QCM analysis of chlorhexidine interaction with salivary and S. gordonii films on titanium implant surfaces

Abstract

Background In implant surgery, preoperative and postoperative mouth rinsing with Chlorhexidine (CHX) has been regularly applied for the prophylaxis of peri-implantitis. Studies indicate that titanium (Ti) implant materials might be involved in both uptake and release of CHX, suggesting antiplaque activity through prolonged CHX release. However, during the primary bacterial colonization period, the interactions between bacteria, salivary pellicle films and CHX on Ti surfaces are still unclear in detail. Aim/Hypothesis This study aimed at using a mass-sensitive on-line sensor system to analyze surface interactions of CHX on the adsorption processes of the early oral colonizer S. gordonii (Sg), and the antibacterial efficiency of CHX on planktonic and pre-adsorbed Sg on Ti conditioned with or without saliva. Material and Methods A conventional mass-sensitive quartz crystal microbalance (QCM) device with frequency (f) and dissipation (D) output (qCell T+ 3T Analytik, Germany) and Ti-coated smooth quartz crystal sensors were used in a flow-system for real-time monitoring of dynamic macromolecule surface, bacteria surface, and macromolecule bacteria interactions. Sg was precultured in Schaedler medium overnight and diluted to OD620 = 0.54. CHX mouth rinsing (0.12%) was used. Human saliva (Sal) was collected once from one healthy volunteer for the complete study and sterile-filtered by low protein binding syringe filters. The QCM flow sequences of different groups were- A) CHX-Sg+ B) Sal-CHX-Sg+ C) Sg-CHX+ D) Sal-Sg-CHX+ E) mixed CHX+Sg+ F) Sal-mixed CHX+Sg. Sg was run for 2 hours and CHX, Sal, PBS for 30 minutes, respectively. PBS flow was used as baseline and for washing. After QCM runs, the vitality of Sg on Ti sensor surfaces was analyzed by Live Dead staining and fluorescence microscopy. Results (A) The interaction of CHX on Ti is a “U”-shaped signal indicating reversible interaction- fast f decrease of 361 Hz, fast increase of 332 Hz and final residue of 128 ng/cm2. Subsequent staining revealed a dense, vital (green) bacterial film. (B) CHX interaction with saliva-coated Ti induced a reversible f decrease of 302 Hz and an increase of 338 Hz upon PBS rinsing. Subsequent Sg run results in a dense vital film. (C) On pre-adsorbed Sg films, CHX induced a large f decrease of 985 Hz, which represents a strong CHX adsorption interaction, followed by an increase of 818 Hz caused by desorption upon PBS, ending with a 740 ng/cm2 residue and dense red stained films. (D) On surfaces preconditioned with saliva and Sg, CHX caused a 753 Hz decrease, followed by a reversible 586 Hz increase upon PBS ending with a CHX residue of 737 ng/cm2 and killed bacteria. (E, F) A mix of CHX and planktonic Sg on Ti with or without saliva led to very small f changes and dead bacteria with comparable low film density. Conclusions and Clinical Implications CHX bind rapidly but almost reversibly to Ti, and the small residues cannot kill colonizing Sg. CHX bind similarly fast but stronger to Sg films. Higher amounts of residual CHX were found on Sg films than on pure Ti. This QCM study shows that free CHX inhibits planktonic bacterial binding with bactericidal effect, but cannot remove significant amounts of biofilm on Ti implant abutment surfaces. These online results coincide with earlier findings from conventional, static incubation experiments.