Geraniol in vitro and geraniol-based emulsion ex vivo potential against four-species Streptococcus spp. biofilm relevant for dentistry

Abstract

Objective: Concerning the importance of developing novel oral hygiene adjuncts, the aim of this study was to screen antibacterial/antibiofilm potential of geraniol and to formulate its stable nanoemulsion(s), capable to combat caries-related streptococcal multispecies biofilm. Materials and methods: Antibacterial and antibiofilm activities of geraniol were estimated in microdilution and crystal-violet assays, respectively. Five geraniol-based emulsions with Tween80 were formulated and screened for particle size diameter and stability, using dynamic light scattering measurements. The selected emulsion was characterized by TEM, and ex vivo screened against four-species biofilm settled on enamel discs, by determination of CFU. Results: The antibacterial potential of geraniol was moderate (MICs 0.55–1.11 mg/mL against S. mutans, S. sanguinis, S. gordonii and S. mutans). Geraniol significantly prevented biofilm formation and disrupted pre-formed ones (inhibition ranges against all isolates were 12.00–93.66 %, and 55.54–100 %, respectively). Emulsions (Eger:tween80) E200:200, E500:500, and E800:800 were stable and nanosized (Zavg˂200 nm). TEM of E800:800 revealed black spherical spots surrounded by grey stain. Ex vivo four-species streptococcal biofilm disruption assay showed notable inhibitory potential of E800:800 (ΔLogCFU 1.77 and 3.89, solely and in combination with chlorhexidine, respectively). Conclusion: E800:800 showed ex vivo potential against streptococcal multispecies biofilm, especially in combination with chlorhexidine. Clinical Significance: Presented results encourage further research of the examined nanoemulsions as potential part of daily oral hygiene, aiming to provide prevention of caries development.