Surface Tailoring for Controlled Protein Adsorption:  Effect of Topography at the Nanometer Scale and Chemistry

Abstract

Protein adsorption behavior is at the heart of many of today's research fields including biotechnology and materials science. With understanding of protein-surface interactions, control over the conformation and orientation of immobilized species may ultimately allow tailor-made surfaces to be generated. In this contribution protein-surface interactions have been examined with particular focus on surface curvature with and without surface chemistry effects. Silica spheres with diameters in the range 15-165 nm with both hydrophilic and hydrophobic surface chemistries have been used as model substrates. Two proteins differing in size and shape, bovine serum albumin (BSA) and bovine fibrinogen (Fg), have been used in model studies of protein binding with detailed secondary structure analysis being performed using infrared spectroscopy (IR) on surface-bound proteins. Although trends in binding affinity and saturation values were similar for both proteins, albumin is increasingly less ordered on larger substrates, while fibrinogen, in contrast, loses secondary structure to a greater extent when adsorbing onto particles with high surface curvature. These effects are compounded by surface chemistry, with both proteins becoming more denatured on hydrophobic surfaces. Both surface chemistry and topography play key roles in determining the structure of the bound proteins. A model of the binding characteristics of these two proteins onto surfaces having differing curvature and chemistry is presented. We propose that properties of an adsorbed protein layer may be guided through careful consideration of surface structure, allowing the fabrication of materials/surface coatings with tailored bioactivity.

Protein Adsorption on Nano-scaled, Rippled TiO2 and Si Surfaces

“…By doing this, the contact area between substrate and protein is increased assuring adsorption. This theory accords well with the findings by Rasmusson et al [21] and Roach et al [30] for the adsorption of HPF on polymer nanostructures and silica nanospheres, for example. The dependence of the orientation of the proteins on the ripple wavelength can be explained as follows.…”

Nano-scale superhydrophobicity: suppression of protein adsorption and promotion of flow-induced detachment

“…The large loss of adsorbed material from the rough surfaces supports our view that the pores were not penetrated by the protein solution as internal protein would not be removed very easily by flow. Reduced binding strength has previously been reported for BSA on high curvature surfaces 24 .…”

“…It has previously been reported that proteins and peptides are affected by nano-structures of similar size to those used here 24,32,33 .…”

“…On nano-scale roughness the curvature of the surface approaches protein molecular dimensions, reducing the contact area unless the protein molecules deform. 23,24 The smallest scale roughness used here is similar to the dimensions of the protein used so this effect may play a role. It is important to note that, although the materials are porous, only the surface of the material is exposed to solution as water cannot enter the hydrophobic pores at the pressures used.…”

Bridging interactions of proteins with silica nanoparticles: The influence of pH, ionic strength and protein concentration

“…13 Protein adsorption on nanoparticles can be affected by the high surface curvature of the particles. [14][15][16][17] Much attention was paid to the question to what extent the structure of proteins is perturbed by adsorption onto hydrophilic or hydrophobic nanoparticles, [17][18][19] or if the interaction with their strongly curved surface can promote aggregation and brillation of proteins. 20,21 On the other hand, it is also possible that the adsorption of the protein causes bridging of two or more nanoparticles.…”