Preparation And Characterization Of Injectable Drug-loaded Porous Magnesium Phosphate-based Bone Cement

The size range and connectivity of the pore are the key factors to affect the formation,repair and regeneration of bone,the adhesion,migration and expression of cells and the ingrowth of tissue.Therefore,how to build a porous structure is one of the important researches in bone repair material.On the other hand,drug treatment is required in the treatment of inflammation or curettage of bone tumors after the implant of material.Currently,it is difficult for the porous material to shape and the traditional drug treatment has the problem of systemic toxicity.So magnesium-based bone cement was combined with the drug-loaded gelatin microspheres（GMs）,and the drug was packaged in the gelatin microspheres to reduce toxicity.In the end,the drug-loaded magnesium phosphate bone cement was built by using the gradual degradation,release of the drug of the GMs and the advantages of high plasticity of magnesium phosphate bone cement.Magnesia（MgO）,potassium dihydrogen phosphate（KH₂PO₄）,calcium dihydrogen phosphate（Ca（H₂PO₄）₂）were used as solid components in the paper,and deionized water as liquid phase component.And the effects of different composition of solid phase on setting time,compressive strength,extract pH,degradation rate and biocompatibility were discussed.The results showed that with the increase of KH₂PO₄ or Ca（H₂PO₄）₂,the extract pH decreased from 7.8 to 7.1,the compressive strength increased first and then decreased,and the maximum value was 32Mpa,the setting time extended from 6min to 38min,the degradation rate went on with time.Moreover,the MPBC possessed good biocompatibility and injectable performance.Emulsification cross-linking method was applied to prepare drug-loaded gelatin microspheres.We talked over influences about the content of Span-80,rotating speed,gelatin solution volume on particle size of gelatin microspheres.What’s more,natural non-toxic glucose replaced glutaraldehyde to be the crosslinking agent,its effects on drug loading efficiency,encapsulation efficiency and particle size were also discussed.The results were that the content of Span-80 had little effect on particle size,while with the faster the rotating speed and the more volume of gelatin solution,the diameter was smaller.And when the Span-80 was 3ml,volume of gelatin solution4.5ml,the rotating speed 200r/min,we could get the gelatin microspheres with particle diameter in 100-300μm.At last,the glucose concentration was chosen to be0.5g/ml,the volume 1ml,rotating speed 400r/min,Span-80 3ml,volume of gelatin solution 4.5ml,and 2g solid gelatin contained 1g drug.The drug loading and encapsulation efficiency turned out as 26.73%and 32.86%.Particle size between500-700μm,300-500μm,100-300μm,less than 100μm respectively possessed percentage of 3.54%,37.95%,57.31%and 1.20%.Then MPBC was combined with drug-loaded gelatin microspheres.The effects of different content of drug-loaded gelatin microspheres on compressive strength,porosity and drug delivery rate were studied.And the outcome was that the compressive strength increased with the increase of drug-loaded gelatin microspheres,and the maximum rises was 87.6%.While the porosity decreased.With time,the compressive strength decreased gradually,while the porosity increased.And the porosity was 81.3%,the compressive strength was 7.97Mpa after degradation for 28days,the drug release rate was 88.9%after 7 days when the drug-loaded gelatin microspheres mass ratio was 8%in the bone cement.In this paper,a kind of porous magnesium phosphate-based bone cement material was produced successful by using the degradation of GMs.And the drug was loaded on the GMs to build the system of porous drug delivery,which may have the possibility to be a new kind of bone repair materials.