I am attempting to use the following patent to prepare a variety of immunoassay reagents.
Microparticle immunoassay reagents, sensitive and specific immunoassay reagents and immunoassay methods using these reagents
EP 0679892 B1
We bind carrier protein (HSA or RSA) linked to our small molecule analyte to the particles, then use analyte specific rabbit polyclonal AB to agglutinate particles. Small molecule analyte in the sample competes for AB thus preventing agglutination (negative curve).
Reaction size is 150uL sp size is 3uL OD is read at 600nm, Chemistry Analyzer AU480
When we run the assay with small molecule analyte standards in PBS buffer everything works well we get a good curve. However even a small amount of human serum in the reaction completely blocks agglutination of particles.
Made up Example:
Analyte ug/mL vs OD using PBS buffer as base:
0 = 0.00
1 = -0.05
2 = -0.10
4 = -0.20
8 = -0.40
Analyte ug/mL vs OD using Negative serum as base:
0 = -0.35
1 = -0.35
2 = -0.35
4 = -0.35
8 = -0.35
Please let me know if you have any suggestions, I can't find any literature that shows matrix interference this strong.