Ying Jun Wang

Modified PHBV scaffolds by in situ UV polymerization: structural characteristic, mechanical properties and bone mesenchymal stem cell compatibility.

An ideal scaffold provides an interface for cell adhesion and maintains enough biomechanical support during tissue regeneration. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) scaffolds with pore sizes ranging from 100 to 500 microm and porosity approximately 90% were prepared by the particulate-leaching method, and then modified by the introduction of polyacrylamide (PAM) on the inner surface of scaffolds using in situ UV polymerization, with the aim of enhancing the biological and mechanical properties of the PHBV scaffolds. The modified PHBV scaffolds had interconnected pores with porosity of 75.4-78.6% and pore sizes at peak volume from 20 to 50 microm. The compressive load and modulus were up to 62.45 N and 1.06 MPa, respectively. The water swelling percentage (WSP) of the modified PHBV scaffolds increased notably compared with that of the PHBV scaffolds, with the maximum WSP at 537%. Sheep bone mesenchymal stem cells (BMSC) were cultured on the PHBV and modified PHBV. The hydrophilic PAM chains did not influence BMSC viability or proliferation index, but the initial cell adhesion at 1h of culture was enhanced significantly. Framing PHBV scaffold along with gel-like PAM chains inside is a novel model of inner surface modification for PHBV scaffolds, which shows potential in tissue engineering applications.

Investigations on the formation mechanism of hydroxyapatite synthesized by the solvothermal method

In this paper, uniform hydroxyapatite (HA) nanowires of width 60 nm and length 1 µ ma re synthesized by solvothermal synthesis. The formation process of the nanowires has been elaborated from the structure within the reverse micelles b yt hetime-resolved fluorescence quenching technique. The results reveal that the formation of amorphous nuclear/surfactant complex and the electrostatic field within the reverse micelles maintain the unidirectional, irreversible fusion of reverse micelles, leading to the growth of nanowires in one direction. In the solvothermal synthesis, the pressure generated in the autoclave is estimated. The results suggest that the products are prepared under stable conditions without intense shearing stress where it is favourable for the formation of long and uniform HA nanowires.

Preparation and characterization of poly(vinyl alcohol)/hydroxylapatite hybrid hydrogels

Poly(vinyl alcohol)(PVA)/hydroxylapatite(HA) hybrid hydrogels used for bioactive artificial cartilage were prepared by compounding in situ with sol—gel synthesis of HA in PVA solution. To draw comparisons, both physical mixing and deposition in situ methods were also used to prepare hybrid hydrogels. The influence of contents and dispersed condition of HA in PVA matrixes on hydrogels mechanical strength were investigated and compared. The micromorphology and crystalline structure of HA were also observed by some analysis techniques. It was verified that the distinct conglomeration of HA particles in PVA matrixes were overcome using sol—gel in situ methods, and mechanical strength of PVA/HA hydrogels increased obviously compared to deposition in situ and physical mixing methods. HA particles being dispersed uniformly in PVA hydrogels prepared by sol—gel in situ compounding were of crystalline structure, which acted as a kind of heterogeneous nucleating agent improving the crystallization of PVA by depressing the dependence of the crystalline process on the temperature and external factors, hence raising the tensile strength of hybrid hydrogels.

Investigation on the Porous Biomaterial for Bone Reconstruction with Addition of Bio-Mimetic Nano-Sized Inorganic Particles

The spherical nano-sized bioactive particles in the system of CaO-P2O5-SiO2 were bio-mimetically synthesized using micro-emulsion method. The microstructures and properties of the bio- mimetic nano-materials were characterized using XRD, FTIR, SEM/EDAX and TEM techniques. It was indicated that the nano-particles possessed glassy structural characteristics. The porous composite for bone tissue reconstruction was prepared by compounding poly (hydroxybutyrate-2-co-2-hydroxyvalerate) (PHBV) and the nano-particles of bio-mimetic bioactive glasses (BMBG). Bone-like hydroxyl- carbonate-apatite (HCA) could formed on the surface of porous composite by immersing the composite in simulated body fluid (SBF) at 37°C for 8 hours. With increase of immersion time, the morphology of HCA changed from spherical into flake-like crystals. The study on cells attachment of the porous PHBV/BMBG composite proved that the material possessed satisfactory bioactivity, bio-mineralization function and cells biocompatibility.

Preparation of Bioactive Nanoparticles in the System CaO-P2O5-SiO2 Using Microemulsions

The bioactive nanoparticles in the system CaO-P2O5-SiO2 were synthesized via microemulsions method in this study. The structure and properties of the nanoparticles were investigated in details using XRD, TEM, FTIR, BET techniques. It was found that, in a stable phase W/O emulsions, the diameter of the nanoparticles were related to the molar ratio of water to surfactant (γ). Under the favorable conditions, i.e. γ=6, nano-sized spherical amorphous particles could be obtained with the average diameter of 25 nm. The microemulsions could be an alternative method to prepare bioactive nanoparticles for bone reparation and bone tissue engineering scaffolds.

Bioactive surface modification on amide-photografted poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Collagen was chemically immobilized on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films via hydrophilic polyacrylamide spacers, aiming to establish the bioactive surface and the inner surface models. The inner surface modified films presented higher wettability than the surface modified films. Wide-angle x-ray diffraction results showed that the d-spacing values of the inner surface model increased compared with those of the surface model, but there was no significant difference between the amide- and collagen-modified PHBV films. The peak melting temperatures of PHBV and the special endotherm around 70 °C were following the order: PHBV > amide-modified PHBV > collagen-modified PHBV. The weight loss of the collagen-modified PHBV (inner surface model) might involve hydrolyzation and mineralization during 360 days of incubation, with a maximum value of 18.24%, while PHBV films did not show significant weight loss. The pH value of the degradation fluids fluctuated in the range of 6.86-7.22, as the initial pH was recorded at 7.20. Based on the surface model, collagen-modified PHBV scaffolds were prepared, which enhanced chondrocyte adhesion and spread on the biomimetic surface. Two surface modification models might develop a protocol with a view to generating a biocompatible and biomechanical scaffold for use in meniscus regeneration.

Bone-Like Apatite Formation on Modified PCL Surfaces under Different Conditions

The PCL plates hydrolyzed by NaOH aqueous solutions and carboxylate groups were introduced onto the surfaces of specimen. Specimens were treated by CaCl2 and K2HPO4⋅3H2O under the normal-pressure condition and low-pressure of 103 Pa condition for 30min separately. Dense and uniform bone-like layers could be formed on the surface of specimens after mineralizing for less than 24h in simulated body fluids (SBF). The low-pressure condition could accelerate the formation of apatite layer.

Rheological Properties and Injectability of a Calcium Phosphate Bone Substitute Material

A calcium phosphate bone substitute material was prepared and its rheological behavior and injectability were studied in this work. The effects of temperature, L/P ratio and adjuvant on the rheological properties and injectability of the pastes were discussed. The results show that the calcium phosphate bone substitute material is injectable with good fluidity and is suitable for the clinical applications. The rheological behavior and injectability of the bone substitute material can be improved by adding adjuvants and optimizing L/P ratio.

Bioactive Hydroxyapatite/ Polyvinyl Alcohol Composite for Repair and Regeneration of Articular Cartilage

In this work, a new kind of bioactive PVA/HA hydrogels use as artificial cartilage were prepared by in situ sol-gel synthesis method. Simulated experiments were performed to evaluate and compare the bioactive ability and properties of the hydrogels in simulated body solution. PVA/HA Cartilage implants were developed and used to repair articular cartilage defect in rabbit knee. The macroscopic and histological observation of animal experiments displayed that the implanted hydrogels combined tightly to ambient tissues, and some bone-like tissue grew into the bottom of the implants from the base-bone to form more deep-set binding.

Microstructure and Properties of A Calcium Phosphate Cement Tissue Engineering Scaffold Modified with Collagen and Chitosan

In this study, an ACP-DCPD based Calcium phosphate cement (CPC) scaffold with a porosity of 88% was prepared by using Na3PO4 as a poregen and then modified by collagen and chitosan. The results showed that collagen and chitosan obviously increased the compressive strength. Cell culture showed that the cell can migrate, attach, proliferate and differentiate on the surface of the materials and the pores walls. This CPC scaffold modified with collagen or chitosan was a promising material to be used in bone tissue engineering.