Mount and image promptly. Some fixed STED samples age quickly. Log the mounting medium, storage condition, and imaging date so performance can be repeated.
Rule:
If the confocal image is dim, nonspecific, saturated, or structurally questionable, STED will usually make the problem
easier to see rather than easier to solve.
Fluorophores
Dye choice is part of the system.
STED labels need brightness, photostability, efficient depletion, and spectral compatibility with the instrument. Families commonly used in STED workflows include Abberior STAR dyes, ATTO dyes, selected Alexa Fluor variants, SiR dyes, and other organic fluorophores, but compatibility depends on the exact excitation and depletion wavelengths.
Decision
What to check
Why it matters
Depletion match
The dye can be depleted by the system wavelength without adding avoidable excitation background.
A mismatch gives weak resolution gain or excess background.
Photostability
The label tolerates the planned dwell time, averaging, and depletion power.
Bleaching can erase fine structure before the scan finishes.
Labeling distance
Primary/secondary antibodies, nanobodies, tags, or direct conjugates are sized appropriately.
Large labels can offset the apparent structure by more than the resolution gain.
Mountant
The dye remains bright and stable in the chosen mounting medium.
Mountants can change brightness, bleaching behavior, and background.
Acquisition workflow
Move from confocal to STED carefully.
The first acquisition should be deliberate: find a good region in confocal mode, avoid saturation, then add depletion power gradually while watching signal, resolution, bleaching, and artifacts.
Find the region in confocal mode
Use low exposure and moderate scan settings to locate the sample, focus at the coverslip side, and confirm specificity.
Set detection without saturation
Keep bright pixels below clipping so the STED comparison is meaningful and quantitative enough for commissioning.
Turn on depletion carefully
Increase depletion power in small steps. Stop when resolution gain is useful, not simply when the power is higher.
Match pixel size to the target
Use smaller pixels than confocal imaging so the super-resolved point spread function is sampled adequately.
Control dwell and averaging
Trade scan speed, dwell time, line averaging, and frame accumulation against bleaching and drift.
Save paired views
Capture confocal and STED images of the same field with logged settings for comparison and later troubleshooting.
Validation
Controls make the result interpretable.
Same-field confocal comparison
Acquire a matched confocal image before or after STED so the resolution improvement is visible in the same biology.
Single-color controls
Use them to check bleed-through, depletion cross-effects, and channel-specific background.
Bead or reference slide
Keep a reproducible optical sample for alignment, point spread function checks, and installation acceptance.
Biological negative and positive controls
Confirm that the structure is real and the expected labeling pattern is present before interpreting nanoscale detail.
Troubleshooting
Common first-session failure modes.
Symptom
Likely cause
First response
No visible resolution gain
Dye/depletion mismatch, low depletion power, poor alignment, or sample structure too sparse.
Confirm dye compatibility, run a reference slide, and compare same-field confocal/STED images.
Fast bleaching
Too much depletion power, high dwell time, unstable dye, or mountant incompatibility.
Lower power and dwell, reduce repeats, and test a more photostable label or mountant.
High background
Nonspecific labeling, autofluorescence, excess antibody, or out-of-focus signal.
Improve blocking and washing, simplify channels, and check unlabeled controls.
Ringing or hollow structures
Over-depletion, aberration, drift, or a sample that moved during the scan.
Back off power, check coverslip/mounting, shorten scans, and verify with beads.
Drift between frames
Mounting instability, thermal drift, live-sample motion, or slow acquisition.
Let the system equilibrate, improve sample mounting, and reduce frame time.
Reading list
Suggested reading.
Recent review and protocol papers for STED sample preparation, fluorophore choice, acquisition, validation, and artifacts.
- Gražvydas Lukinavičius, Jonatan Alvelid, Rūta Gerasimaitė, Carmen Rodilla-Ramirez, Văn Thắng Nguyễn, Giuseppe Vicidomini, Francesca Bottanelli, Kyu Young Han, Ilaria Testa. Stimulated emission depletion microscopy. Nature Reviews Methods Primers, 4, 56, 2024. doi:10.1038/s43586-024-00335-1.
- Jan Tønnesen, Ulrike V. Nägerl, Will Jahr. Superresolution imaging for neuroscience: STED microscopy and practical performance considerations. Methods, 2019/2020. doi:10.1016/j.ymeth.2019.07.019.
- Alshafie and Stroh. Multicolor STED microscopy sample preparation. In Methods in Molecular Biology, 2022. doi:10.1007/978-1-0716-2051-9_15.
- Antonicka et al. A fixed-cell mitochondrial STED microscopy protocol. Methods in Enzymology, 2024. doi:10.1016/bs.mie.2024.07.052.
- Arizono et al. Live STED imaging for functional neuroanatomy. Nature Protocols, 2025. doi:10.1038/s41596-024-01132-6.
- Dasgupta et al. Photoconversion artifacts in STED microscopy. Nature Methods, 2024. doi:10.1038/s41592-024-02297-4.
- Sezgin et al. STED-FCS in living cells: protocol and analysis. Nature Protocols, 2019. doi:10.1038/s41596-019-0127-9.
Next step
Turn a protocol into an instrument plan.
Share the sample, microscope geometry, and resolution goal. Peregrine can scope a module, custom inverted microscope, or pilot.