Quantitative assessment of bovine serum albumin proteins for blocking applications

Bovine serum albumin (BSA) is one of the most widely used protein reagents in the scientific community, especially for surface passivation ("blocking") applications in various bioassays. Numerous BSA protein options are commercially available, however, there is scarce information about which ones are preferable for blocking applications. Herein, we conducted biophysical and bioassay measurements to quantitatively compare the conformational, adsorption, and blocking properties of BSA protein reagents that were obtained through six purification methods. Depending on the method, there were significant differences in the conformational and adsorption properties of BSA proteins, mainly due to the presence of fatty acid stabilizers. In turn, we discovered that fatty acid-free BSA proteins exhibit superior blocking performance to fatty acid-stabilized BSA proteins in surface- and nanoparticle-based bioassays. We critically discuss mechanistic factors behind these performance variations and our findings offer a practical framework to guide BSA selection for blocking applications.