IADR Abstract Archives
Novel Biofilm Inhibitors of Oral Streptococci
Objectives: The etiology of dental caries is attributed to tooth-borne biofilms comprising Streptococci. Current preventive treatments employ topical bactericidal agents not suited for long-term use due to their propensity to affect healthy flora. Non-bactericidal biofilm inhibitors could potentially limit plaque formation without undesirable side effects. The objective is to test the efficacy of cerium oxide nanoparticles (CeO2-NP, hydrodynamic radius = 4 nm) as non-bactericidal biofilm inhibitors of oral Streptococci. Static in vitro biofilm inhibition assays were utilized to quantify average percent biofilm inhibition by CeO2-NP against S. mutans (UA159) and S. sobrinus (6715).
Methods: The cells were grown in the presence of 1% sucrose and a known antimicrobial agent (including CeO2-NP) on a microtiter plate. After 24 hrs, the cells were removed, the wells were washed and the residual film was stained with crystal violet dye. The adherent, dyed biofilm material was re-dissolved in 30% acetic acid and quantified by UV-Vis Spectroscopy. The measurements were carried out in triplicate and the average percent inhibition was calculated against the positive control. A bacterial growth curve was used to evaluate the effects of CeO2-NP on S. mutans growth.
Results: CeO2-NP was tested against several known antimicrobial metal-containing agents: cerium nitrate, zinc sulfate and ferric chloride for their efficacy as biofilm inhibitors. At 200 µM (metal) concentration, CeO2-NP effectively inhibited biofilm formation in S. mutans by an average of 42%, and S. sobrinus by 28%, over 24 hrs growth. The inhibition by CeO2-NP was significantly higher than all other salts tested, by a minimum of 25%. Bacterial growth curve studies of S. mutans in the presence of 200 µM CeO2-NP showed minimal effect on the growth rate, suggesting a non-bactericidal mechanism of biofilm inhibition.
Conclusions: CeO2-NP are effective as non-bactericidal biofilm inhibitors of oral Streptococci in vitro. This research has several applications in oral medicine.
Methods: The cells were grown in the presence of 1% sucrose and a known antimicrobial agent (including CeO2-NP) on a microtiter plate. After 24 hrs, the cells were removed, the wells were washed and the residual film was stained with crystal violet dye. The adherent, dyed biofilm material was re-dissolved in 30% acetic acid and quantified by UV-Vis Spectroscopy. The measurements were carried out in triplicate and the average percent inhibition was calculated against the positive control. A bacterial growth curve was used to evaluate the effects of CeO2-NP on S. mutans growth.
Results: CeO2-NP was tested against several known antimicrobial metal-containing agents: cerium nitrate, zinc sulfate and ferric chloride for their efficacy as biofilm inhibitors. At 200 µM (metal) concentration, CeO2-NP effectively inhibited biofilm formation in S. mutans by an average of 42%, and S. sobrinus by 28%, over 24 hrs growth. The inhibition by CeO2-NP was significantly higher than all other salts tested, by a minimum of 25%. Bacterial growth curve studies of S. mutans in the presence of 200 µM CeO2-NP showed minimal effect on the growth rate, suggesting a non-bactericidal mechanism of biofilm inhibition.
Conclusions: CeO2-NP are effective as non-bactericidal biofilm inhibitors of oral Streptococci in vitro. This research has several applications in oral medicine.