Robust Solid Hydrogel Structures for Biomedical Engineering

Abstract

Implant-associated infections and poor tissue integration are major challenges in biomedical applications, often leading to implant failure and revision surgeries. Surface modification strategies, including physical, chemical, and biological methods, have been developed to improve tissue integration and reduce bacterial colonisation. Hydrogel coatings are especially promising due to their biocompatibility, ability to retain bioactive molecules, and capacity to mimic native tissue and extracellular matrix. However, physical attachment methods lack durability, while covalent methods, though more stable, often involve complex, material-specific, and cytotoxic wet-chemistry approaches. Additionally, the widespread use of antibiotics in coatings contributes to resistance, necessitating alternative antibacterial strategies.

This thesis presents a multifunctional implant coating that enhances biocompatibility, promotes soft tissue integration on hard implants, and prevents infection without antibiotics. The key innovations include (1) a novel ion-assisted plasma polymerisation (IAPP) technique for covalently attaching hydrogels to solid surfaces, forming hybrid solid–hydrogel structures (HSHs), and (2) the incorporation of antibacterial carbon dots (CDs) into the HSHs to offer antibiotic-free infection control.

The research examines the effects of plasma-induced radical concentration on hydrogel thickness and crosslinking, the mechanical and interfacial stability of the coatings, and the biocompatibility of the platform. The antibacterial activity, release behaviour, and mechanism of CDs+HSHs are also explored. The findings demonstrate that IAPP enables robust, scalable surface modification for improved soft tissue integration and infection resistance, offering a versatile platform for implantable biomedical devices.