Has anyone experienced peptide absorption in the blank plasma when using an ELISA kit? If so, what could be the possible reasons for this problem, and what strategies or techniques were employed to successfully address this issue?
I think you're saying you're getting an unacceptably high background reading from your negative control. It's good that you're concerned about this problem. It is common, especially for human blood samples.
If you are using human blood, be sure to take proper bloodborne pathogen precautions, including your vaccinations and PPE.
Consider using serum rather than plasma. And for human samples you should heat the sera to kill viruses.
You should be diluting your samples in blocker solution. For ELISA you probably can start with a 1:1000 dilution and work toward 1:1000000.
You can reduce non-specific binding by adding things to your blocker solution. Starting with a base of PBS, blockers usually contain a protein like casein or albumin at 0.1% (1 mg/mL) and a nonionic detergent like Tween at 0.01%. You can try using a different protein. You can safely increase the protein 10-fold. Depending on the ELISA format, you may want to include 1% control serum in your diluent and blocker as a blocker protein. Increasing the detergent (up to 10x) may decrease your overall signal, but it may increase signal/noise ratio. And sometimes it helps to add 0.1M glycine.
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