Exploring the interaction of an anionic magnetic surfactant nanoparticles with BSA: From molecular insights to...

This study presents a multiscale investigation on the adsorption of bovine serum albumin (BSA) into anionic magnetic surfactant nanoparticles, offering novel insights into protein-nanostructure interactions. Fe₃O₄ nanoparticles were coated with sodium bis (2-ethylhexyl) sulfosuccinate (AOT) to form anionic magnetic surfactant nanoparticles (AOT-MNPs). The structure and components of synthesized nanoparticles were analyzed using FTIR, XRD, BET, DLS, TEM, and SAXS, and the results confirmed the AOT-MNPs structure with a uniform size (2.52 nm). The study investigated the impact of varying pH levels, ionic strengths, temperatures, and initial concentrations on the adsorption performance of BSA. Notably, we discovered a pH-dependent surfactant release phenomenon during BSA adsorption, which was fully suppressed by an increase in the ionic strength of the solution, offering a new level of tunability in nanomaterial-protein interfaces. The adsorption process was spontaneous and heterogeneous, following the Toth isotherm model, and the peak adsorption of 171.3 mg g^-1 was achieved at pH 3.5, 0.2 M NaCl, and 25 °C with a slight unfolding of BSA's α-helical structure. Electrostatic interactions dominate at low BSA concentrations, while hydrophobic ones prevail at high concentrations, supported by molecular studies, confirming synergistic hydrophobic, electrostatic, hydrogen bonding, and metal interactions.