Protein arrangement on modified diamond-like carbon surfaces - An ARXPS study

TL;DR

This study investigates how surface modifications of diamond-like carbon affect protein arrangement at the interface, revealing segregation patterns driven by polar interactions using angle-resolved XPS analysis.

Contribution

It provides new insights into protein-surface interactions on modified DLC surfaces, highlighting the role of surface energy in protein segregation.

Findings

Polar groups are attracted to the surface due to polar interactions.

Segregation of polar and dispersive groups depends on surface energy.

Higher polar surface energy increases segregation of polar groups.

Abstract

Understanding the nature of the interface between a biomaterial implant and the biological fluid is an essential step towards creating improved implant materials. This study examined a diamond-like carbon coating biomaterial, the surface energy of which was modified by Ar+ ion sputtering and laser graphitisation. The arrangement of proteins was analysed by angle resolved X-ray photoelectron spectroscopy, and the effects of the polar component of surface energy on this arrangement were observed. It was seen that polar groups (such as CN, CO) are more attracted to the coating surface due to the stronger polar interactions. This results in a segregation of these groups to the DLC-protein interface; at increasing takeoff angle (further from to DLC-protein interface) fewer of these polar groups are seen. Correspondingly, groups that interact mainly by dispersive forces (CC, CH) were found to increase in intensity as takeoff angle increased, indicating they are segregated away from the DLC-protein interface. The magnitude of the segregation was seen to increase with increasing polar surface energy, this was attributed to an increased net attraction between the solid surface and polar groups at higher polar surface energy.