Preparation, Characterization And Basic Application Of ZnO@CaCO₃-PDMS Composite Material Based On Dental Caries Diagnosis And Treatment

Background and objective:Dental caries is the most common oral disease,which seriously affects oral health,and its incidence rate has been high.Early diagnosis,prevention,and treatment of dental caries are of great clinical significance in maintaining oral health.In this experiment,zinc oxide quantum dots（ZnO QDs）were used as fluorescent probes,and ZnO@CaCO₃ composite nanomaterials were formed by coating CaCO₃ on the surface of ZnO QDs through a diffusion method.In addition,highly transparent polydimethylsiloxane（PDMS）was used as the matrix to prepare ZnO@CaCO₃-PDMS composite materials to achieve rapid diagnosis,precise positioning,and treatment of dental caries sites.Methods:ZnO@CaCO₃ nanocomposites were prepared and characterized by TEM,XRD,XPS,FT-IR,Zeta,and fluorescence spectroscopy to study their structural morphology and chemical composition.ZnO-PDMS and ZnO@CaCO₃-PDMS composite materials with different component concentration ratios were prepared,and their diagnostic performance for bacterial metabolites was evaluated by measuring the changes in their fluorescence intensity over time in solutions with different concentrations of volatile sulfur compounds（H₂S,CH₃SH,and CH₃SCH₃）using a fluorescence spectrophotometer.The biocompatibility of the composite materials was evaluated using the CCK-8 and live/dead cell staining assays.The antibacterial properties of the composite materials against Streptococcus mutans and Escherichia coli were further evaluated using the plate counting method,and their effects on the virulence of S.mutans were assessed using a bacterial acid production experiment.Results:ZnO QDs,ZnO@CaCO₃,ZnO-PDMS and ZnO@CaCO₃-PDMS nano-composites were successfully prepared,with ZnO QDs having an average diameter of about 6 nm.The optimal emission wavelength of ZnO QDs was 534 nm,while that of ZnO@CaCO₃ was 528 nm,exhibiting quantum dot fluorescence properties.The fluorescence of both ZnO-PDMS and ZnO@CaCO₃-PDMS can be quenched by volatile sulfur-containing compounds（VSCs）within a short period of time.These composite materials exhibit high sensitivity for detecting bacterial sulfur-containing metabolites.Cell viability tests showed that the survival rates of normal cells after treatment with the composite materials were all above 75%,indicating low toxicity and good biocompatibility of the composites.Moreover,these composite materials show strong antibacterial activity against Streptococcus mutans and Escherichia coli at the tested concentrations,with inhibition rates of over 99%.ZnO@CaCO₃-PDMS exhibits stronger ability to inhibit acid production in bacterial cultures,leading to an increase in pH of the bacterial culture medium.Conclusion:A novel composite material with visible fluorescence and pH-responsive antibacterial properties was successfully prepared.The composite material exhibits visible fluorescence,and can specifically react with VSCs produced by bacterial metabolism in caries lesions and plaque,leading to fluorescence quenching and diagnostic capabilities.Additionally,in the acidic microenvironment of caries,ZnO@CaCO₃-PDMS can increase the pH of bacterial liquid,inhibit the acid-producing ability of bacteria,and demonstrate excellent antibacterial properties,which is beneficial for the remineralization of caries and can comprehensively achieve early diagnosis and treatment of hidden caries.