Development and Evaluation of Advanced Anti-Bacterial Surfaces and Coatings for Preventing Medical Devices-Associated Infections

Abstract

Medical device-associated infections (MDAIs) have become a critical concern in modern healthcare. Devices such as catheters, implants, and surgical instruments provide surfaces for bacterial colonization upon contact with human tissues. As bacterial colonies aggregate, they form resilient biofilms that exhibit high persistence and resistance to removal. These biofilms not only compromise device functionality but also increase surgical risks, prolong hospitalization, and escalate healthcare costs. Moreover, biofilms evade host immune responses, potentially leading to localized or systemic infections with life-threatening consequences. Conventional antibiotic therapies have proven largely ineffective against biofilms and may exacerbate antimicrobial resistance. Consequently, there is an urgent need to develop antibacterial surfaces for medical devices to prevent and control such infections. Recent strategies focus on antimicrobial materials, surface coatings, and advanced disinfection methods to minimize bacterial adhesion and transmission.

In this PhD research, laser-induced periodic surface structures (LIPSS) were first fabricated on titanium (Ti) to enhance bacterial anti-adhesion. A hybrid approach combining LIPSS with a polydopamine-chitosan-silver nanoparticle (PCA) composite coating demonstrated synergistic mechano-chemical bactericidal effects, achieving 96.9% and 91.9% efficiency against E. coli (Gram-negative) and S. aureus (Grampositive), respectively. Surface characterization via SEM, AFM, EDX, and contact angle measurements (OCA-20) confirmed modifications in morphology, chemistry, and wettability. This dual-functional surface exhibited superior antibacterial and antibiofilm performance compared to individual LIPSS or PCA modifications.

The incorporation of non-metallic elements into diamond-like carbon (DLC) coatings was explored as an alternative strategy to reduce bacterial adhesion and enhance corrosion resistance. Fluorine doped DLC (F-DLC) films with varying fluorine concentrations (0.6–8.0 wt.%) were deposited on 316L SS via PECVD plus magnetron VIII sputtering. Results indicated that higher fluorine content correlated with lower surface free energy and significantly reduced bacterial adhesion. Raman spectroscopy revealed that the sp2/sp3 carbon ratio critically influenced bacterial retention. XDLVO theory was employed to model bacterium substrate interactions, while electrochemical tests in simulated body fluid (37°C) demonstrated that fluoridation reduced corrosion current density and improved protection efficiency to 98% compared to uncoated 316L SS.

Picosecond laser irradiation was utilized to generate tuneable LIPSS by varying parameters (wavelength, scanning speed). Antibacterial efficacy was found to depend on LIPSS periodicity (Λ) and depth (D), with strain-specific responses observed. The Surface Element Integral (SEI) method, combined with XDLVO theory, modelled interactions between S. aureus and LIPSS topographies, yielding predictions consistent with experimental data. Notably, while L- 𝜆 106 (largest Λ/D) showed limited antibacterial activity, it conferred exceptional corrosion resistance, highlighting the versatility of laser processing for tailoring surface properties. This eco-friendly, scalable technique holds promise for medical device applications.

Date of Award	2025
Original language	English
Awarding Institution	University of Dundee
Supervisor	Qi Zhao (Supervisor) & Svetlana A. Zolotovskaya (Supervisor)