Construction And Properties Of Multi-functional Calcium Phosphate Cement Through Ions Doping And Bioactive Substance Loading

It's well known that some trace elements have outstanding promoting effects on the physical-chemical and biological properties of bone repairing biomaterials,as well as some bioactive substance.In this study,multi-functional calcium phosphate cements?CPC?were synthesized through mono-ion doping,multi-ions doping,and the loading of bioactive protein,respectively.The bone regeneration effect of CPC on clinical will be improved after the enhancement of both the physical-chemical properties and biological properties.Fe³⁺-doped PCCP powder,one of the components of Fe-CPC,was synthesized via chemical precipitation method,and the crystal morphology was changed as the varying of Fe³⁺ content.The compressive strength and injectability of CPC were improved significantly after Fe³⁺ doping,with the sacrifice of setting time.No changing of hydration products was observed,and the hydration reaction was promoted with the existence of Fe³⁺.There were lots of needle-like crystals in Fe-CPC and more compact inner structure appeared after 3 days hydration.The doping of Fe³⁺ endowed Fe-CPC superparamagnetism,which will broaden the clinical application of CPC.The surface negative charge of Fe-CPC increased as the increasing of Fe³⁺ amount.The mBMSCs on Fe-CPC disks showed better attachment morphology and cell viability,higher cell proliferation rate and ALP activity,and more expression amount of osteogenic-related genes?COL-I,OPN,and Runx-2?.Cell behavior was related to the concentration of Fe³⁺.Owing to the surface negative charge and regular surface morphology,m BMSCs on Fe-CPC disks presented better adhesion and spreading.The concentration of released Fe³⁺ on the exactly surface area of Fe-CPC was the highest,which,however,couldn't be detected.In order to study the effect of Fe³⁺ concentration on cell behavior,a series of leaching liquid that has different concentrations of Fe³⁺ was prepared in this study.The performances of m BMSCs and HUVECs cultured in Fe³⁺-extracts showed increased proliferation rate in certain amount of Fe³⁺?0-12.7 ?g/L?.Osteogenesis and angiogenesis induced by Fe³⁺ were observed,but cytotoxicity in m BMSCs appeared when the concentration of Fe³⁺ was beyond a critical value.The osteogenesis of Fe-CPC was further improved with the loading of lactoferrin.The existence of lactoferrin had no influence on hydration products.The setting time extended and the compressive strength decreased after the loading of lactoferrin into Fe-CPC.The releasing rate of lactoferrin slowed down as the increasing of Fe³⁺ amount in Fe-CPC.It had been proved that Fe³⁺ and lactoferrin had synergistic effect on the osteogenic differentiation of m BMSCs.Moreover,Fe-CPC with lactoferrin had the function of inhibiting cell apoptosis,and more lactoferrin showed better inhibiting effect.Si and Zn co-doped CPC was synthesized with the adding of zinc silicate?ZS?into CPC.The compressive strength of ZS/CPC was gradually enhanced with the increasing of ZS content,however,with the sacrifice of setting time.The hydration rate of CPC was retarded because of the inhibition effect of Si and Zn on the growth of HA crystals.The steady release behavior of Ca,Si,and Zn from ZS/CPC was observed,and there was positive correlation between release amount and ZS content.Owing to the released ions,mBMSCs showed enhanced cell proliferation and osteogenesis and HUVECs showed better cell behavior and up-regulated angiogenic-related genes expression.As we all know,CPC has very slow degradation rate in vivo,which mismatches the growing rate of new bone.PLGA microspheres with diameter of 53-212 ?m were added into ZS/CPC to achieve fast-degrading CPC.The addition of PLGA microspheres had negative effect on the setting time and compressive strength of ZS/CPC.However,the degradation rate was significantly enhanced,and the degradation amount was over 30 wt.% after 8 weeks soaking in Tris-HCl solution in vitro.Micro-CT analysis presented uniformly distribution of PLGA microspheres,which meant there would be uniform pores in ZS/CPC after the degradation of PLGA microspheres.The PLGA microspheres loaded ZS/CPC was implanted into femur bone defects of New Zealand white rabbits for 4 and 16 weeks.The micro-CT analysis showed the gradual degradation of materials.The histological examination?HE stain and Masson stain?of femur bone defects showed that new bone grown along with the degradation pores of PLGA microspheres and the addition of ZS apparently increased new bone growing amount.