Image-iT™ FX Signal Enhancer - FAQs

The Image-iT FX Signal Enhancer reduces non-specific binding of dye conjugates by blocking positively-charged areas of cells or tissues that attract negatively-charged dyes. In cells after fixation, some positively-charged structures are the nuclei and mitochondria. Thus, you would expect to see a reduction in both mitochondrial and nuclear signal. The lower signal you see afterward is the specific mitochondrial signal; the fluorescence that was lost was the non-specific labeling.

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No. Image-iT FX Signal Enhancer is not a protein blocker, like BSA, normal serum, or other commercial antibody blockers. Use it as a separate step to block non-specific charge-based binding of dyes to cellular components.

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This is most likely charge-based binding due to interactions of the charge on the dyes with cellular components of opposite charge. This can be blocked by using the Image-iT FX Signal Enhancer Solution which eliminates non-specific binding due to charge. The Signal Enhancer is applied as a pre-blocking step and your regular blocking regimen should be used to limit non-specific binding due to protein-protein interactions. Signal Enhancer cannot be used on live cells.

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The click reaction is very selective between an azide and alkyne. No other side reactions are possible in a biological system. Any non-specific background is due to non-covalent binding of the dye to various cellular components. The Select FX Signal Enhancer is not effective at reducing non-specific charge-based binding of dyes following the click reaction; we do not recommend its use with the Click-iT detection reagents. The best method to reduce background is to increase the number of BSA washes. You should always do a no-dye or no-click reaction control under the same processing and detection conditions to verify that the background is actually due to the dye and not autofluorescence. You can also perform the complete click reaction on a carrier solvent-only, no EdU or no-EU control to verify the specificity of the click reaction signal.

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A blocking step should be performed to reduce fluorescence due to non-specific antibody binding. A common blocking step is the addition of a 2-5% solution of bovine serum albumin (fraction V defatted BSA). Another approach employs the addition of a 5-10% solution of serum from the species in which the secondary antibodies were raised. For example, when using goat anti-mouse IgG secondary antibodies, samples may be effectively blocked with 5-10% normal goat serum. To further reduce background fluorescence, the Image-iT FX Signal Enhancer can be included as a pre-blocking step to decrease non-specific labeling due to charge interactions between the dyes on the conjugates and the cellular constituents.
If you are using a secondary antibody make sure that the species of the antibody is not the same as the species of the sample. For example do not use an anti-mouse secondary antibody on mouse tissue.
Titrate the antibody to the lowest concentration you can use and still get adequate signal.
Try using a fluorescently tagged primary antibody because it should give reduced background but be aware this can reduce signal intensity.

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What may be happening is non-specific binding of the secondary antibody due to dye charge, for example, where the negatively-charged dye is attracted to positively-charged cellular components. To block this, use Image-iT FX Signal Enhancer (Cat. Nos. I36933 and R37107), which blocks non-specific binding due to charge interactions between the dyes on conjugates and cellular components.

Find additional tips, troubleshooting help, and resources within our Cell Analysis Support Center.