IADR Abstract Archives
Adding MMP20 to Amelogenin-Chitosan Hydrogel Improves Biomimetic Enamel Repair
Objectives: We recently demonstrated that an amelogenin-chitosan (CS-AMEL) hydrogel is effective at forming an enamel-like layer on etched tooth surfaces with a robust interface. However, the mechanical properties of newly grown layer were compromised by the presence of organic materials. We further showed that matrix metalloproteinase-20 (MMP20) plays a critical role in preventing protein occlusion inside enamel crystals. Objectives: To test our hypothesis that addition of MMP20 to CS-AMEL hydrogel could reinforce the newly grown layer by preventing amelogenin occlusion inside apatite crystals. Our aims were i) to analyze the proteolytic processing of amelogenin by MMP20 in the presence of chitosan, and ii) to synthesize an enamel-like layer on etched enamel by applying the MMP20-containing (MMP20-CS-AMEL) hydrogel.
Methods: rhMMP-20 was added to the CS-AMEL hydrogel (Protein:MMP20 ratio = 1000:1) along with ZnCl2 solution (20µM). The etched enamel was treated with MMP20-CS-AMEL or CS-AMEL hydrogel as control and then immersed in artificial saliva solution at 37 °C. The MMP20 proteolysis of amelogenin was studied by High Performance Liquid Chromatography and Gel Electrophoresis. The morphology and composition of products were characterized using scanning electron microscopy, X-ray diffraction and Fourier Transform Infrared Spectroscopy. The mechanical properties of the newly grown layer were measured by Nanoindentation.
Results: Amelogenin was gradually degraded by MMP20 in the presence of chitosan. The newly grown crystals in the sample treated with MMP20-CS-AMEL hydrogel showed more uniform orientation, higher crystallinity and a greater length-to-thickness ratio than the samples treated with CS-AMEL hydrogel without MMP-20. The amount of protein observed in the repaired enamel was decreased by the addition of MMP20. Both the modulus and hardness of repaired enamel were significantly improved by the MMP20-CS-AMEL hydrogel.
Conclusions: Addition of MMP20 to CS-AMEL hydrogel improved the mechanical properties of a newly grown enamel-like layer by regulating crystal growth and preventing protein occlusion.
Methods: rhMMP-20 was added to the CS-AMEL hydrogel (Protein:MMP20 ratio = 1000:1) along with ZnCl2 solution (20µM). The etched enamel was treated with MMP20-CS-AMEL or CS-AMEL hydrogel as control and then immersed in artificial saliva solution at 37 °C. The MMP20 proteolysis of amelogenin was studied by High Performance Liquid Chromatography and Gel Electrophoresis. The morphology and composition of products were characterized using scanning electron microscopy, X-ray diffraction and Fourier Transform Infrared Spectroscopy. The mechanical properties of the newly grown layer were measured by Nanoindentation.
Results: Amelogenin was gradually degraded by MMP20 in the presence of chitosan. The newly grown crystals in the sample treated with MMP20-CS-AMEL hydrogel showed more uniform orientation, higher crystallinity and a greater length-to-thickness ratio than the samples treated with CS-AMEL hydrogel without MMP-20. The amount of protein observed in the repaired enamel was decreased by the addition of MMP20. Both the modulus and hardness of repaired enamel were significantly improved by the MMP20-CS-AMEL hydrogel.
Conclusions: Addition of MMP20 to CS-AMEL hydrogel improved the mechanical properties of a newly grown enamel-like layer by regulating crystal growth and preventing protein occlusion.