Effects of low-intensity pulsed ultrasound stimulation on porous hydroxyapatite blocks for posterolateral fusion of lumbar spine in rabbits

he effects of porous hydroxyapatite blocks（PHABs） and an adjunct low-intensity pulsed ultrasound stimulation（LIPUS） on the fusion rate in a rabbit spinal posterolateral fusion（PLF） model were evaluated.Twenty rabbits underwent PLF with autograft and PHABs were randomly assigned to two groups：treated group with 20 min LIPUS daily and untreated control group for 4 weeks until euthanasia.The fused motion segments were subjected to manual palpation,gross observation,and radiographic investigation before histomorphologic and scanning electron microscopic analyses.Statistical differences between the LIPUS group and the control group are found in the fusion rate,bone density gray scale,trabecular bone formation,osteoblast-like cells,chondrocytes and positive expression of BMP-2 and TGF-β1 in the junction zone（significance level p〈0.05）.The results suggest that LIPUS can increase fusion rates and accelerate bone in-growth into PHAB.Hence,PHAB and LIPUS may be used together to increase fusion rates in a rabbit spinal fusion model with a promising extension to human application.

Fabrication and characterization of hierarchical porous Ni2+doped hydroxyapatite microspheres and their enhanced protein adsorption capacity

Hydroxyapatite(HAP)is a common bio-adsorbent,which performance depends heavily upon its morphology and microporous structure.In this study,a novel synthesis strategy was proposed for hierarchical porous HAP microspheres by a simple"one-pot"hydrothermal reaction.In the strategy,L-glutamic acid serves as soft template to modulate the morphology and inner crystalline of HAP.To evaluate the application potential,doping Ni^(2+) on hierarchical porous HAP microspheres gives metal chelated affinity adsorbents.The prepared adsorbents show a perfect spherical shape,particles size of 96.6μm,relatively specific surface area of 48.5 m^(2)·g^(-1) and hierarchical pores(mesopores:4 nm and macropores:53 nm).By the adsorption evaluation,it reveals that the Ni^(2+)-HAP adsorbents have high adsorption capacities of275.11 and 97.55 m^(2)·g^(-1) for hemoglobin and bovine serum albumin,respectively,which is comparable to other similar adsorbent.Therefore,this work provides a promising method for high-efficiency hydroxyapatite microspheres for proteins purification.

Preparation of multigradient hydroxyapatite scaffolds and evaluation of their osteoinduction properties

Porous hydroxyapatite(HA)scaffolds are often used as bone repair materials,owing to their good biocompatibility,osteoconductivity and low cost.Vascularization and osteoinductivity of porous HA scaffolds were limited in clinical application,and these disadvantages were need to be improved urgently.We used water-in-oil gelation and pore former methods to prepare HA spheres and a porous cylindrical HA container,respectively.The prepared HA spheres were filled in container to assemble into composite scaffold.By adjusting the solid content of the slurry(solid mixture of chitin sol and HA powder)and the sintering temperature,the porosity and crystallinity of the HA spheres could be significantly improved;and mineralization of the HA spheres significantly improved the biological activity of the composite scaffold.The multigradient(porosity,crystallinity and mineralization)scaffold(HA-700)filled with the mineralized HA spheres exhibited a lower compressive strength;however,in vivo results showed that their vascularization ability were higher than those of other groups,and their osteogenic Gini index(Go:an index of bone mass,and inversely proportional to bone mass)showed a continuous decrease with the implantation time.This study provides a new method to improve porous HA scaffolds and meet the demands of bone tissue engineering applications.

A Green Biocompatible Fabrication of Highly Porous Functional Ceramics with High Strength and Controllable Pore Structures

A green biocompatible foaming method utilizing natural coconut oil and cornstarch was developed to fabricate highly porous functional ceramics with controllable strengths and pore structures. The poros- ity of A1203 ceramics prepared via this method reached 79.6%-86.9% while these ceramics maintained high compressive strengths of 2.2-5.5 MPa. More importantly, porous A1203 ceramic with a pore size gra- dient was also readily fabricated by casting serial layers of foams that were set for different time periods. The potential applications of porous Al2O3 and HA ceramics fabricated by this green foaming method in- cluding scaffolds for oil cleaning and cell culture, respectively, were also demonstrated.

Vital role of hydroxyapatite particle shape in regulating the porosity and mechanical properties of the sintered scaffolds

The effect of particle shape on the porosity and compressive strength of porous hydroxyapatite （HA） scaffolds was investigated by sintering the mixture of rod-shaped HA （r-HA） and spherical HA （s-HA） with polyacrylamide used as the sacrificial template. It was found, for the first time, that addition of r-HA into s-HA could exponentially decrease the porosity of sintered HA scaffolds and enhance their compressive strength with the increase of r-HA content. The mechanism, according to the results from scanning electron microscopy and X-ray diffraction, lies in the restriction of s-HA to the grain formation and growth of r-HA during sintering and results in the fusion of r-HA with s-HA. These findings suggest that mixture of r-HA and s-HA might provide a new and facile way to improve the compressive strength of oorous HA scaffolds.