Study On Magnesium-based Calcium Phosphorus-Chitosan-Graphene Bone Material Based On SC-CO₂ Loading Drug

Objective Magnesium-based calcium-phosphorus-chitosan-graphene bone material by SC-CO₂ loading drug was prepared and characterized.Biodegradability,electrochemical corrosion resistance and the activity of the mouse osteoblasts 3T3E1 in vitro for this bone material were investigated.Methods Aspirin?ASA?was loaded on the graphene oxide?GO?by the physical method and SC-CO₂?supercritical CO₂?technology.The aspirin content in GO was calculated by UV spectrophotometry.The optimum drug-loading conditions and the maximum drug-loading amounts for two methods were determined,and GO-ASA complex at the optimal condition was obtained.Subsequently,magnesium-based calcium-phosphorus-chitosan,magnesium-based calcium-phosphorus-chitosan-graphene/aspirin by the physical loading and magnesium-based calcium-phosphorus-chitosan-graphene/aspirin by SC-CO₂ loading were respectively prepared by the electrophoretic deposition.Three different coatings on magnesium matrix were analyzed and characterized by infrared spectroscopy?FT-IR?and X-ray diffraction?XRD?.The microstructures of three different coatings were analyzed by scanning electron microscopy?SEM?.The bioactivity and degradation behaviour of magnesium-based calcium phosphorus-chitosan,magnesium-based calcium-phosphorus-chitosan-graphene/aspirin by the physical loading and magnesium-based calcium-phosphorus-chitosan-graphene/aspirin by SC-CO₂loading were investigated by the immersion experiment.The CCK-8 method was used to detect the effects of different immersion liquids and coatings on the proliferation of the mouse osteoblasts 3T3E1 in vitro.Results Aspirin was loaded on GO by the physical method,the optimum technological parameters were loading time of 2 h,loading temperature of 20°C,and the mass ratio of GO and aspirin of 1:1.Under the above condition,the drug-loading amount was 0.0363mg/mg.The optimum technological conditions for SC-CO₂ loading were supercritical pressure of 20 Mpa,supercritical temperature of 40°C,supercritical time of 1 h,and the ASA/GO ratio of 2:1,the drug loading capacity in GO was 0.1210 mg/mg at this condition.The main components of the ceramic coating on the magnesium matrix were HA and HCA,and the drug loading amount of the calcium phosphate-chitosan-graphene/aspirin coating by SC-CO₂ loading was higher than that of the calcium phosphate-chitosan-graphene/aspirin by the physical loading.The deposition process of HA and HCA in the coating was greater than their dissolution process when magnesium-based calcium phosphate-chitosan-graphene/aspirin by SC-CO₂ loading was soaked in m-SBF from 0 week to 6 weeks.When it was soaked from 6 weeks to 12 weeks,the dissolution process of HA and HCA in the coating was dominant.Magnesium-based calcium phosphate-chitosan-graphene/aspirin by SC-CO₂ loading was immersed in m-SBF from 1 weeks to 6 weeks,and the corrosion reaction was controlled by the electrochemical and finite layer diffusion processes,accompanied by the adsorption and detachment of corrosion products on the matrix.When it was soaked for 8 weeks,its corrosion reaction was controlled by electrochemistry and finite layer diffusion processes.The corrosion reaction was controlled by the charge transfer processes and semi-infinite diffusion process when immersing from 10 weeks to12 weeks.The results of cell proliferation experiments showed that the cell proliferation rate was the highest under the soaking solutions of 50%and the soaking time of 2 weeks for magnesium-based calcium phosphorus-chitosan,magnesium-based calcium phosphorus-chitosan-graphene/aspirin by the physical loading and magnesium-based calcium phosphorus-chitosan graphene/aspirin by SC-CO₂ loading.With the immersion solution as the cell culture medium,the maximum proliferation rate was 46%when the incubation time of the immersion solution reached 20 hours for magnesium-based calcium-phosphorus-chitosan,and the maximum proliferation rate was 55%and 71%respectively for magnesium-based calcium-phosphorus-chitosan-graphene/aspirin by the physical loading and SC-CO₂ loading when the incubation time of the immersion solution was 24hours.With the coating as the growth matrix,the cell proliferation rate increased with the culture time for the calcium phosphorus-chitosan coating group,calcium phosphorus-chitosan-graphene coating group,calcium phosphorus-chitosan-graphene/aspirin coating by the physical loading group and calcium phosphorus-chitosan-graphene/aspirin coaitng by SC-CO₂ loading group,the cell proliferation rates of the four coatings were respectively71%,78%,142%and 185%when the culture time was 48 hours.For calcium-phosphorus-chitosan-graphene/aspirin coating by the physical loading group and calcium-phosphorus-chitosan-graphene/aspirin coating by SC-CO₂ loading group,the cell proliferation rate could reach 152%and 192%when the culture time was prolonged to 3 days.Conclusions Compared with the physical method,the drug loading amount in GO by SC-CO₂ technology significantly increased,which was because the characteristics of high diffusion and disappearance of gas-liquid interface for SC-CO₂ were beneficial to the drug loading.The prepared magnesium-based calcium phosphate-chitosan-graphene/aspirin by SC-CO₂ loading bone material showed the excellent biological activity and suitable degradation rate,and it could promote the proliferation of the mouse osteoblasts 3T3E1and show the osteogenesis.