Osteoporotic bone recovery by a bamboo-structured bioceramic with controlled release of hydroxyapatite nanoparticles

While most bone defects can be repaired spontaneously,the healing process can be complicated due to insuf-ficient bone regeneration when osteoporosis occurs.Synthetic materials that intrinsically stimulate bone for-mation without inclusion of exogenous cells or growth factors represent a highly desirable alternative to current grafting strategies for the management of osteoporotic defects.Herein,we developed a series of hydroxyapatite bioceramics composed of a microwhiskered scaffold(wHA)reinforced with multiple layers of releasable hy-droxyapatite nanoparticles(nHA).These novel bioceramics(nwHA)are tunable to optimize the loading amount of nHA for osteoporotic bone formation.The utility of nwHA bioceramics for the proliferation or differentiation of osteoporotic osteoblasts in vitro is demonstrated.A much more compelling response is seen when bioceramics are implanted in critical-sized femur defects in osteoporotic rats,as nwHA bioceramics promote significantly higher bone regeneration and delay adjacent bone loss.Moreover,the nwHA bioceramics loaded with a mod-erate amount of nHA can induce new bone formation with a higher degree of ossification and homogenization.Two types of osteogenesis inside the nwHA bioceramic pores were discovered for the first time,depending on the direction of growth of the new bone.The current study recommends that these tailored hybrid micro/nano-structured bioceramics represent promising candidates for osteoporotic bone repair.

Nano Calcium-Deficient Hydroxyapatite/O-carboxymethyl Chitosan-CaCl_(2) Microspheres Loadedwith RheinforBone Defect Repair

Glutaraldehyde(GA),the most widely used crosslinking agent for biomaterials,is cytotoxic.CaCl_(2) is of particular interest due to its non-toxic nature.Rhein can chelate Ca^(2+)and promote bone growth.Here we reported a novel nano calcium-deficient hydroxyapatite/O-carboxymethyl chitosan-CaCl_(2) microspheres loaded with rhein(RH-nCDHA/OCMC-CaCl_(2) microspheres)using CaCl_(2) as crosslinking agent for bone defect repair.The obtained microspheres were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),thermogravimetric analysis(TG)and Fourier transform infrared spectroscopy(FT-IR).The surface of the obtained microspheres is rough with quite a few voids.The nano calcium-deficient hydroxyapatite(nCDHA)accounts for about 70% of the total weight of the microspheres,which is equivalent to the proportion of inorganic substances in human bones.A high encapsulation efficiency(EE)and loading capacity(LC)of the microspheres loaded with rhein was 90.20±0.60% and 11.03±0.30%,respectively.For microspheres using CaCl_(2) in simulated body fluid(SBF)after 14 days,the drug released continuously and bone-like apatite formed like layer.The cells on the surface of the RH-nCDHA/OCMC-CaCl_(2) microspheres grew better comparing with nCDHA/OCMC-GA microspheres and the skull defects of rats after landfill can be almost repaired after 8 weeks,which revealed the potential of the microspheres for bone repair.