Streptavidin-Response Curves for Biotinylated Magnetic Nanoparticles Suspended in 1x Phosphate Buffered Saline, 1 Micro Molar Bovine Serum Albumin, and 1 Micro Molar Monomeric Streptavidin

The streptavidin-biotin bond has a k_off of ~10^-6 1/s, while the SavPhire monomeric streptavidin-biotin bond has a k_off of ~10^-5 1/s. Wherein bond strength is inversely proportional to k_off. We assume the bovine serum albumin (BSA)-biotin bond has a k_off several orders of magnitude larger than the k_off for monomeric streptavidin since there is no specific interaction between BSA and biotin. The 1 micro molar monomeric streptavidin solution was meant to simulate the effects of a high affinity off-target protein population on streptavidin induced biotin-PEG₄-MNP aggregation. The 1 micro molar BSA solution was meant to simulate the effects of a low affinity off-target protein population on streptavidin induced biotin-PEG₄-MNP aggregation. The high affinity off-target protein (monomeric streptavidin) population decreased biotin-PEG₄-MNP streptavidin sensitivity. While the low affinity off-target protein (BSA) population increased biotin-PEG₄-MNP streptavidin sensitivity.