AbstractTitanium dental and orthopaedic implants are an essential component of modern healthcare with their use increasing rapidly over the last few decades. Bacterial infection is one of the most common causes of premature implant failure, and the subsequent revision surgery has serious ramifications for the patient, places financial burdens on healthcare systems and, with rising bacterial resistance, the infections are becoming more difficult to treat.
The aim of this project was to grow antibacterial nanotopographies on titanium and to then further enhance their properties by interfacial functionalisation with an antimicrobial peptide. A range of nanotopographies were formed on titanium using the alkaline hydrothermal method, and their physical properties characterised using a range of analytical techniques, including SEM, AFM, CLSM and OP. After 2-hours growth, distinct nanospikes had formed. These increased in height over time, eventually bending and intertwining to form a ‘pocket’ nanotopography after 4 hours. The crystal structures of the nanotopographies were confirmed to be titanium dioxide using XRD, EDX and XPS.
There is no single optimal quantitative viability technique for assessing nanotopographic surfaces. Consequently, a combination of viability assays and high-resolution imaging were employed. It was found that some of the nanotopographies exhibited anti-biofouling properties and impaired the growth of both Gram-negative and Gram-positive bacteria. Nanotopographies caused indentations in the bacterial cell membrane at points of contact, but there was limited evidence of puncturing of the bacterial cell envelope.
Synthetic antimicrobial peptide, ChoM, was functionalised onto flat and 2-hour nanospike surfaces by physical adsorption and could be released into the local environment in a dose-dependent manner to inhibit bacterial growth. Nanotopography was found to affect the peptide release kinetics relative to flat titanium, due, in part, to differences in hydrophilicity. Alongside effects on bacteria, stem cell studies showed nanotopography to be highly biocompatible which was unaffected by the functionalisation of ChoM.
This research highlights the potential to generate a synergistic antibacterial titanium surface comprising both physical and chemical mechanisms of action. Such an approach could be exploited to develop a next-generation implant surface to combat implant infections, and thus maximise the longevity of medical implants and improve the wellbeing of millions of patients worldwide.
|Date of Award
|24 Mar 2020
|Bo Su (Supervisor), Jim Middleton (Supervisor), Wuge H Briscoe (Supervisor) & Angela H Nobbs (Supervisor)