Adsorption isotherms constructed from time-and-concentration-dependent advancing contact angles θ, show that the profound biochemical diversity among ten different blood proteins with molecular weight spanning 10-1000 kDa has little discernible effect on the amount adsorbed from aqueous phosphate-buffered saline (PBS) solution after 1 h contact with a particular test surface selected from the full range of observable water wettability (as quantified by PBS adhesion tension τa = γ1v cos θa where γ1v is the liquid-vapor interfacial tension and θa is the advancing PBS contact angle). The maximum advancing spreading pressure, Πamax, determined from adsorption isotherms decreases systematically with τa for methyl-terminated self-assembled monolayers (CH3 SAM, τ° = -15 mN/m), polystyrene spun-coated onto electronic-grade SiOx wafers (PS, τ = 7.2 mN/m), aminopropyltriethoxysilane-treated SiOx surfaces (APTES, τ - 42 mN/m), and fully water wettable SiOx (τ = 72 mN/m). Likewise, the apparent Gibbs' surface excess [Γsl - ΓsV], which measures the difference in the amount of protein adsorbed Γ (mol/cm2) at solid-vapor (SV) and solid-liquid (SL) interfaces, decreases with tau; from maximal values measured on the CH3 SAM surface through zero (no protein adsorption in excess of bulk solution concentration) near τ = 30 mN/m (θa, = 65°). These latter results corroborate the conclusion drawn from independent studies that water is too strongly bound to surfaces with τ > 30 mN/m to be displaced by adsorbing protein and that, as a consequence, protein does not accumulate within the interfacial region of such surfaces at concentrations exceeding that of bulk solution (Γ[ sl - Γsv] = 0 at τ = 30 mN/m). Results are collectively interpreted to mean that water controls protein adsorption to surfaces and that the mechanism of protein adsorption can be understood from this perspective for a diverse set of proteins with very different amino acid compositions.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Surfaces and Interfaces