A Nanoparticle-Based Biofilm Inhibitor for Pediatric Caries Prevention

Hypothesis and Objective: The purpose was to determine whether cerium oxide nanoparticles (CeO2-NP, 3-4 nm) in solution were effective in inhibiting the formation of a sucrose-dependent biofilm of Streptococcus mutans on hydroxyapatite (HA) discs in the presence of saliva. Methods: A CeO2-NP (5 mM (Ce)) stock solution prepared from Ce(IV) salt hydrolysis was prepared and stored at 22 degrees Celsius before use. Minimal inhibitory concentration (MIC) and minimal biofilm inhibitory concentration (MBIC) against S. mutans were determined using chemically defined medium (CDM) anaerobically for 24 hours (MIC) or 48 hours (MBIC). Pooled saliva was collected from six pediatric patients aged six to seven by chewing gum base. S. mutans was then grown anaerobically for 48 hours on saliva coated HA discs in the presence of 400uM CeO2-NP and compared against controls. Planktonic bacteria were discarded, while the adherent biofilm was ultrasonically removed and treated with a five-fold serial dilution before regrowth on agar plates. Colony-forming units were then recorded. Data was analyzed using an independent-samples t-test. Results: MIC was determined to be 250uM and MBIC was 1mM against S. mutans. Compared to the control, HA discs coated with human saliva in the presence of 400uM CeO2-NP have demonstrated a 95% biofilm inhibition (P<.01). Visual observation of bacteria in the intervention group post anaerobic growth showed a loose, amorphous character compared to the tightly adherent biofilm in the control. Conclusions: Preliminary results demonstrate that CeO2-NP prepared from Ce(IV) salt hydrolysis at 400M disrupt the growth of S. mutans biofilm on hydroxyapatite models. IRB/ACC protocol: 2018-1075.