Construction and Characterization of Polyethylene Glycol/Sodium Alginate Hydrogel Loaded With Zirconia Nanoparticles: Potential Antibacterial and Antibiofilm Agent to Inhibit Dental Caries In Vitro and In Vivo

Biofilm formation on tooth surfaces is a primary contributor to dental caries and periodontal diseases. Streptococcus mutans is recognized for its role in biofilm production, significantly influencing the development of dental caries. Key virulence factors associated with S. mutans biofilms include acid production, acid tolerance, and the synthesis of exopolysaccharides (EPS). This study presents a novel approach by focusing on the loading of biosynthesized zirconia nanoparticles (ZrO2 NPs) onto polyethylene glycol/sodium alginate (PEG/SA) hydrogel nanocomposite, evaluating their effects on the biofilm-forming ability of S. mutans both in vivo and in vitro. ZrO2 NPs were biosynthesized using Citrus aurantifolia (C. aurantifolia) extract and incorporated into the PEG/SA hydrogel beads through a sol-gel process. The formation of ZrO2 NPs and the PEG/SA/ZrO2 NPs hydrogel nanocomposite was confirmed through diverse analyzes, including UV-visible spectroscopy, particle size measurement, morphology examination, spectral analysis, thermal gravimetric analysis (TGA) and hemolysis studies. The average particle size of the ZrO2 NPs was approximately 26 nm, while the PEG/SA/ZrO2 NPs hydrogel beads exhibited a highly porous, sheet-like surface structure. In vitro results demonstrated inhibition zones of 30 and 28 mm for ZrO2 NPs and PEG/SA/ZrO2 NPs hydrogel beads against S. mutans, respectively, with a minimum inhibitory concentration (MIC) of 12.5 mg/mL. The growth curve analysis indicated a complete decline in S. mutans growth with an 87% reduction in biofilm formation when treated with PEG/SA/ZrO2 NPs hydrogel beads. SEM analysis revealed that S. mutans cells appeared lysed or crumpled, losing their characteristic coccal shape after exposure to the hydrogel beads. Additionally, SEM images confirmed the effective prevention of S. mutans attachment to teeth when encapsulated with PEG/SA/ZrO2 NPs hydrogel, altering the morphology of mature biofilms that developed on the teeth after treatment. Finally, the incorporation of biosynthesized ZrO2 NPs into PEG/SA hydrogels demonstrates significant potential as an effective strategy for inhibiting S. mutans biofilm formation and may serve as a promising topical agent for reducing dental caries. Further studies could explore the long-term efficacy and potential clinical applications of this nanocomposite in oral health care.