Synergistic Effects Of Graphene Quantum Dots And Carbodiimide In Promoting Resin-Dentin Bond Stability

Objectives:Resin-based dental adhesion is mostly utilized in minimally invasive operative dentistry.However,improving the durability and stability of resin–dentin bond interfaces remain a challenge.Graphene quantum dots（GQDs）reinforced by 1-ethyl-3-（3-dimethylaminopropyl）carbodiimide（EDC）were introduced to modify the resin–dentin bond interfaces,thereby promoting their durability and stability.Methods:GQDs,EDC,and EDC+GQDs groups were designed to evaluate the effects of GQDs and EDC on collagenase activity,the interaction of GQDs with collagen,and the resin–dentin interface.The cross-linking mechanism between graphene quantum dots and collagenFirst of all,Ninhydrin assay was used to evaluate the cross-linking degree of every group.the 5 samples in each group（n=5）,SDS-PAGE was used to evaluate the cross-linking interactions between GQDs and collagen solution.Non-cross-linked（control group）and cross-linked（EDC,GQDs,EDC+GQDs）collagen films were detected through ATR-FTIR spectroscopy from 4000 cm^-1to 500 cm^-1 to evaluate the interaction of molecular groups between GQDs and collagen.Each group comprised three collagen film samples（n=3）.Finally,based on the above experiments,the interaction mechanism between GQDs and collagen（covalent cross-linking/non-covalent cross-linking）was analyzed.Enzymatic Degradation of Collagen Films.The modified collagen membrane was immersed in collagenase solution for 24 hours（37℃）,and then micro HYP content assay kit was used for detected Relative enzymolysis degree.The relative enzymatic hydrolysability was calculated with 10 samples in each group（n=10）.Inhibition of Collagenase Activitycollagenase activity assay kit measures collagenase activity using a synthetic peptide（FALGPA）that mimics the structure of collagen to detected Collagenase Activity.This assay was performed in a 96-well plate,and five wells were replicated for each group（n=5）.Effect of GQDs on the durability of resin dentine bonding interface.The acid-etched and rinse adhesive system was used to evaluate the resin–dentin bond by microtensile bond strength,resin–dentin sticks with a cross-sectional area of approximately 1 mm²used universal testing machine to measure micro tensile strength.By in Situ Zymography of the HL to evaluate inhibition of matrix metalloproteinases.The micropermeability of the Resin–Dentin Interfaces were observed under laser confocal microscope by double fluorescence technique.Results:GQDs with the aid of EDC can cross-linked collagen via covalent bonds.GQDs could inhibit collagenase activity and improve the anti-enzymatic hydrolysis of collagen.In the resin–dentin adhesion model,theμTBS of the EDC+GQDs group was significantly higher than the other control groups after thermocycling.The addition of EDC to GQDs could inhibit matrix metalloproteinase activity and promote the integrity of the bonding interfaces after thermocycling.Conclusion This study proved that GQDs may cross-link collagen via noncovalent bonds and have relatively strong ability to inhibit collagenase activity,but the resistance enzymatic hydrolysis ability is relatively limited and unstable.GQDs combined with EDC can form covalent linkage with collagen fibers,improving the ability of resistance enzymatic hydrolysis of collagen fibers and inhibiting the activity of collagenase.GQDs with EDC as a primer using the acid-etched and rinse adhesive system,which may improve the bonding strength after thermocycling,inhibit MMP activity in situ and promote the integrity of the HL after thermocycling.Therefore,GQDs mediated by EDC can inhibit the hydrolysis of collagen fibers and improve the adhesion durability.