Zwitterionic Surface Modification via Plasma Immersion Ion Implantation to Improve the Safety and Longevity of Blood-Contacting Medical Devices

Abstract

Blood-contacting medical devices are central in the treatment of many diseases but remain limited by inadequate material biocompatibilities, driving responses such as thrombosis or inflammation that commonly catalyse device dysfunction and threaten patient safety. A promising solution involves modifying the surface chemistry with biocompatible moieties, enabling both mechanical and biological competence. Zwitterionic molecules are an outstanding candidate for surface modification due to their superhydrophilicity that thermodynamically disfavours protein adsorption. Employing plasma immersion ion implantation (PIII) to facilitate grafting may offer an effective, versatile, and scalable platform. Thus, this thesis explores the use of PIII as a linker-free method for the surface modification of medically useful polymers with zwitterionic grafts to create blood-compatible materials.

A model zwitterion (sulfobetaine, SB) was grafted to a model hydrophobic polymer (polyurethane) via PIII treatment, generating a near-superhydrophilic interface (12.98° ± 1.43°) with zwitterionic chemistries (indicated by the presence of -SO3- and -N+), without compromising the bulk tensile or flexural mechanical properties. Grafting was also effective on a range of other organic materials. Optimisation studies were performed to augment graft stability, such as integrating a crosslinker to achieve low molecular mobility. This protocol was demonstrated to limit various adverse biological responses, such reducing fibrinogen adsorption by 88%, thrombosis by up to 80%, TNF- expression by 17%, M1 macrophage differentiation by 50%, and calcification by 83%. Finally, the protocol was applied to tubular and valvular geometries, with the latter demonstrating effective treatment without affecting hydrodynamic performance.

Collectively, this thesis presents a promising advance towards creating increasingly blood-compatible medical devices, facilitating progress towards safer and more durable devices.