Youwen Deng

Current Progress in Bioactive Ceramic Scaffolds for Bone Repair and Regeneration

Bioactive ceramics have received great attention in the past decades owing to their success in stimulating cell proliferation, differentiation and bone tissue regeneration. They can react and form chemical bonds with cells and tissues in human body. This paper provides a comprehensive review of the application of bioactive ceramics for bone repair and regeneration. The review systematically summarizes the types and characters of bioactive ceramics, the fabrication methods for nanostructure and hierarchically porous structure, typical toughness methods for ceramic scaffold and corresponding mechanisms such as fiber toughness, whisker toughness and particle toughness. Moreover, greater insights into the mechanisms of interaction between ceramics and cells are provided, as well as the development of ceramic-based composite materials. The development and challenges of bioactive ceramics are also discussed from the perspective of bone repair and regeneration.

A space network structure constructed by tetraneedlelike ZnO whiskers supporting boron nitride nanosheets to enhance comprehensive properties of poly(L-lacti acid) scaffolds.

In this study, the mechanical strength and modulus of poly(L-lacti acid) (PLLA) scaffolds were enhanced with the mechanical properties of boron nitride nanosheets (BNNSs) and tetraneedlelike ZnO whiskers (T-ZnOw). The adhesion and proliferation of cells were improved as well as osteogenic differentiation of stem cells was increased. Their dispersion statues in PLLA matrix were improved through a space network structure constructed by three-dimensional T-ZnOw supporting two-dimensional BNNSs. The results showed that the compressive strength, modulus and Vickers hardness of the scaffolds with incorporation of 1 wt% BNNSs and 7 wt% T-ZnOw together were about 96.15%, 32.86% and 357.19% higher than that of the PLLA scaffolds, respectively. This might be due to the effect of the pull out and bridging of BNNSs and T-ZnOw as well as the crack deflection, facilitating the formation of effective stress transfer between the reinforcement phases and the matrix. Furthermore, incorporation of BNNSs and T-ZnOw together into PLLA scaffolds was beneficial for attachment and viability of MG-63 cells. More importantly, the scaffolds significantly increased proliferation and promoted osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs). The enhanced mechanical and biological properties provide the potentials of PLLA/BNNSs/T-ZnOw scaffolds for the application into bone tissue engineering.

A nano-sandwich construct built with graphene nanosheets and carbon nanotubes enhances mechanical properties of hydroxyapatite-polyetheretherketone scaffolds.

A nano-sandwich construct was built by combining two-dimensional graphene nanosheets (GNSs) and one-dimensional carbon nanotubes (CNTs) to improve the mechanical properties of hydroxyapatite–polyetheretherketone (HAP–PEEK) scaffolds for bone tissue engineering. In this nano-sandwich construct, the long tubular CNTs penetrated the interlayers of graphene and prevented their aggregation, increasing the effective contact area between the construct and matrix. The combination of GNSs and CNTs in a weight ratio of 2:8 facilitated the dispersion of each other and provided a synergetic effect in enhancing the mechanical properties. The compressive strength and modulus of the scaffolds were increased by 63.58% and 56.54% at this time compared with those of HAP–PEEK scaffolds, respectively. The carbon-based fillers, pulling out and bridging, were also clearly observed in the matrix. Moreover, the dangling of CNTs and their entangling with GNSs further reinforced the mechanical properties. Furthermore, apatite layer formed on the scaffold surface after immersing in simulated body fluid, and the cells attached and spread well on the surface of the scaffolds and displayed good viability, proliferation, and differentiation. These evidence indicate that the HAP–PEEK scaffolds enhanced by GNSs and CNTs are a promising alternative for bone tissue engineering.

Liquid Phase Sintered Ceramic Bone Scaffolds by Combined Laser and Furnace

Fabrication of mechanically competent bioactive scaffolds is a great challenge in bone tissue engineering. In this paper, β-tricalcium phosphate (β-TCP) scaffolds were successfully fabricated by selective laser sintering combined with furnace sintering. Bioglass 45S5 was introduced in the process as liquid phase in order to improve the mechanical and biological properties. The results showed that sintering of β-TCP with the bioglass revealed some features of liquid phase sintering. The optimum amount of 45S5 was 5 wt %. At this point, the scaffolds were densified without defects. The fracture toughness, compressive strength and stiffness were 1.67 MPam1/2, 21.32 MPa and 264.32 MPa, respectively. Bone like apatite layer was formed and the stimulation for apatite formation was increased with increase in 45S5 content after soaking in simulated body fluid, which indicated that 45S5 could improve the bioactivity. Furthermore, MG-63 cells adhered and spread well, and proliferated with increase in the culture time.

Improvement of the mechanical properties and corrosion resistance of biodegradable β-Ca3(PO4)2/Mg-Zn composites prepared by powder metallurgy: the adding β-Ca3(PO4)2, hot extrusion and aging treatment

In this study, 10%β-Ca3(PO4)2/Mg-6%Zn (wt.%) composites with Mg-6%Zn alloy as control were prepared by powder metallurgy. After hot extrusion, the as-extruded composites were aged for 72h at 150°C. The effects of the adding β-Ca3(PO4)2, hot extrusion and aging treatment on their microstructure, mechanical properties and corrosion resistance were investigated. The XRD results identified α-Mg, MgZn phase and β-Ca3(PO4)2 phase in these composites. After hot extrusion, grains were significantly refined, and the larger-sized β-Ca3(PO4)2 particles and coarse MgZn phases were broken into linear-distributed β-Ca3(PO4)2 and MgZn phases along the extrusion direction. After aging treatment, the elements of Zn, Ca, P and O presented a more homogeneous distribution. The compressive strengths of the β-Ca3(PO4)2/Mg-Zn composites were approximately double those of natural bone, and their densities and elastic moduli matched those of natural bone. The immersion tests and electrochemical tests revealed that the adding β-Ca3(PO4)2, hot extrusion and aging treatment could promote the formation of protective corrosion product layer on the sample surface in Ringers solution, which improved corrosion resistance of the β-Ca3(PO4)2/Mg-Zn composites. The XRD results indicated that the corrosion product layer contained Mg(OH)2, β-Ca3(PO4)2 and hydroxyapatite (HA). The cytotoxicity assessments showed the as-extruded β-Ca3(PO4)2/Mg-Zn composite aged for 72h was harmless to L-929 cells. These results suggested that the β-Ca3(PO4)2/Mg-Zn composites prepared by powder metallurgy were promising to be used for bone tissue engineering.

Tailoring properties of porous Poly (vinylidene fluoride) scaffold through nano-sized 58s bioactive glass.

Abstract The biological properties of porous poly (vinylidene fluoride) (PVDF) scaffolds fabricated by selective laser sintering were tailored through nano-sized 58s bioactive glass. The results showed that 58s bioactive glass distributed evenly in the PVDF matrix. There were some exposed particles on the surface which provided attachment sites for biological response. It was confirmed that the scaffolds had highly bioactivity by the formation of bone-like apatite in simulated body fluid. And the bone-like apatite became dense with the increase in 58s bioactive glass and culture time. Moreover, the scaffolds were suitable for cell adhesion and proliferation compared with the PVDF scaffolds without 58s bioactive glass. The research showed that the PVDF/58s bioactive glass scaffolds had latent application in bone tissue engineering.

Synergistic Effect of Carbon Nanotubes and Graphene on Diopside Scaffolds

A synergetic effect between carbon nanotubes (CNTs) and graphene on diopside (Di) scaffolds was demonstrated. 3D network architecture in the matrix was formed through the 1D CNTs inlaid among the 2D graphene platelets (GNPs). The mechanical properties of the CNTs/GNPs/Di scaffolds were significantly improved compared with the CNTs/Di scaffolds and GNPs/Di scaffolds. In addition, the scaffolds exhibited excellent apatite-forming ability, a modest degradation rate, and stable mechanical properties in simulated body fluid (SBF). Moreover, cell culturing tests indicated that the scaffolds supported the cells attachment and proliferation. Taken together, the CNTs/GNPs/Di scaffolds offered great potential for bone tissue engineering.