Aurion incubation solution additive AURION BSA-c™, unique incubation buffers additive with an unparalleled ability to effectively prevent charge-based background. BSA-c™ are prepared by acetylation of bovine serum albumin (BSA). Polycationic sites in the specimen interact readily with negatively charged acetylated BSA molecules. This significantly reduces the risk that such sites might bind negatively-charged immunoreagents and immunogold conjugates and thus reduces the risk of background.

AURION BSA-c™ buffers suppresses background competitively with little or no effect on the specific reaction. Its successful application is not limited to immunogold detections, but it is equally efficient in fluorescent and enzyme-based detection systems. AURION BSA-c™ concentrations as low as 0.01 to 0.1% inhibit binding of gold conjugate to polycationic poly-l-lysine coated grids almost completely (>99%).

In the blocking step, hydrophobic moieties causing stickiness in the specimen surface are rendered hydrophilic to minimize background. The more dynamic charge-based interaction between the specimen surface and immunoreagents also needs to be controlled to eliminate background.

The surface properties of the specimen can be simplified by division into four compartments. They are negatively charged (polyanions, proteins, especially after aldehyde fixation, lipids), neutral (0) and positively charged (histone proteins, polycations) and H hydrophobic (lipids, fat droplets, resins). After an appropriate blocking step these areas are covered with blocking compounds.

In low ionic strength media negatively charged antibodies and gold conjugates are repulsed by negatively charged specimen areas which frequently may contain the antigens to be detected. Background does not likely occur in such areas. The positively charged areas attract antibodies and gold conjugates potentially leading to background. In a moderate ionic strength incubation solution, repulsion and attraction are diminished due to the presence of ions. The negatively charged BSA-c™ competes with the negatively charged antibodies and gold reagents for non-specific binding to the positively charged specimen compounds, thus reducing background to the greatest possible extent without interfering with antigen detection.