http://hdl.handle.net/11375/26229

Chau, Colleen (2021) Antifouling Surface Modifications for Multiple Materials, MacSphere Open Access Dissertations and Theses, http://hdl.handle.net/11375/26229

Biomaterials used in biomedical implants, diagnostic devices, and in-situ sensors, all face the issue of biofouling. Surface modification of biomaterial surfaces with antifouling polymers can prevent non-specific adsorption of proteins and other bio-foulants onto these surfaces. Although there are many antifouling polymers to chose from, getting the polymers onto different materials is challenging as the surface modification process is dependent on the substrate’s surface chemistry. This limits the kinds of materials that are able to be modified, especially in devices made with several materials that must be modified as a single unit. Therefore, the goal of this research is to develop an effective antifouling surface modification that is compatible with different types and classes of biomaterials. A three-step modification approach was taken to form dense antifouling polymer brushes. The surfaces were first activated using oxygen plasma to increase the density of surface hydroxyl groups. Next, a silane coupling agent with an Atom Transfer Radical Polymerization (ATRP) initiator was attached to the activated surfaces. Finally, an antifouling zwitterionic monomer was polymerized on the surface using an aqueous controlled living radical polymerization technique, Surface Initiated - Activators Regenerated by Electron Transfer – Atom Transfer Radical Polymerization (SI-ARGET-ATRP). Two zwitterionic antifouling polymers, poly(carboxybetaine methacrylate) (pCBMA), and poly(sulfobetaine methacrylate) (pSBMA) were investigated. Clinically- and environmentally-relevant materials were studied and include poly(dimethylsiloxane) (PDMS), poly(ether ether ketone) (PEEK), titanium, silicon, and 3D printed stainless steel. Water contact angle (WCA) analysis showed that surfaces modified with zwitterionic polymers became more hydrophilic. WCA analysis may not be suitable for evaluating non-modified 3D printed surfaces due to their poor surface finish, and this material requires further surface topography characterization. Atomic force microscopy (AFM) and ellipsometry showed that the zwitterionic polymer layers did not necessarily have to be thick to produce their hydrophilic effect. AFM also revealed that each step of the surface modification process produced different roughness effects on all of the different surfaces. The zwitterionic layer with the smoother surface tended to better resist bovine serum albumin (BSA) adsorption. Radiolabelled BSA experiments showed reduced fouling on all 2D samples but to different degrees. The pCBMA modification was not successful in preventing BSA fouling on 3D printed 316L stainless steel. Full or partial BSA fouling may be due to the hydrolytic instability of the silane coupling agent, used to form covalent bonds between the antifouling polymers and the different surfaces, although further investigation is required to validate this hypothesis. Improving the long-term stability of silanes or research with other multi-surface compatible coupling agents that have better long-term stability in aqueous solutions should be pursued.

https://macsphere.mcmaster.ca/bitstream/11375/26229/2/Chau_Colleen_finalsubmission202102_MASc.pdf