These blocking buffers are 10% (w/v) solutions of high-quality BSA that are useful for saturating excess protein-binding sites on membranes and microplates in immunoassays. Blocker BSA Buffers are most frequently diluted 10-fold (to 1% BSA) for initial testing, but other buffer concentrations can be beneficial for specific systems. BSA is usually more effective than nonfat milk blocking buffers for biotin-avidin systems because it contains a single purified protein that is devoid endogenous biotin.

The purpose of the blocking step in an assay is to improve assay sensitivity by reducing background interference. However, unforeseen cross-reaction of detection reagents with blocking buffers is itself a cause of high background and low signal-to-noise ratios in assay systems. Because individual blocking buffers are not compatible with every system, a variety of blockers in both Tris-buffered saline (TBS) and phosphate-buffered saline (PBS) are available. The best blocking buffer for a specific experiment will bind to all potential sites of nonspecific interaction, eliminating background without altering or obscuring the epitope for antibody binding.

To optimize the blocking step for a particular immunoassay, empirical testing is essential. Using inadequate amounts of blocker will result in excessive background. Using an excessive blocker concentration can mask antibody-antigen interactions or inhibit the marker enzyme. For best results when developing a new immunoassay, test several different blocking agents for the highest signal-to-noise ratio in the assay. There is no single blocking agent that is ideal for every occasion because many factors can influence nonspecific binding, including various protein interactions unique to a specific assay system.

Features and Benefits:
‧ Purified protein – 10% solutions of high-quality bovine serum albumin; a single purified protein provides fewer chances of cross-reaction with assay components than serum or milk solutions
‧ Convenient – concentrated formulation saves storage space and can be diluted easily to obtain optimal blocking results for specific applications
‧ Easy to use – no waiting for powder to dissolve with this ready-to-dilute liquid concentrate
‧ Flexible – available in PBS and TBS formulations to suit a variety of applications