The Study Of Biological Properties With Nano- Hydroxyapatite/collagen/Mg-Ca Alloy Combined Scaffolds

ObjectiveStudy on the biocompatibility of combined scaffold materials of nano-hydroxyapatite/collagen(nano-HA/collagen,NHAC)and magnesium calcium alloy(Mg-1%Ca)in vitro cell experiments and the osteogenic effects on the preservation of dogs’ extraction sites.Methods1.The three Mg-Ca alloy bar(diameter 0.7mm,length 7mm)according to the distribution shape is inserted into the triangle cone NHAC(diameter 5mm,height 1cm),the surface morphology of the NHAC/Mg-Ca composite scaffold was observed under scanning electron microscope and the element composition on the surface of the material was detected by X-ray spectrometer.2.Mouse osteoblasts(MC3T3-E1)were cultured by indirect method according to ISO10993-5 in vitro experiments.The extract of NHAC/Mg-Ca scaffolds and NHAC were prepared according to the ratio of 200mg/1000μl of material/medium.After cultured MC3T3-E1 cells in the extracts for 24 hours,the growth of osteoblasts were observed under an inverted microscope;experimental testing of NHAC/Mg-Ca alloy stents and NHAC extract on the proliferation of MC3T3-E1 cell;Experimental testing of NHAC/Mg-Ca alloy stents and NHAC extract effect on MC3T3-E1 cell apoptosis by DAPI staining;by cell scratch assay of NHAC/Mg-Ca alloy stent and NHAC effects of extracts on MC3T3-E1 cell migration.3.In vivo animal experiment,6 dogs were extracted from fourth mandibular bilateral premolars,and 24 dental extraction sockets(12 mesial sockets and 12 distal sockets)were randomly divided into two groups: A and B.NHAC/Mg-Ca alloy scaffolds were implanted in group A,NHAC implanted in group B,and experimental dogs were sacrificed at 12 and 24 weeks after operation respectively.Tissue specimens were prepared and evaluated by gross observation,CBCT,biomechanical test,X-ray microscope,Hepatic and renal histological sections were used to evaluate the healing and osteogenesis of the tooth extraction and injury of liver and kidney.ResultsThe results of MTT showed that with the increase of incubation time,cell proliferation activity of NHAC/Mg-Ca stent group and NHAC group were increased,osteoblasts cultured in the NHAC/Mg-Ca stent group extracts in 1,3 and 5 days showed similar light absorption value(OD)compared with that in NHAC group and blank control group,and the difference was not statistically significant(P>0.05).The results of cell scratch test showed that the cells in the NHAC/Mg-Ca group had similar cell migration ability with the NHAC group and the blank control group.The results of DAPI staining showed that there was no obvious cell disintegration in the NHAC/Mg-Ca scaffolds under the microscope.Animal experiments in vivo showed that two groups of materials gradually degraded and absorbed during the process of tooth socket healing,and new bone tissues were continuously formed.At 12 weeks after operation,the CBCT results showed that the relative bone density value of NHAC/Mg-Ca stent group was more than that of NHAC group(P<0.05).Compressive strength test results showed that the compressive strength of extraction tissue of NHAC/Mg-Ca stent group was greater than that of NHAC group,the difference was statistically significant(P<0.05).X-ray microscopy results showed that trabecular bone volume fraction in the NHAC/Mg-Ca scaffold group was larger than NHAC group in the region of interest,with significant difference(P<0.05).Liver and kidney tissue damage is not the same shape and normal liver and kidney tissue.At 24 weeks after operation,the number of nascent bone tissue in both groups gradually increased.The relative bone density value,compressive strength and trabecular bone volume fraction in the NHAC/Mg-Ca group and NHAC group were not significant(P>0.05).ConclusionThe NHAC/Mg-Ca combined scaffold materials have no cytotoxicity and can promote the proliferation and differentiation of osteoblasts in vitro.At the same time,NHAC/Mg-Ca combined scaffold material can be used in the preservation process of dogs’ extraction socket.Because of its good biocompatibility and mechanical strength,it can promote the healing of the extraction socket and the formation of new bone.It provides a new idea for the joint application of NHAC and magnesium alloy.