I'm doing a western blot with biotinylated antibodies. Everything worked fine until 2 months, a black background appeared on handling with strepta-poly-HRP.
My typical protocol: PVDF membrane, saturation 1 at 2 hours with blocker, hybridization with my biotinylated Ac 2h at 0.5 μg / mL, washes, hybridization with strepta poly hrp at 1:40 000 for 20 min, ECL western blot reagent .
We have done many tests with many different parameters: 7 different blockers, buy a new ECL, new batch of Strepta-poly-HRP + new reference + new concentration, new membrane including nitrocellulose test, with / without antibodies...
I have no idea to solve my problem (I don't have it with direct couplings), If you have hypothesis, don't hesitate.
Thank you very much,