Synthesis,Characterization And Related Properties Of Drug-Loaded Hydroxyapatite/Graphene Oxide/Chitosan Composite Microspheres

Hydroxyapatite（HA）,as a new type of biomaterial,has good biocompatibility,bioactivity,and excellent characteristics of ion exchange.It has been a research hotspot in the field of biomaterials and environmental functional materials.In this study,HA and graphene oxide（GO）were compounded,and composite microspheres were further prepared by the hard template method to improve drug loading efficiency.Meanwhile,HA,GO and chitosan（CS）were compounded,then emulsified and cross-linked to form microspheres,thus yielded drug-loaded microspheres with excellent load and release properties and good morphology.A series of techniques such as X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,Raman spectrometer（Raman）,field emission scanning electron microscope（FESEM）,scanning electron microscope（SEM）,X-ray photoelectron spectroscopy（XPS）,X-ray energy dispersive analyzer（EDX）,synchronous thermal analyzer（TG）,fully automatic specific surface area and porosity analyzer,and laser particle size analyzer were used to analyze and characterize the prepared samples.And the drug-loading performance was tested using Curcumin（Cur）as a drug-loading model.The drug-loading performance of the microspheres was also evaluated by the encapsulation efficiency and drug-loading capacity.The release curve was fitted to study the drug release performance and kinetic release model of the microspheres.Besides,cytotoxicity tests were performed on the microsphere materials with Chinese hamster ovary cell lines.With spherical calcium carbonate as a hard template,spherical hollow HA/GO composite microspheres were successfully prepared by ion exchange via hydrothermal method.The effects of different synthetic conditions on the preparation of composite microspheres were studied.The research shows that the reactant concentration of the system,the amount of GO,the amount of control agent,the hydrothermal reaction time and other factors largely affect the molding effect of microspheres.When the initial reactant concentration（Ca Cl₂and Na₂CO₃）is 0.3 mol/L,the amount of GO is 0.1 mg/m L,the amount of the control agent（citric acid）is 0.5 mol/L,and the hydrothermal reaction time is 6 h,well-formed hollow HA/GO composite microspheres were obtained,whose particle size is 5.1～7.7μm,and the pore size is about 40 nm.Meanwhile,it was found that the spherical structure could indeed increase the load of the drug,and that the drug encapsulation efficiency was（20.90±0.31）%and the drug loading was（2.95±0.19）%.Fitting and analyzing its release curve found that the in vitro release of HA/GO composite microspheres basically conforms to the first-order kinetic equation.In other words,the release rate of HA/GO-loaded drugs is proportional to the first-order power of the amount of the loaded drugs.Using template synthesized HA/GO composite microspheres as raw materials,HA/GO/CS composite drug-loaded microspheres were prepared by emulsion cross-linking method.The effects of different synthetic conditions on the preparation of microspheres and their drug loading properties were studied.Studies have shown that the morphology of microspheres is significantly affected by the proportion of raw materials,stirring speed,and water bath temperature.Basically,the larger the stirring speed,the smaller the particle size,and when the water bath temperature is 40°C,it tends to stick.The HA/GO/CS composite microspheres prepared at a water bath temperature of 25℃can have good morphology and uniformity.Besides,a core-shell structure of chitosan-coated HA/GO composite microspheres was formed.Through the drug loading performance test,when its drug encapsulation efficiency and drug loading are optimal,they can reach up to（57.34±1.20）%and（4.37±0.78）%respectively.Cytotoxicity tests showed that the composite microsphere material has no negative effect on cell proliferation,which means no cytotoxicity.With nano-HA/GO powder synthesized by one pot hydrothermal method as raw materials,n HA/GO/CS composite drug-loaded microspheres were prepared through emulsification and cross-linking process.The effect of the proportion of raw materials on the microsphere formation and drug loading performance was studied.As the ratio of n HA/GO increases,the surface of the microspheres becomes rougher and rougher,which shows a noticeable graininess.HA nanorod-shaped particles are distributed on the surface and inside of the composite microspheres,forming a lot of pore structures,which provide conditions for coating drugs.And an appropriate increase in the proportion of CS can improve the drug loading performance of the composite microspheres.The encapsulation efficiency and drug loading of the n HA/GO/CS composite microspheres may reach up to（27.08±0.35）%and（2.98±0.12）%respectively.Further,the cytotoxicity tests showed that the microsphere material has no negative effect on cell proliferation,i.e.no cytotoxicity.