Protein Adsorption at Nanorough Titanium Oxide Surfaces: The Importance of Surface Statistical Parameters beyond Surface Roughness

Qing Yun,Qin Qin,Yu Yang,Guido Grundmeier,Adrian Keller,Steffen Knust,Sabrina Schwiderek

doi:10.3390/nano11020357

Abstract

The nanoscale surface topography of biomaterials can have strong effects on protein adsorption. While there are numerous surface statistical parameters for the characterization of nanorough surfaces, none of them alone provides a complete description of surface morphology. Herein, a selection of nanorough titanium oxide surfaces has been fabricated with root-mean-square roughness (Sq) values below 2.7 nm but very different surface morphologies. The adsorption of the proteins myoglobin (MGB), bovine serum albumin (BSA), and thyroglobulin (TGL) at these surfaces was investigated in situ by ellipsometry to assess the importance of six of the most common surface statistical parameters. For BSA adsorption, both protein film thickness and time constant of adsorption were found to scale linearly with Sq s. For TGL, however, the same adsorption characteristics depend linearly on the surface skewness (Ssk), which we attribute to the rather extreme size of this protein. Finally, a mixed behavior is observed for MGB adsorption, showing different linear correlations with Sq and Ssk. These results demonstrate the importance of a thorough morphological characterization of the surfaces employed in protein adsorption and possibly also cell adhesion studies.

Highlights

Received: 21 December 2020The adsorption of proteins from biological fluids represents the initial step in the response of biological systems to artificial materials [1,2,3,4]
We have investigated the adsorption of the three globular proteins MGL, bovine serum albumin (BSA), and TGL at a selection of titanium oxide surfaces with almost identical chemical compositions but very different surface topographies
By thoroughly characterizing the morphologies of these surfaces by atomic force microscopy (AFM), we were able to screen for possible correlations between a selection of the most widely employed surface statistical parameters and the time constants of adsorption as well as the thickness of the irreversibly adsorbed protein films

Summary

Introduction

Received: 21 December 2020The adsorption of proteins from biological fluids represents the initial step in the response of biological systems to artificial materials [1,2,3,4]. Over the last few decades, a tremendous amount of research has focused on establishing correlations between the physicochemical surface properties and the structural, functional, and biological properties of the adsorbed proteins [5,6,7,8] While these attempts turned out rather successful with regard to the effects of surface chemistry and wettability [1,8,9,10], the role of surface topography is still not understood in detail. In the context of the random sequential adsorption (RSA) model, it was recently shown that nanoscale surface topography can result in significantly increased protein adsorption [13] In this particular model, steric hindrance between adsorbing proteins prevents the complete coverage of the surface. Can result in reduced steric hindrance and an increase in surface coverage, while the opposite may Accepted: 26 January 2021

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Results

Conclusion