Binglin He

A preliminary in vitro study on the fabrication and tissue engineering applications of a novel chitosan bilayer material as a scaffold of human neofetal dermal fibroblasts.

The bilayer structure of chitosan film and sponge was designed as a scaffold of skin tissue engineering and a dermis substitute. It was processed successively via the formation of a dense chitosan film by casting method and a porous chitosan sponge by lyophilization. The dry thickness of the film layer was 19.6 microm and that of the sponge layer was controlled at 60-80 microm. Porogens such as sodium chloride, glucose, and sucrose were used to create large pores of the chitosan sponge layer. Human neofetal dermal fibroblasts were seeded in the chitosan sponge layer and cultured for 4 weeks. It was found that the cells could grow and proliferate well in an extended shape on the flat bottom of large pores with 15-100 microm width and in spherical form on the rough pore walls or at the edges of micropores less than 5 microm. Fibroblasts after the culture could bind tightly with the sponge layer via newly formed extracellular matrices to give a living cell-matrix-chitosan composite. The bilayer chitosan material remained stable in shape and size during the cell culture. The results suggested that the bilayer chitosan material would be an alternative of collagen materials which was obviously contracted during cell culture.

Structural characterization of phosphorylated chitosan and their applications as effective additives of calcium phosphate cements.

Chitosan was phosphorylated by P2O5 in methanesulfonic acid and the product as water-soluble phosphorylated chitosan (P-chitosans) was then characterized by phosphorus elemental analysis, IR and 31P-NMR spectroscopy. Two calcium phosphate cement (CPC) systems, i.e. (1) monocalcium phosphate monohydrate (MCPM) and calcium oxide (CaO) in 1 M phosphate buffer (pH = 7.4) and (2) dicalcium phosphate dihydrate (DCPD) and calcium hydroxide [Ca(OH)2] in 1 M Na2HPO4 solution, were chosen to improve their mechanical properties by the addition of water-soluble P-chitosans with various values for molecular weight, degree of deacetylation (DD) and degree of substitution (DS). The results show that the compressive strength (CS) and Youngs modulus of both CPC formulations after setting were obviously increased and setting time was slightly prolonged by adding water-soluble P-chitosan to the liquid phases. When a suitable amount of P-chitosan was used, two improved CPC formulations were obtained with much better mechanical properties while the setting times were not longer than 15 min. The enhancement of compressive strength was due to high Ca2+-binding ability of phosphorylated chitosan, which could tightly bind the newly formed hydroxyapatite (HA) particles together by polymeric chains. It was noted that excessive addition of P-chitosan would lead to slow setting or no setting at all. The hardened CPC samples containing P-chitosan were characterized via X-ray diffraction spectra and scanning electron microscopy. Their leaching experiment was also carried out. The results indicated that P-chitosan-forced calcium phosphate cements have some good characteristics for clinical applications.

Bone repair in radii and tibias of rabbits with phosphorylated chitosan reinforced calcium phosphate cements

Biocompatibility of two calcium phosphate cements (CPCs), reinforced with phosphorylated chitosan (P-chitosan), was investigated in rabbits in present study. The two CPCs are monocalcium phosphate monohydrate (MPCM) with calcium oxide (CaO) in 1 M phosphate buffer (i.e. MCPM/CaO/1 M phosphate buffer cement, CPC-I) and dicalcium phosphate dihydrate (DCPD) with calcium hydroxide [Ca(OH)2] in 1 M Na2HPO4 solution (i.e. DCPD/Ca(OH)2/1 M Na2HPO4 cement, CPC-II). Different amount of P-chitosan was added to the liquid phase before the power phase was mixed with the liquid phase. The MCPM/CaO/1 M phosphate buffer/P-chitosan cements (P-CPC-I) with neutral pH were filled into the holey defects of rabbit tibias. While the DCPD/Ca(OH)2/1 M Na2HPO4/P-chitosan cements (P-CPC-II) shaped as prehardened cylinders were implanted into rabbit radial defects. After operation, the two serial groups and CPC-II controls were observed for 1, 4, 12 and 22 weeks, respectively. Histological and histomorphological studies proved that P-chitosan containing cements are biocompatible, bioabsorbable and osteoinductive. The biodegradation rate has a negative relationship with the P-chitosan content. Progressive substitution took place at the interface of implants and host bones. No adverse effects were found in tissues around the bone defects. Thus, they could be used as bone substitutes in clinic.

Synthesis of bifunctional polymeric adsorbent and its application in purification of stevia glycosides

Abstract Polymeric adsorbents with both functions of adsorption and decolorization were synthesized by introducing quaternary ammonium groups (e.g. –N+(CH3)3 groups) into conventional resinic adsorbent used to adsorb stevia glycosides in production. The relation between the adsorption capacity of the bifunctional adsorbents for stevia glycosides and the structure of adsorbents, and that between the decolorization efficiency and the structure were investigated. The results revealed that the adsorption capacity for stevia glycosides decreased somewhat as the increase of the content of quaternary ammonium groups in the adsorbent, while the decolorization efficiency increased. Adsorbents containing about 0.6–0.8 mmol/g of –N+(CH3)3 groups showed both high adsorption capacity and high decolorization efficiency, and showed adsorptive selectivity for the small-sized components of stevia glycosides. Mechanism of adsorption and decolorization was also studied, and revealed that adsorption of stevia glycosides was based on hydrophobic interactions, but decolorization was based on both ion exchange and hydrophobic interactions. Introduction of –N+(CH3)3 groups into polymeric adsorbent also changed the adsorption selectivity for various stevia glycosides, and thus the bifunctional adsorbent could be used to prepare stevia glycosides with high content of rebaudioside A.

Synthesis of the adsorbent based on macroporous copolymer MA–DVB beads and its application in purification for the extracts from Ginkgo biloba leaves

The macroporous polymethacrylate beads were synthesized via suspension polymerization of methacrylate and divinylbenzene as crosslinker. Thus, a kind of adsorbent with high selectivity for ginkgo flavonol glycosides and terpene lactones was obtained. The relationship between the structure of the adsorbents and their adsorption properties was investigated in detail. The results show that the adsorbent with appropriate surface chemistries would be favorable to the adsorption for flavonol glycosides and terpene lactones, while relative smooth surface takes an important role in selectively adsorbing ginkgolides. Extracts of ginkgo leaves with more than 30% w/w flavonol glycoside and 8% w/w terpene lactones were prepared by using this kind of adsorbent as purification material.

A new type of ALSS — the preparation of crosslinked chitosan resins and its adsorption properties for bilirubin

With chitosan as a raw material, a new type of ALSS-CHP was prepared by the reaction of glutaric dialdehyde with chitosan. This type of resin has high adsorption capacity for bilirubin and good blood compatibility. The adsorption capacity was related to the degree of crosslinking of beads; phosphate buffer concentration; bilirubin concentration; pH value; BSA concentration and the size of resins.

Synthesis of gelatin–PVA adsorbent and its application in the separation of ginkgo flavonol glycosides and terpene lactones

Abstract Spherical adsorbents derived from the glutaraldehyde cross-linked hybrid of gelatin and polyvinyl alcohol (PVA) were synthesized, and their adsorption selectivity for ginkgo flavonol glycosides and terpene lactones was also investigated in detail. An adsorbent with an appropriate gelatin content can selectively adsorb flavonol glycosides with a high adsorption capacity based mainly on hydrogen bond interactions, while showing only a fairly low adsorption capacity for terpene lactones. A much higher adsorption affinity of flavonol glycosides than that of terpene was calculated from the adsorption isotherms. Thus, a simple preparative separation procedure for ginkgo flavonol glycosides and terpene lactones from a ginkgo leaf was established. An enriched extract containing flavonol glycosides of up to 60% and terpene lactones as low as 0.2% and an extract with a terpene lactones content up to 30% was prepared by this method, respectively.

Adsorption of bilirubin on the polymeric β-cyclodextrin supported by partially aminated polyacrylamide gel

Abstract A β-cyclodextrin resin supported by partially aminated polyacrylamide was synthesized from porous polyacrylamide. The adsorption of bilirubin on the polymeric β-cyclodextrin was investigated in 0.01 M phosphate buffer (pH = 7.4) at 37°C in different conditions with various temperature, pH value, bilirubin concentration and ionic strength, etc. The results indicated that the polymeric β-cyclodextrin was a good adsorbent for unconjugated bilirubin with high capacity.

The preparation of immunoadsorbents and their adsorption properties for anti-DNA antibodies in SLE serum

By using the hydroxyethyl crosslinked chitosan beads as the support, a novel immunoadsorbent was prepared by conjugating DNA onto the beads via the CNBr activation. The influence of conditions on the immobilization capacity of DNA was studied in detail. The adsorption experiments were performed by adding the immunoadsorbents to the SLE serum. The results showed that this type of immunoadsorbent could cut down the anti-DNA antibody levels by 65.33% at most in serum. Because the chitosan has good blood compatibility, this type of immunoadsorbent is hopeful for the treatment of SLE by hemoperfusion in the future.

Initial copolymer concentration influence on self-assembly of PS38-b-P(AA190-co-MA20) in water

The self-assembly of polystyrene-b-poly(acrylic acid-co-methyl acrylate) [PS38-b-P(AA190-co-MA20)] in water was studied. The initial block copolymer concentration greatly influences the morphologies of the resulting aggregates. The morphology of the resulting micelles changes from core–shell spheres with diameter 60 nm to 60–130 nm near-spherical aggregates, and further to 70 nm hollow aggregates, when the initial polymer concentration ranges from 0.20 to 0.50 mg mL−1 and further to 2.0 mg mL−1. The structure of the core–shell spheres and hollow aggregates is further characterized by light scattering. It is found that the core–shell micelles and the hollow aggregates are kinetically frozen in water; the aggregation number of polymer chains Nagg and molecular weight MW of the core–shell micelles and hollow aggregates are relatively large and the solubility of the two morphological micelles in water is poor; the structure of the core–shell spheres is incompact and the hollow aggregates is porous.