smFISH probes are sequence-defined oligonucleotide sets for precise single-RNA detection, enabling transcript quantification and spatial localization in cells and tissues.
smFISH probes are short fluorescently labeled oligonucleotides used in coordinated probe sets to detect individual RNA molecules by single-molecule fluorescence in situ hybridization. Unlike bulk hybridization methods that report averaged signal, smFISH is designed to visualize and count discrete transcript molecules in fixed cells or tissues.
A typical smFISH assay uses multiple oligonucleotides per transcript target, each hybridizing to a different region of the same RNA. When enough probes bind, the combined fluorescence signal appears as a bright diffraction-limited spot corresponding to a single RNA molecule. This makes smFISH especially useful for transcript counting, cell-to-cell variability analysis, and intracellular RNA localization studies.
Because smFISH depends on both sequence specificity and cumulative signal generation, probe-set design is as important as fluorophore choice. Probe number, tiling density, transcript accessibility, labeling strategy, and imaging configuration all contribute to final assay performance.
An smFISH experiment usually uses many short probes targeting the same RNA, each carrying a fluorophore or readout-compatible labeling strategy.
smFISH visualizes individual transcripts as diffraction-limited fluorescent spots after multiple labeled probes bind the same RNA target.
smFISH relies on dozens of probes binding a single RNA to generate a detectable fluorescent spot.
Each probe targets a unique region of the transcript, minimizing off-target binding.
smFISH preserves intracellular RNA localization at subcellular resolution.
Fluorescent labeling is central to smFISH performance because signal intensity depends on the combined optical output of the entire probe set. Probe sets may be built with directly labeled oligonucleotides or with more modular readout approaches depending on the complexity of the experiment.
Dye selection should consider microscope configuration, spectral overlap, and sample autofluorescence. Red and far-red dyes (e.g., Cy5, Quasar 670) typically provide higher signal-to-noise in biological samples.
Quantify transcript molecules cell by cell rather than relying on population averages.
Map where RNAs reside inside cells or tissues to study trafficking and compartmentalization.
Measure expression variability across individual cells with high spatial context.
Confirm transcript presence and localization identified by bulk or single-cell sequencing workflows.
A representative smFISH workflow progresses from target selection and probe-set design to fluorescent labeling, hybridization, imaging, and spot-based RNA analysis.
smFISH, seqFISH, and MERFISH all use synthetic oligonucleotide hybridization for RNA imaging, but they differ in complexity, multiplexing strategy, and decoding logic.
Signal depends on the number of probes that can bind the same RNA molecule.
Secondary structure and bound proteins can affect probe binding.
Brightness and photostability influence spot detection quality.
Sequential hybridization probe systems for multiplexed RNA imaging and spatial transcriptomics workflows.
Barcoded oligonucleotide probe libraries for error-robust multiplexed RNA imaging.
Custom fluorophore-labeled oligos for smFISH, FISH, imaging, and readout probe workflows.
smFISH probes are fluorescent oligonucleotide sets used to detect individual RNA molecules with high specificity and single-molecule sensitivity.
They are used for single-molecule transcript counting, RNA localization, and spatial gene expression analysis.
smFISH often uses multiple probes per transcript target, commonly dozens, to generate detectable single-molecule signal.
Yes. Multiplexing can be achieved through multiple fluorophores, spectral separation, or more advanced sequential or barcoded strategies.
Yes. smFISH is commonly used to validate transcript abundance and localization suggested by sequencing experiments.
For the fastest quote, share the target transcript, species, imaging format, preferred dye or channel plan, and whether you need a standard smFISH probe set or a more multiplex-ready architecture.
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