| Research Purpose and SignificanceDue to its biological inertia,facile processing and erosion and abrasion resistance,silicone rubber(SR)has been widely applied in the medical field since the 1970 s.It has become one of the most common soft tissue biomaterial fillings used to restore pectoral or facial disfigurements caused by congenital abnormalities,trauma or cancer resection.However,there are still some critical concerns that hamper the application of SR as a biomaterial implant for long-term utilisation in the body.Due to non-polarity,the R-group of SR is arranged on the outside of the spiral structure,which causes the silicone material to exhibit strong hydrophobicity.After being implanted in the body,a fibrous capsule can easily form around the implanted material due to poor compatibility with the cell and tissue;this can cause the implant to deform,translocate and even become exposed.Further,some patients can experience prolonged fever due to granuloma after silicone implantation,which is related to the local effects of SR's high surface hydrophobicity and poor biocompatibility,this limits the affinity of mammalian cells to effectively adhere to the native SR surface.In order to improve this phenomenon,in the early work of the research group,the light water group carboxyl(-COOH)was introduced into silicone rubber to prepare POSS-COOH / SR nano hybrid materials.It was found that the introduction of POSS-COOH successfully reduced the thickness of the coating around the SR material.In the previous work,it was found that the coating thickness of POSS-COOH/SR decreased,but the mechanism was not clear.Sarantos Papadopoulos et al.found that fat filling can effectively treat capsular contracture,relieve pain,improve skin quality and breast sensation,so we proposed the hypothesis: POSS-COOH/SR is related to the differentiation of some cells.Mesenchymal stem cell(BMSC)is an important member of stem cell family,which has the function of self-renewal and pluripotent differentiation.Therefore,this paper studies the effect of POSS-COOH/SR on the adhesion,proliferation and differentiation of bone marrow mesenchymal stem cells.It provides a theoretical basis for the formation of capsular contracture on the surface of silicone rubber breast prosthesis,and also provides a new idea for the treatment of capsular contracture on the surface of silicone rubber breast prosthesis.Research methodPart I: Preparation of POSS-COOH/SR nanocomposites and SRPrepare natural silicone rubber by using two-component medical liquid silicone rubber at room temperature.After standing and solidifying at room temperature.On the electronic scale,0.01-0.05 g POSS-COOH was mixed with rubber A for 5 ml 30 min,then added with rubber B for 5 ml.After being mixed evenly and injected into the metal flat grinding tool,vulcanized and solidified for 6 hours,the POSS-COOH/SR and the ordinary SR experimental diaphragms with different proportions of 0.1%-0.5% were made.Part II: Surface morphology and physical and chemical properties of POSS-COOH/SR and SRSurface morphology and physicochemical properties of ordinary SR and POSS-COOH/SR nanocomposites with different ratios from 0.1% to 0.5% were measured and evaluated by means of Scanning Electron Microscopy(SEM),Atomic Force Microscopy(AFM),A-type Shaw hardness tester,Raman spectroscopy and water contact angle analysis.SPSS20.0 was used for statistical analysis.Part III: The effects of POSS-COOH/SR on the adhesion,proliferation and differentiation of rat bone marrow mesenchymal stem cells1.Cell preparation: Sprague Dawley female rat bone marrow mesenchymal stem cells(rBMMSCs)were isolated,purified and identified for subsequent experiments.2.Experimental grouping:1)Ordinary SR was used as control group.Rat bone marrow mesenchymal stem cells were cultured on the surface of SR material.2)0.1%-0.5% POSS-COOH/SR nanocomposites were used as experimental group.RBMSCs were cultured on the surface of each group of materials,and the effects of each group of materials on the adhesion,proliferation and differentiation of rBMMSCs were observed.3.Laser confocal,WB,etc.were used to observe the expression of cell adhesion proteins on the surface of the modified materials,and MTT was used to understand the value-added and activity of mesenchymal stem cells on the surface of the materials,so as to evaluate the biological safety of the modified silica gel materials.4.Cells were cultured on the surface of each group for 21 days,then the cultured cells were stained with oil red O,alizarin red S and alizarin blue.5.Laser confocal,WB and q-PCR were used to further confirm the differentiation of mesenchymal stem cells from cell,protein and gene levels.Experimental result1.POSS-COOH/SR nanocomposites with 0.1%-0.5% were successfully prepared.2.The surface morphology of the modified material was scaned by SEM.It was found that there were irregular grooves on the surface of ordinary SR and different proportions of POSSCOOH/SR,which was caused by the change of room temperature during the curing process of liquid silicone rubber and had nothing to do with the filling of POSS-COOH nanoparticles.The experimental results of AFM confirmed once again that the surface morphology of nanocomposites and SR was smooth and no hilly change after protuberance.3.The results of Shaw hardness test show that the hardness of POSS-COOH decreases gradually with the increase of POSS-COOH ratio in SR.4.The water contact angle of modified POSS-COOH/SR nanocomposites is significantly lower than that of SR,but there is no significant difference between different proportions.It shows that the hydrophobicity of SR materials can be reduced by the blending of POSS-COOH and SR.5.The results of WB and laser confocal showed that the adhesion of the modified nanocomposites increased,especially on POSS-COOH/SR composites with the ratio of 0.3% to 0.5%,the cell-related adhesion protein equivalent was significantly higher than that of the stem cells on the surface of ordinary SR.6.Staining showed that SR and the modified nanocomposites had no obvious osteogenic and chondrogenic differentiation,but the modified nanocomposites had the ability of lipid differentiation.The lipid differentiation and concentration of the modified nanocomposites showed an inverted "U" type change,i.e.the greatest ability of lipid differentiation was at 0.3% concentration.7.With WB,laser confocal and q-PCR,the expression of PPAR?,a marker of adipogenesis,was confirmed at cellular,protein and gene levels.8.MTT test results showed that the rBMMSCs activity on the surface of POSS-COOH/SR nanocomposites was worse than that on the surface of SR,which proved that POSS-COOH/SR nanocomposites had a significant inhibitory effect on the proliferation of rBMMSCs.Conclusion1.POSS-COOH/SR nanocomposites are easy to fabricate,easy to process and feasible.The interface physical and chemical properties of the nanocomposite are stable,which not only keeps the biological inertia,corrosion resistance and easy processing of SR itself,but also introduces the hydrophilicity of-COOH,so as to improve the hydrophobicity of silicone rubber.2.Although-COOH can induce chondrogenic differentiation of mesenchymal stem cells,the experimental results show that the modified nanocomposites have a tendency to induce rBMMSCs to differentiate into adipocytes,and no chondrogenic differentiation of stem cells is observed.3.With the increasing proportion of POSS-COOH in SR,the hardness of the modified nanocomposites becomes lower and lower.POSS-COOH has the ability to change the hardness of SR,and the concentration is inversely proportional to the hardness.4.The adhesion of cells on POSS-COOH/SR surface was enhanced,but the proliferation of cells on the surface of materials was inhibited to some extent. |
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