Papers by Author: Guo Ping Chen

Abstract: This paper presents a study on the dual-coupling characteristics between elastic plate and acoustic cavity. Modal superposition method was employed to analyze sound transmission in the plate-cavity-plate system and cavity-plate-cavity system. Impedance and mobility methods were also adopted which were easy to investigate the characteristics between the structural and acoustic systems. The expression of sound transmission between plate-cavity-plate system and cavity-plate-cavity system were given.

Abstract: The adsorption properties of metal ions containing hydroxyapatite (Ca10(PO4)6(OH)2, HAp) were elucidated for the development of protein drug carrier. As-prepared metal ion containing HAp nanocrystal showed plate-like morphology with 10-20nm in length and 5-10nm in width. The metal ion containing HAp microparticles had higher specific surface area than the HAp microparticle. The adsorption amount per unit area of HAp showed higher than those of metal ion containing HAp. The adsorption behavior followed the Langmuir curves for each protein, indicating the monolayer adsorption. The loaded amount of proteins could be one of the most important properties for the application of drug delivery carrier.

Abstract: Linear and Star-shaped PCL-b-PEG copolymers were synthesized through a two step process, including the first step to synthesize the star-shaped PCL through ring-opening polymerization of Γ-caprolactone initiated from multi-functional alcohol under the existence of tin(II) ethylhexanoate [Sn(Oct)2] catalyst, and the following step to couple the obtained star-shaped PCL with PEG segments using bi-functional linker. The structure of the polymers was confirmed by IR, NMR, GPC, et al. The aggregation behaviors of the star-shape copolymers were compared with that of the linear block copolymer with corresponding molecular weight of each arm, and the influences of structure factors were discussed.

Abstract: Time-controlled releases of proteins from hydroxyapatite/chondroitin sulfate (HAp/ChS) spherical microparticles were achieved by the addition of zinc cation into the mixture solutions of HAp/ChS and protein as a novel formulation. The initial bursts of proteins, such as cytochrome c and bovine serum albumin, were apparently suppressed by the amount of zinc cation, which could be attributed to the formation of coordinate bonds of zinc cation among proteins and/or ChS moleculars. The increase of molecular lengths of ChS chains decreased the adsorbed amount of proteins, which did not apparently affected to the release of proteins.

Abstract: Control of protein release without the initial burst from zinc containing hydroxyapatite porous microparticles (Zn-HAp) was investigated with a novel formulation method. The formulation method was a coat of polyL(L-lactide; PLA) on the microparticle with nano-thickness, which obviously suppressed the initial burst of protein release compared with the microparticles without the formulation, the coat of PLA. The HAp/PLA microparticle with 1-20μm of the size distribution was available for the drug delivery carrier of proteins without the degradation.

Abstract: In this study, three kinds of photo-reactive polymers, namely positively charged azidophenyl-derived polyallylamine (AzPhPAAm), negatively charged azidophenyl-derived poly(acrylic acid) (AzPhPAAc) and neutral azidophenyl-derived poly(ethylene glycol) (AzPhPEG), were synthesized by introduction of photo-reactive group (-N3) into polyallylamine, poly(acrylic acid) and poly(ethylene glycol), respectively. The structure of the azidophenyl-derived polymers was confirmed by 1H-NMR measurement. All of the photo-reactive polymers can be pattern-grafted on the surface of cells culture plate, which was confirmed by the optical microscopy observation. The contact angle decreased after surface modification by the photo-reactive polymers. Human mesenchymal stem cells (MSC) cultured on the modified surfaces showed different morphology. The cells adhered and spread more on the PAAm- and PAAc-grafted surfaces than on the PEG-grafted surface. The pellets formed on PAAm- and PEG-grafted surfaces in condrogenic differentiation medium were positively stained by safranin O/ fast green. But the pellet formed on PAAc-grafted surface did not show obviously positive staining for safranin O/ fast green. These results indicate that the PAAm- and PEG-grafted surfaces promoted chondrogenic differentiation of MSC.

Abstract: A novel collagen sponge that can protect cell leakage during cell seeding was developed by wrapping all the surfaces except the upside of a collagen sponge with membrane that has pores smaller than cell. The collagen sponge was used for three-dimensional culture of human bone marrow-derived mesenchymal stem cells (MSCs). The cells adhered to the collagen, and proliferated to fill the spaces in the sponge. The cell seeding efficiency was higher than 95%. The MSCs cultured in the collagen sponge in the chondrogenic induction medium supplemented with TGF-β3 and BMP6 expressed genes encoding type II collagen, SOX9 and aggrecan. HE staining indicated the round morphology of differentiated cells and the extracelluler matrices were positively stained by safranin O and toluidine blue. Type II collagen and cartilage proteoglycan were detected by immunostaining with anti-type II collagen and anti-cartilage proteoglycan. These results suggest the chondrogenic differentiation of MSCs. The collagen sponge facilitated cell seeding and chondrogenic differentiation of MSCs, and will be useful for cartilage tissue engineering.

Abstract: Three-dimensional biodegradable porous scaffolds play an important role in tissue engineering as temporary templates for transplanted cells to guide the formation of the new organs. Two kinds of novel biodegradable porous scaffolds for tissue engineering have been developed by our group by hybridizing synthetic poly(α-hydroxy acids) with naturally derived collagen. One is their hybrid sponge prepared by introducing collagen microsponges in the pores of poly(α-hydroxy acids) sponge. The other one is their hybrid mesh prepared by forming collagen microsponges in the interstices of poly(α-hydroxy acids) mesh. The hybrid scaffolds were used for three-dimensional culture of fibroblast, tenocytes, chondrocytes and mesenchymal stem cells for tissue engineering of skin, ligament, cartilage and osteochondral tissue. These cells adhered and spread well in the hybrid scaffolds, proliferated, secreted extracellular matrices and formed the respective tissues. The synthetic polymer sponge, or mesh serving as a skeleton, reinforced the hybrid scaffolds and resulted in easy handling, while the collagen microsponges provided the hybrid sacffolds with a microporous structure and hydrophilicity, and therefore, easy cell seeding. The hybrid scaffolds will be useful for tissue engineering.

Abstract: Hydroxyapatite/chondroitin sulfate (HAp/ChS) microparticles with the perfectly spherical shape and the averaged particle sizes of 4.1, 7.8, 19.9 and 29.4 µm were fabricated by a spray dry method under the different atomizing pressures and the concentrations of suspensions. The contents of ChS in the microparticles were varied at 1.49, 3.18, 7.82, 14.2 wt%, and the ChS elution rate in distilled water from the microparticles was increased with the increase of ChS contents. The adsorption isotherms of cytochrome C on the microparticles in 1/10 diluted phosphate buffer saline (PBS) were followed to the Langmuir’s equation regardless of the change of ChS contents, while those of catalase were not followed. The HAp/ChS microparticles can adsorb greater amount of cytochrome C than pure HAp microparticles, but less amount of catalase than pure HAp. The electrostatic interaction between the proteins and ChS was of great importance in the adsorption properties.

Abstract: Hydroxyapatite (HAp) also shows the high absorption ability for proteins with low degradations. In this study, to modify the absorption ability and to obtain high surface area, metal ions (Zn, Mg, Fe) were introduced in preparing the HAp nanocrystals, and porous microparticles were subsequent fabricated by a spray drying method. HAp microparticles with Zn, Mg, Fe ions had a single phase of low crystalline HAp. The specific surface area of the HAp, Mg-HAp, Fe-HAp and Zn-HAp were 87, 150, 152, 167 m2/g, respectively. In the adsorption experiment of a lysozyme as a basic proteine, Zn-HAp showed the highest adsorption ability. On the other hand, the HAp microparticles witn metal ions showed higher adsorption ability for BSA as a acitic protein than pure HAp microparticles.