Hong Xia

A three-dimensional porous hydroxyapatite nanocomposite scaffold with shape memory effect for bone tissue engineering

It is known that scaffold is a key factor in bone tissue engineering. The aim of this study was to improve the design of scaffold in order to achieve an effect of precisely matching the irregular boundaries of bone defects as well as facilitate clinical application. In this study, controllable three-dimensional porous shape memory polyurethane/nano-hydroxyapatite composite scaffolds were successfully fabricated. Detailed studies were performed to evaluate its structure, porosities, and mechanical properties, emphasizing the effect of different apertures of scaffolds on shape recovery behaviors and biological performance in vitro. Results showed its compression recovery ratios and shape recovery ratios of all scaffolds could reach more than 99 and 90%, respectively, which could let it more accurately match the irregular boundaries of bone defects. And also its cell proliferation ability was improved with the increase in the apertures. Thus, these scaffolds have potential applications for the bone tissue engineering.

The effect of hydroxyapatite nanoparticles on mechanical behavior and biological performance of porous shape memory polyurethane scaffolds

The scaffold which provides space for cell growth, proliferation, and differentiation, is a key factor in bone tissue engineering. However, improvements in scaffold design are needed to precisely match the irregular boundaries of bone defects as well as facilitate clinical application. In this study, controllable three-dimensional (3D) porous shape memory polyurethane/nano-hydroxyapatite (SMPU/nHAP) composite scaffold was successfully fabricated for bone defect reparation. Detailed studies were performed to evaluate its structure, apparent density, porosity, and mechanical properties, emphasizing the contribution of nHAP particles on shape recovery behaviors and biological performance in vitro. The effect of nHAP particles in porous SMPU/nHAP composite scaffold was found to enhance the compression resistance by 37%, shorten the compression recovery time by 41%, reduce the tensile resistance by 78%, reach the shape recovery ratio of 99%, and promote the cell proliferation by 13% after 7 days of culture. These results revealed that the 3D structure and aperture of as-prepared scaffold were controllable. And in minimally invasive surgery and bone repair surgery, this porous composite scaffold could significantly reduce the operative time and promote the bone cell growth. Therefore, this porous SMPU/nHAP composite scaffold design has potential applications for the bone tissue engineering.

Electrospinning, processing and characterization of polymer-based nano-composite fibers

Abstract: Electrospinning is a relatively simple and inexpensive method to produce fibers with diameters in the nanometer range. In recent years, many different kinds of polymer nanofibers have been fabricated by electrospinning technology, including nano-composite fibers. The challenges of developing multifunctional nano-composite fibers are reviewed in this chapter. CoFe 2 O 4 nanoparticles with a particle size of about 10–25xa0nm were synthesized using a simple hydrothermal process. CoFe 2 O 4 /PAN (polyacrylonitrile) nanofibers with various CoFe 2 O 4 loadings were prepared by electrospinning, and the fiber diameter was controlled to a distribution of between 200 and 400xa0nm. Then, PAN nano-composite fibers containing carbon nanotubes (CNTs) and CoFe 2 O 4 nanoparticles were fabricated by electrospinning. The presence of CoFe 2 O 4 nanoparticles and CNTs in the PAN matrix was confirmed by X-ray diffraction (XRD) patterns, Raman spectra, SEM, and TEM observation. As a multifunctional material, the nano-composite fibers achieved both EMI SE and magnetic performance for the developed PAN/CNT-CoFe 2 O 4 fibers. This performance can be accurately tailored by adjusting CoFe 2 O 4 nanoparticle loading.

A New Approach for Quantitative Evaluation of Ultrasonic Wave Attenuation in Composites

When ultrasonic waves propagate in composite materials, the propagation behaviors result from the combination effects of various factors, such as material anisotropy and viscoelastic property, internal microstructure and defects, incident wave characteristics and interface condition between composite components. It is essential to make it clear how these factors affect the ultrasonic wave propagation and attenuation characteristics, and how they mutually interact on each other. In the present paper, based on a newly developed time-domain finite element analysis code, PZflex, a unique approach for clarifying the detailed influence mechanism of aforementioned factors is proposed, in which each attenuation component can be extracted from the overall attenuation and analyzed respectively. By taking into consideration the interrelation between each individual attenuation component, the variation behaviors of each component and internal dynamic stress distribution against material anisotropy and matrix viscosity are separately and quantitatively evaluated. From the detailed analysis results of each attenuation component, the energy dissipation at interface is a major component in ultrasonic wave attenuation characteristics, which can provide a maximum contribution rate of 68.2xa0% to the overall attenuation, and each attenuation component is closely related to the material anisotropy and viscoelasticity. The results clarify the correlation between ultrasonic wave propagation characteristics and material viscoelastic properties, which will be useful in the further development of ultrasonic technology in defect detection.

Application of Electrospun Nanofibers in Electromagnetic Interference Shielding

The challenges of developing multifunctional nano-composite fibers are reviewed in this chapter. Nano-composite fibers made from polyacrylonitrile (PAN) or polyvinyl alcohol (PVA) containing the components, such as multiwalled CNTs (MWCNT), magnetic nanoparticles Fe3O4, and CoFe2O4, were fabricated by electrospinning technology. CoFe2O4/PAN nanofibers with various CoFe2O4 loadings were prepared, and the fiber diameter was controlled between 200 and 400 nm. For developed PAN nano-composite fibers containing CNTs and CoFe2O4 nanoparticles, the presence of CoFe2O4 nanoparticles and CNTs in the PAN matrix was confirmed by XRD patterns, Raman spectra, and SEM and TEM observations. The PVA-based nano-composite fibers with Fe3O4 or MWCNT were also fabricated. Polyacrylic acid (PAA) was used as a polymer surfactant to stabilize Fe3O4 NPs aqueous suspension and facilitate their dispersal in PVA solutions. PAA was also used as a cross-linking agent to enhance the water resistance of the magnetic composite nanofibers through heat treatment, which provides a simple and convenient process to prepare homogenous NPs/PVA composite system. Incorporating CNTs, Fe3O4, and CoFe2O4 nanoparticles, the results showed that the developed electrospun nanofibers were suitable for the applications in electromagnetic interference (EMI) shielding effectiveness (SE) field and their performance can be tailored by adjusting fillers loading.