Bovine Serum Albumin – a Help or Hindrance in Immunoassays

By on March 31, 2011

Immunoassays are an important part of medical diagnosis. They are valuable tools that can detect substances such as chemicals, bacteria, and viruses in biological fluid samples. With a simple urine or blood test doctors have at their disposal hundreds of immunoassays that can detect the presence of illegal drugs, dangerous viruses, or hormones for pregnancy tests, just to name a few. It is critical that immunoassays function without false positive or inconsistent results due to the serious nature of these tests.

Designing reliable and consistent immunoassays is a challenge. Immunoassays utilize the relationship between antibodies and their antigens to detect the presence of the substance they are testing for. It is essential that the antibodies and antigens bind together and not with any other substances. Non-specific binding, binding that is not antibody to antigen, is a big problem because it can cause false positives – something no patient would appreciate. It is also important to keep the proteins or biomarkers being used stable so that proper binding can take place and provide consistent results.

Scientists frequently use Bovine Serum Albumin (BSA) to address both the issue of non-specific binding and stability. When BSA is added to an immunoassay it binds to sites where there is potential for non-specific binding without interfering with antibody/antigen binding. An added bonus of using BSA is that it stabilizes proteins while in solution.

While BSA can sometimes be used successfully, there are many times when BSA can create failures in assays. There are several possible explanations as to why these failures occur, but most often the reason is assay dependent. In their quest to develop the most accurate immunoassays possible, scientists have identified several problems that occur with the use of BSA including: denaturation or protease activity that destroys the proteins/biomarkers, instability in the assay also compromising protein integrity, inconsistent results, and non-specific binding when IgG is present in the BSA.

Why does BSA cause these failures? Several theories exist to explain assay failures, but what it really seems to come down to is BSA’s inconsistency as a product both in batch-to-batch variation and variation between manufacturers. There can be animal component contamination, variation in the processing methods and maybe the most basic, variations found in different herds.

All this begs the question – is there a better way to get the benefits of BSA without the potential failures? Using a recombinant, animal-free albumin in immunoassays could accomplish that. It would eliminate animal component contamination and batch-to-batch inconsistencies by providing a high-quality, consistent product every time. It would also remove the need for costly IgG free BSA because an animal-free albumin contains no IgG at all. In addition to the assay benefits, animal-free products would also remove any safety handling concerns identified with animal blood products containing viruses or prions. It also eases regulatory issues by eliminating any animal components that have to be imported and properly documented. Recombinant albumin can provide the help without the hindrance.

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