The Study Of ZIF-8 Modified GelMA Hydrogel For Alveolar Bone Regeneration

Background:Progressive resorption of alveolar bone is one of the main symptoms of periodontitis,which eventually leads to tooth loosening and loss.Pathogens in periodontal pocket can directly or indirectly cause alveolar bone resorption.At present,the strategy for the treatment of periodontitis is to remove the pathogenic factors and repair the defective alveolar bone.However,traditional periodontitis treatment methods such as supragingival cleaning,subgingival curettage,root planing and guided tissue regeneration（GTR）are difficult to effectively repair defective alveolar bone.Therefore,promoting alveolar bone regeneration is a research hotspot in the field of periodontitis treatment.In recent years,it has been found that ZIF-8,as a carrier of Zn²⁺,has the ability of antibacterial and promoting bone regeneration.GelMA has the characteristics of injectability and photopolymerizability,which can be filled in irregular periodontal pockets and crosslinked in situ.In this study,GelMA was used as a local drug carrier loaded with ZIF-8 to prepare multifunctional composite hydrogel（GelMA-Z）,which was expected to promote alveolar bone regeneration.Objective:1.ZIF-8 was synthesized by hydrothermal method,and GelMA-Z loaded with ZIF-8 was prepared.2.In vitro,the biocompatibility,osteogenic differentiation and antibacterial activity of GelMA-Z were evaluated.3.In animal experiment,the effect of GelMA-Z on alveolar bone regeneration in rats was further explored.Methods:1.Synthesis and haracterization of ZIF-8 and GelMA-Z:ZIF-8 was prepared by hydrothermal method.GelMA-Z was prepared by adding ZIF-8 to GelMA.The physicochemical of ZIF-8 and GelMA-Z were characterized by scanning electron microscope（SEM）,X-ray diffractometer（XRD）and Fourier transform infrared spectroscopy（FTIR）.The rheology of GelMA-Z and the release of Zn²⁺were detected by rotary rheometer and atomic absorption spectrophotometry（AAS）.2.Biocompatibility test:The hemolysis rate of GelMA-Z was detected by hemolysis test.In addition,rat bone marrow mesenchymal stem cells（rBMSCs）were cocultured with GelMA-Z,and its biocompatibility was evaluated by CCK-8 kit,cell live/dead staining kit and TRITC-Phalloidin/DAPI staining.3.Osteogenic ability test in vitro:rBMSCs were cocultured with GelMA-Z,and the osteogenic ability in vitro was evaluated by ALP activity assay,alizarin red staining,Real-time PCR to detect the expression of osteogenesis-related genes（Alp,Runx2,Col1 and Ocn）and Western blot to detect the expression of osteogenesis-related proteins（RUNX2 and OCN）.4.Antibacterial ability test in vitro:Porphyromonas gingivalis were cocultured with GelMA-Z,and the antibacterial activity of GelMA-Z was detected by plate bacteriostasis test and live/dead staining of bacteria.5.Animal experiment:The rat model of periodontitis was established,and the ability of GelMA-Z to promote alveolar bone regeneration in rats was detected by Micro-CT and histological staining.Results:1.ZIF-8 was successfully synthesized and loaded into GelMA.GelMA-Z has the characteristics of injectability and photopolymerizability.GelMA-Z could stably release Zn²⁺within 14 days.2.The hemolysis test results showed that the hemolysis rate of GelMA-Z was less than 5%.CCK-8 and cell live/dead staining showed that the cell viability in GelMA-Z was more than 80%,and there were almost no dead cells in each group.TRITC-Phalloidin/DAPI staining showed that rBMSCs displayed normal morphology on GelMA-Z.The above results confirmed that GelMA-Z had good biocompatibility.3.After rBMSCs were cocultured with GelMA-Z for a period of time,compared with gelma,the Alp activity,the number of calcium nodules,the expression levels of osteogenesis related genes（Alp,Runx2,Col1 and Ocn）and proteins（RUNX2 and OCN）of rBMSCs in GelMA-Z increased with the increase of ZIF-8 content.The above results confirmed that GelMA-Z could promote the osteogenic differentiation of rBMSCs in vitro.4.Bacterial growth curve and plate bacteriostatic experiment showed that GelMA-ZH had remarkable bacteriostatic ability.Furthermore,the live/dead staining of bacteria proved that GelMA-ZH could effectively kill bacteria.The above results confirmed that GelMA-Z had antibacterial ability against Porphyromonas gingivalis.5.Animal experiments showed that GelMA-ZH could significantly promote alveolar bone regeneration in rat periodontitis model.Conclusion:In this study,an injectable and photopolymerizable composite hydrogel（GelMA-Z）was prepared.Under UV irradiation,GelMA-Z solution was rapidly crosslinked and transformed into gel.GelMA-Z could stably release Zn²⁺and had good biocompatibility.In vitro,GelMA-Z could promote the osteogenic differentiation of rBMSCs and had significant antibacterial activity against Porphyromonas gingivalis.In the rat model of periodontitis,GelMA-Z could promote the regeneration of defective alveolar bone.GelMA-Z has good prospect in the treatment of periodontitis.