Characterisation of polystyrene coatings after plasma immersion ion implantation and adsorption of protein

TL;DR

This study investigates how plasma immersion ion implantation modifies polystyrene coatings, affecting their structure and ability to covalently immobilize proteins, with detailed analysis of density, composition, and protein retention.

Contribution

It provides detailed characterization of polystyrene surface modifications after PIII and demonstrates protein immobilization stability on treated surfaces, advancing surface modification techniques.

Findings

Argon ions create a denser, shallower modified layer than nitrogen ions.

Density and hydrogen gradients within the layers are resolvable by reflectometry.

Proteins covalently immobilized remain after SDS washing, indicating stable attachment.

Abstract

A polystyrene film spun onto polished silicon substrates was implanted with either nitrogen or argon ions using plasma immersion ion implantation (PIII) and subsequently investigated by X-ray and neutron reflectometry, UV-VIS and FTIR ellipsometry, as well as by FTIR and Raman spectroscopy. The depth profile of the densified carbon structures resulting from the ion collision cascades in the polystyrene coating are clearly observed by both X-ray and neutron reflectometry. Argon ions produce a higher density modified layer at a shallower depth than nitrogen ions. The thickness measured for these graded layers agrees with the expected depths of ion implantation as calculated by SRIM. The sensitivity of X-ray and neutron reflectometry allows resolution of density and hydrogen content gradients within the graphitized layers. The treated layers were found to covalently immobilized protein directly from solution. The tropoelastin protein monolayers immobilized on the surface were characterized. Tropoelastin remained on the surface after SDS washing.