Development and Evaluation of Anti-Bacterial Surfaces and Coatings for Medical Devices and Implants

Medical devices and implants such as fracture fixators, urinary catheters, prosthetic heart valves and prosthetic joints are intensively used in hospitals nowadays. However, medical devices and implants suffer from biofilm problem, which may result in serious complications and expensive care burden. According to the National Institutes of Health (NIH) report, biofilms are responsible for 65% of microbial infections and 80% of chronic infections (Jamal M 2018). An effective approach to inhibit biofilm formation and decrease infection rate is to change the surface properties of the devices. Applying antibacterial coatings on existing medical devices and implants is widely studied in recent years. So far modified diamond-like carbon (DLC) coatings are one of the most promising candidates. Also, fabricating well-defined nano/microstructured surfaces to prevent bacterial adhesion has been topical. Laser-induced periodic surface structure (LIPSS) has attracted great attention due to effective bacteria-repelling property of the special hierarchical structure. In this study, B, F, Si and Ti doped DLC coatings with various contents were produced by Tecvac Ltd, UK using their magnetron sputtering system. LIPSS surfaces with various dimensions were also produced with picosecond lasers. The surface properties of the coatings and the micro-nano-structured surfaces were characterised using surface analysis facilities, including SEM, EDX and OCA-20. The antibacterial property of modified DLC coatings and LIPSS surfaces were evaluated with typical microorganisms that frequently cause medical devices or implants related infections. The new F, B and Ti doped DLC coatings showed distinct antibacterial efficiency against both Gram-negative and Gram-positive bacteria. Although tested Si-DLC coatings did not show antibacterial property with respect to E.coli and S.aureus in adhesion tests, high removal rates were obtained in removal process. In removal tests, Si-DLC coatings with 12.76 wt.% Si content were able to reduce E.coli attachment by 93.67% at 1h contact time and 87.44% at 5h contact time , comparing to S.S control. Si doped DLC coatings with better performance might be derived by tuning Si content in modified DLC coatings. The bacterial adhesion mechanism of the modified DLC coatings was explained with extended DLVO theory. The experimental results showed that LIPSS structures were very effective on inhibiting bacterial adhesion in the early stage. Lasered surface with 1μm hatch distance reduced E.coli adhesion by 84.61% at 1h contact time, comparing with S.S control. In general, LIPSS surfaces worked better on Gram-negative strains than Gram-positive bacteria. Hatch distance was found to dramatically affect antibacterial ability of LIPSS surfaces while scanning repetition of laser treatment did not show influence on antibacterial efficiency. The change of liquid medium and bacteria concentration would not affect the tendency of antibacterial properties of LIPSS surfaces against hatch distances.