Streptavidin-Response Curves for Pristine Biotinylated Magnetic Nanoparticles and for Biotinylated Magnetic Nanoparticles Encased in a Monomeric Streptavidin Corona

Biotin-PEG₄-MNPs underwent an approximate 12-hour room temperature incubation in a 1 micro molar monomeric streptavidin solution (3 monomeric streptavidins per MNP). Then, the biotin-PEG₄-MNPs were exposed to a streptavidin serial dilution spanning from 0 to 144.97 nM streptavidin in 1x PBS . The bound monomeric streptavidin was meant to simulate a protein corona that masked a portion of available biotin for streptavidin binding on the MNP surface. A decreased biotin density due to a monomeric streptavidin corona masking a portion of the available biotin for streptavidin binding decreased the streptavidin-response curve 𝛥𝜙₃ and shifted the streptavidin concentration at which the maximum 𝜙₃ occurred to a higher concentration of streptavidin. Wherein, 𝛥𝜙₃ describes the change in 𝜙₃ between MNPs in solutions void of target and MNPs at the peak of target induced aggregation.