Preparation Of Metformin Carbon Dots Loaded CH/SF Sustained Release Microspheres And Its Toxicity To Human Pulp Cells

Background:In the process of root development of young permanent teeth,the characteristics of their anatomical morphology and tissue structure are easily affected by caries,trauma and other factors,which may cause pulpal and periapical disease.Root canal therapy is not conducive to the root development and long-term retention of young permanent teeth,so vital pulp therapy is often used clinically.However,the existing pulp capping materials have many problems,and new pulp capping agents need to be developed.In recent years,carbon dots,as a kind of nanomaterial,have attracted the attention of researchers due to their low toxicity,fluorescence properties and potential osteogenic/odontogenic effects.Microsphere embedded the drugs in the matrix of the polymer materials,forming a kind of solid sphere,which has good slow-release effect.As natural biological materials,silk fibroin and chitosan have the advantages of good biocompatibility,biodegradability and low cost,and are rich in hydroxyl and amino,which can form hydrogen bond and chemical bond with drugs,so they are ideal carrier materials.In this study,metformin carbon dots was prepared and metformin carbon dots loaded chitosan/silk fibroin microspheres sustained-release system(MCDs-CS/SF-MPs)was constructed to detect the sustained-release of metformin carbon dots and the cytotoxicity of the microspheres on human dental pulp stem cells(h DPCs)in vitro.Objective:To investigate the optimal process conditions for the preparation of MCDs-CS/SFMPs by orthogonal experiment,and to evaluate its sustained-release effect of metformin carbon dots and cytotoxicity to h DPCsin vitro.Methods:1.Hydrothermal method was used to synthesize metformin carbon dots and characterize them.2.Emulsification method was used to prepare MCDs-CS/SF-MPs with genipin as a crosslinking agent.The optimal preparation process was selected through orthogonal experiment to prepare the optimal microspheres.First,its surface morphology,particle size,loading efficiency and encapsulation efficiency were investigated and characterized.Then,the sustained-release effect in vitro was measured.3.The extracted healthy and caries-free third molars were selected clinically,and h DPCs were extracted,passaged,and then subcultured4.CCK-8 was used to detect the cytotoxicity of MCDs-CS/SF-MPs,and the concentrations of microspheres were set as 0.75,1.5,2.25,and 3mg/m L.Results:1.High-resolution transmission electron microscopy showed that metformin carbon dots with a diameter of about 1.71±0.43 nm were successfully synthesized.Fourier transform infrared spectroscopy showed that metformin carbon dots contained abundant hydroxyl and amino groups.Fluorescence spectra of metformin carbon dots showed excitation dependent fluorescence properties,and the best excitation wavelength was 310 nm,and the best emission wavelength was 432 nm.2.Orthogonal experimental design was used to screen out the best microspheres prepared when the concentration of chitosan was 30mg/m L,the concentration of genipin was 5mg/m L,and the mass ratio of drug to carrier was 1:4.Scanning electron microscopy shows that MCDs-CS/SF-MPs prepared by the best technology were spherical with smooth surface,the particle size was about 2.24±0.52μm,the loading efficiency was 15.87±0.42%,and the encapsulation efficiency was 79.37±3.39%.Fourier infrared spectra and X-ray diffraction diagrams proved successful synthesis of MCDs-CS/SF-MPs,and the microspheres were released in vitro for up to 51 days and continued to be released.3.The primary h DPCs were irregularly radiated around the tissue mass.After passage,the h DPCs were long fusiform and arranged in a "vortex" or bundle.4.CCK-8 results showed that MCDs-CS/SF-MPs had a dose-dependent effect on the activity of h DPCs.The activity of h DPCs in the 3mg/m L group was significantly inhibited from the 3rd day,while the proliferation of h DPCs in the other concentration groups was promoted within seven days.Conclusion:MCDs-CS/SF-MPs prepared by the best technology were regular spherical,uniform in size,slightly adhesive,and had higher loading efficiency and entrapment efficiency.The microspheres had obvious sustained-release effect of metformin carbon dots,and has good biocompatibility.