Abstract
Background: Dental plaque is a highly resilient biofilm whose early establishment and long-term regrowth limit the durability of conventional chemical plaque control. Biodegradable nanoparticles may offer a preventive advantage by improving surface retention and enabling controlled release of antibiofilm agents at the enamel–pellicle interface.
Objective: To evaluate the effectiveness of biodegradable nanoparticle formulations in preventing dental plaque formation and to assess persistence of antibiofilm activity under repeated microbial challenge in an in-vitro model conducted in a tertiary hospital laboratory setting in Islamabad, Pakistan.
Methods: An in-vitro experimental study was performed using saliva-conditioned human enamel blocks. Two biodegradable nanoparticle systems were prepared and characterized: chitosan nanoparticles (CS-NPs) and poly(lactic-co-glycolic acid) nanoparticles (PLGA-NPs), each tested as blank (no active) and active formulations. Chlorhexidine 0.12% (CHX) served as a positive control and untreated enamel as a negative control. Biofilm formation (primarily Streptococcus mutans) was assessed at 6, 24, 48, and 72 hours using (i) crystal violet biomass (OD570), (ii) viable counts (log10 CFU/mL), and (iii) resazurin metabolic activity (% of untreated). Long-term effectiveness was evaluated in a repeated-challenge model for 14 days. Release kinetics were measured in artificial saliva, and screening biocompatibility was assessed using oral cells (24-hour viability). Experiments were performed in triplicate across three independent runs (n = 9 per group/time point).
Results: Active nanoparticles demonstrated consistent inhibition of early plaque development across all endpoints, while blank nanoparticles were close to untreated controls. At 24 hours, biofilm biomass was reduced from 1.33 ± 0.06 (untreated) to 0.64 ± 0.06 (active CS-NPs) and 0.66 ± 0.06 (active PLGA-NPs), compared with 0.76 ± 0.08 (CHX). Similar trends were observed for viable counts and metabolic activity through 72 hours; at 72 hours, viable load was 8.34 ± 0.11 log10 CFU/mL (untreated) versus 7.07 ± 0.09 (active CS-NPs), 7.08 ± 0.10 (active PLGA-NPs), and 7.35 ± 0.10 (CHX). In the repeated-challenge model, sustained suppression was most evident at Day 14: biomass was 2.03 ± 0.07 (untreated), 1.48 ± 0.09 (CHX), 1.03 ± 0.06 (active CS-NPs), and 1.12 ± 0.09 (active PLGA-NPs). Release testing showed a faster early release profile for active CS-NPs and a more gradual release for active PLGA-NPs, supporting extended activity. Cell viability remained comparatively high for nanoparticle groups across the tested concentration range, while CHX showed a steeper concentration-dependent reduction.
Conclusion: Biodegradable nanoparticles, when formulated as active delivery systems, significantly inhibited early plaque biofilm formation and maintained stronger antibiofilm effects than chlorhexidine under repeated microbial challenge. These findings support biodegradable nanoparticle platforms as promising preventive candidates for sustained plaque control, warranting validation in multispecies flow models and clinical translation studies in high-burden settings.