Adsorption and function of recombinant factor VIII at solid-water interfaces in the presence of Tween-80

The adsorption, structural alteration and biological activity of a recombinant Factor VIII was investigated in the presence of the surfactant Tween-80, at hydrophilic and hydrophobic solid-water interfaces. Hydrophilic and silanized, hydrophobic silica surfaces were used as substrates for protein and surfactant adsorption, which was monitored in situ, with ellipsometry. At the hydrophobic surface, the presence of Tween in the protein solution resulted in a reduction in amount of protein adsorbed, while rFVIII adsorption at the hydrophilic surface was entirely unaffected by the presence of Tween. These observations were attributed to high binding strength between Tween and the hydrophobic surface, and low binding strength between Tween and the hydrophilic surface. Colloidal particles bearing hydrophilic and hydrophobic surfaces, and net positive or negative surface charge, were used as substrates for rFVIII adsorption in evaluation of tertiary structure change and biological activity retention at interfaces. Fluorescence emission spectroscopy showed that rFVIII tertiary structure was changed upon exposure to hydrophobic nanoparticle surfaces. Similarly, the biological activity of rFVIII (based on the activated partial thromboplastin time) was reduced at hydrophobic surfaces. At high surfactant concentration, these properties were better preserved. This was attributed to Tween adsorption sterically inhibiting rFVIII adsorption. While hydrophilic surfaces were associated with relatively high rFVIII adsorption, they did not induce large changes in structure or activity. This was attributed to the formation of a tightly packed, ordered adsorbed layer on these surfaces, governed by electrostatic attraction and not mediated by the rFVIII active site.