Locate background with controls
Unstained samples reveal autofluorescence. Fluorescent-streptavidin-only samples reveal background associated with endogenous biotin or adsorption. A matched workflow omitting the biotinylated probe helps assess upstream reagents. Acquire these controls under the same settings as the complete stain.
Retain target signal during troubleshooting
Keep upstream probe conditions fixed while comparing streptavidin amount, blocking or washing separately. Track positive targets and negative regions. Lower background accompanied by loss of target signal does not establish better detection.
Use probe-omission controls
A control lacking the biotinylated primary antibody or probe can still show endogenous-biotin signal. Follow the specified sequence and washing steps for a biotin-blocking workflow; residual biotin can also consume subsequently added fluorescent streptavidin.