Studies On Microsphere-type Bone Repairing Biomaterials With Strengthened Osteocompatibility Via Incorporation And Controlled Release Of Magnesium Ion And Icariin

Magnesium is the fourth most abundant metal element in human body,half of which is found in bone tissue.In natural bone,magnesium ions can enter hydroxyapatite(HA)lattice and directly affect bone density and bone mechanical properties.In recent years,researchers have conducted in-depth studies on the biological effects of magnesium ions and found that the certain concentrations of magnesium ions can promote the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells(BMSCs).However,high concentrations of magnesium ions can also cause significant cytotoxicity.Therefore,it is of guiding significance to integrate magnesium into bone tissue engineering scaffold materials,regulate the release of magnesium ions,and ensure the biosafety while promoting bone regeneration,for the application of magnesium in bone tissue engineering.However,the introduction of single bioactive substances often fails to achieve an ideal repair effect.In China,the use of traditional Chinese medicine for the treatment of bone defects has a history of thousands of years.However,the complexity of traditional Chinese medicine ingredients and the backwardness of basic research,especially the controlled release of the effective ingredients of traditional Chinese medicine,limit their application in bone tissue engineering.Icariin,an effective monomeric component of Epimedium,is a traditional herbal tonic from plants.It has been applied in the treatment of osteoporosis and proved to promote the osteogenic differentiation of BMSCs.Traditional scaffold materials for bone tissue engineering are often unavoidable in clinical use.With the development of minimally invasive surgery,biodegradable microspheres not only have good injectability,but also can provide a surface suitable for cell growth.Meanwhile,biodegradable microspheres are ideal controlled release carriers for bioactive components(such as growth factors,drugs,etc.).As a traditional biodegradable aliphatic polyester,poly(lactic acid)and its copolymers are widely used in the biomedical field due to their good biocompatibility and biodegradability.In this study,an injectable microsphere-type bone repair material with different magnesium ion release behaviors and co-release of icarin/Mg2+was prepared by emulsion solvent volatilization with poly(lactic acid-hydroxyacetic acid)as the matrix.The specific research was as follows:1.Using MgO and MgCO3 as Mg2+ sources,in this study,Mg-containing microspheres(PMg)were prepared from biodegradable PLGA,which readily achieved the goal of tunable Mg2+release behaviors via changing the ratios of encapsulated MgO and MgCO3.The PLGA microspheres serve as a reservior of Mg2+,from which,Mg2+ions were released gradually and stably resulting from the concurrent dissolution of MgO and MgCO3 by taking advantage of their different hydrolyzation rates.All the prepared Mg-containing microspheres were non-cytotoxic,supporting migration,attachment,proliferation and osteogenic differentiation of rat bone mesenchymal stromal cells(rBMSCs),in particular,they could beckon cells to move over with those released Mg2+ions.It was found that the PMg-? microspheres,which embedded MgO and MgCO3 in 1:1 weight ratio and demonstrated a sustained Mg2+ release upwards 28 days at a steady rate,exhibited the strongest ability in promoting the osteogenic differentiation of rBMSCs in comparison with other PMg microspheres containing higher or lower ratios of MgO and MgCO3.By injecting PMg-? microspheres into the critical-sized calvarial defect(?=8 mm)in rat model for 16 weeks,significant bone regeneration was identified without introducing other bioactive factors like exogenous cells or growth factors,while the control group filled with blank PLGA microspheres displayed much inferior outcomes.2.MgO and MgCO3 particles(1:1)were dispersed in Icariin(ICA)solution and lyophilized to obtain MgO/MgCO3-ICA(MI)particles.Then PLGA-MgO/MgCO3-ICA(PMI)composite microspheres were prepared by S\O\W emulsion method.The composite microspheres with different ICA release behavior,and through the collaborative control of ICA and Mg2+release,promote BMSCs proliferation and differentiation,critical-sized calvarial defect model also verified its in vivo biological safety and ability to promote bone regeneration,16 weeks post-operation,new bone volume(BV/TV)value of 41.3±4.6%,which is much better than PMg microspheres,confirm the synergistic effect of ICA and Mg2+ to promote bone regeneration.In this study,PMg microspheres with controllable Mg2+release were prepared for the first time,which verified the concentration dependence of Mg2+ in vivo and in vitro to promote bone bioactivity,especially bone formation ability,and provided a theoretical basis for the clinical application of magnesium containing bone tissue engineering scaffold materials.At the same time,the adsorption capacity of inorganic particles on drugs was utilized to combine traditional Chinese medicine for osteoporosis treatment with bone bioactive ions for the first time,and their synergistic effect on promoting bone regeneration was confirmed,providing a new strategy for the design of bone tissue engineering cell microcarriers.