Papers by Author: Chang Ren Zhou

Abstract: Firstly, Magnesium oxide (MgO) whiskers were prepared by calcination of magnesium carbonate (MgCO₃₎ whiskers which were obtained by solution method. Then, surface-grafted MgO whiskers with poly (L-lactide) were synthesized by bulk ring-opening polymerization of L-lactide onto the surface of MgO whiskers. The MgO whiskers and surface-grafted MgO whiskers were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), x-ray diffraction (XRD) and fourier transformation infrared (FTIR). Results showed that MgO whiskers diameter in the range of 0.02-0.5μm, the length is between 10-80μm and well dispersed. A new characteristic stretching vibration absorption peak of C=O apppeared in the IR spectrum of the surface-grafted MgO whiskers, which suggested that poly (L-lactide) chains were successfully grafted on the surface of MgO whiskers.

Abstract: To mimic the alveolar bone and periodontal ligament interface, a chitosan(CS for short) composite polysaccharide scaffold was fabricated which was cross-linked with sodium alginate(SA for short). The conditions of physical crosslinking in the scaffolds were discussed. By characterization after biomineralization, it turns out that pH=5.0 and 40min crosslinking time can make for crosslinking. Better crosslinking makes the material more antiswelling and give more compressive strength. In the other hand, the biomineralization can improve the physical properties of the material. We hope that after further research it can come to a scaffold material with good properties.

Abstract: The prevention of undesired abdominal wall adhesion after surgery was investigated using asymmetric polysaccharide composite membranes as physical barriers. The hyaluronate (HA) and chitosan (CS) based asymmetric composite membranes were prepared with one smooth surface to inhibit fibroblasts and one porous surface to improve the tissue cells. With adaption of the reaction temperature, pH and component ratios, a series crosslinked membranes were processed with different appearance, mechanical strength and swelling ratios. Cell culture results showed the fibroblasts were inhibited on the composite membranes with comparison of that on petri dish. The osteoblasts proliferated obviously on the porous surface. The composite membranes resulted in less post-operative adhesion of the peritoneum and cecum than shown by non-treated rats without physical barriers, which could be used as a physical barrier to prevent abdominal post-operative adhesion during healing.

Abstract: Firstly, toluenesulfonyl cholesterol was synthesized by the reaction of cholesterol and p-toluenesulfonyl chloride, and then reacted with sodium azide to obtain azido-cholesterol. Secondly, propargyl was introduced into the terminal groups of polyethylene glycol (PEG) by the reaction of PEG and bromine propargyl. Lastly, cholesterol-(1,2,3-triazole)-PEG oligomer was prepared by the reaction of the azido-cholesterol and propargyl-PEG via click chemistry using CuSO4.5H2O as a catalyst. The structures of the products were characterized by the FTIR and 1H NMR analysis.

Abstract: Halloysite nanotubes (HNTs) surface-grafting poly(D,L-lactide) (g-HNTs) were synthesized by bulk ring-opening polymerization of D,L-lactide using stannous octoate as catalyst and HNTs as co-initiator. Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and zeta potential measurement were employed to elucidate the structure and properties of HNTs before and after grafting with D,L-lactide. FTIR spectrum certified the existence of poly(D,L-lactide) chains on the surface of g-HNTs. The amount of surface-grafted poly(D,L-lactide) measured by TGA was 4.6% in weight. The grafted poly(D,L-lactide) chains on the surfaces of HNTs can relieve the clustering effect of HNTs to some extents.

Abstract: Poly(D,L-lactide) (PDLLA) was synthesized firstly by the ring-opening polymerization of D,L-lactide using tin(II) 2-ethylhexanoate as catalyst in supercritical carbon dioxide (scCO₂). Then, PDLLA porous scaffolds were prepared in situ by scCO₂ extraction/pore forming technologies. The structure and the molecular weight of PDLLA were characterized by FT-IR, ¹H NMR and GPC respectively. The porous structure morphology of the prepared scaffolds was observed by SEM. Results showed that PDLLA was synthesised successfully in scCO₂ fluid, and the molecular weight and yield of PDLLA were affected by reaction time, temperature and the concentration of catalyst. The best polymerization conditions were obtained as follows: reaction time of 48 h, temperature of 100°C and the concentration of catalyst of 0.1%. SEM results revealed that uniformly distributed and highly interconnected pore structures with a unique long gully type microstructure were formed in the PDLLA scaffolds.

Abstract: For successful reconstruction of skeletal defects, a range of materials including ceramics, polymers and their composites have been developed. The goal of our work is to prepare mineralized PCL/gelatin composite scaffolds in a double diffusion system as implants for bone tissue engineering application. Fibrous PCL/gelatin scaffold fabricated via electrospinning followed by immersing into disodium-β-glycerophosphate(β-GP) (10 mg/ml) for 12h were used as substrates for calcium phosphate (CaP) mineralization. The precipitation reaction was biomimetically carried out in a double diffusion system for a week. The CaP minerals precipitated on the scaffold were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and high-resolution transmission electron microscopy. The results show that apatite aggregates are combination of HAP, DCPD and ACP. β-GP can effectively promote the formation of CaP crystals. The composite scaffold fabricated in this paper hold promise for use in bone tissue engineering.

Abstract: Stable water dispersions of single wall carbon nanotubes (SWCNTs) have important implications for their applications in biomedical and composites field. In this work, a water-soluble optical brightener bearing benzene ring and sodium sulfonate groups was employed as surfactant for SWCNTs in water. The surfactant molecules were absorbed on graphene nanotube surfaces via π-π interaction, Van Der Waals interaction and electrostatic interactions in water under ultrasonic treatment. The functionalized carbon nanotubes were stably dispersed in water for several months without sedimentation. The carbon nanotubes/organic conjugated molecules nanohybrids have potential application in nanocomposites, biomedical engineering, and photovoltaic devices.

Abstract: The biomineral-binding alendronate-chitosan conjugate (Scheme 1) was developed as a novel drug delivery system. Alendronate was conjugated to the hydroxyl groups of chitosan, thereby maintaining the amino groups of chitosan intact. By means of FT-IR and ¹H NMR, the characterization was conducted to confirm the successful synthesis of alendronate-chitosan conjugate.

Abstract: Solid freeform fabrication, known as rapid prototyping (RP) technology allows in designing the scaffold with pre-defined and controlled external and internal architecture.In this study we produce scaffolds with network of chitosan fibrils that mimic the extracellular matrix produced by the cells. These network scaffolds also consisting of nanoparticles of hydroxyapatite (HA) for stabilisation of scaffolds are characterised by environmental scanning electron microscopy and mechanical properties. ESEM showed that the scaffolds possess macropore (300µm), micropore and fibre network structure. The compressive strength and elastic modulus (E) for the scaffolds are 0.54± 0.02 MPa and 6.13± 0.60 MPa, respectively, which are increasing obviously. The biocompatibility of the woodpile-network scaffolds was investigated with osteoblastic cells. The result showed the distribution and proliferation of osteoblast orients along the chtosan fibre network, preferentially. After 4 weeks of culture, macropore channels are covered by cells in large part,while the areas without chitosan fibre network are covered rarely. The properties of these scaffolds indicate that they can be used for bone tissue engineering applications.