Biofilm-Targeting Superhydrophobic Coating Reduces Microbial Accumulation on Titanium Surface

Objectives: Preventing implant-biofilm-related infections remains a challenge for the success of dental implants rehabilitation. Superhydrophobic surfaces are promising approaches to reduce microbial accumulation by its non-fouling property. However, studies are limited to two-step techniques and did not consider the polymicrobial characteristic of implant-biofilm-related infections. This study developed a one-step technique using glow discharge plasma (GDP) to create a biocompatible superhydrophobic coating on titanium surface to reduce polymicrobial biofilms formation.
Methods: Superhydrophobic coating was developed on titanium discs by GDP using argon, oxygen and hexamethyldisiloxane. Untreated titanium discs were used as control. Wettability, morphology, roughness, film thickness, chemical composition, electrochemical behavior, biocompatibility (fibroblast cells) and proteomic profile of salivary proteins adsorbed on the surfaces were evaluated. Non-fouling property of superhydrophobic surface was tested in vitro and in situ. Microcosm model (saliva as inoculum) at 2 and 24h of biofilm formation, and specific microorganisms (Candida albicans at 2h and Streptococcus mutans at 4h) were used in the in vitro analysis. The number of viable microorganisms was determined. For the in situ analysis, volunteers wore a palatal appliance containing discs (72h) and the profile of 40 bacterial species was analyzed using DNA-DNA checkerboard. To test whether reduced biofilm formation on developed surface could enhance antimicrobials effect, 24h-biofilm was exposed to chlorhexidine.
Results: Plasma coating changed titanium surface morphology, showing superhydrophobic profile (>150^o), and increased roughness and corrosion resistance (p<0.05, t-test), besides slightly altered protein adsorption composition at proteomic level. Superhydrophobic surface showed biocompatibility and significant reduction on all bacterial and fungal adhesion and biofilm formation (p<0.05, t-test) tested, and 1.5-fold reduction of 40 bacterial species formed in situ. Biofilms on superhydrophobic surface showed lower antimicrobial resistance against chlorhexidine (p<0.05, t-test).
Conclusions: The novel superhydrophobic coating developed by GDP is a promising biocompatible strategy to reduce microbial adhesion and biofilm formation on dental implant surface.