Cheng-Dong Xiong

Chinese Academy of Sciences, Peping, Beijing, China

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Publications (16)35.48 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In order to expand the application of poly(p-dioxanone) or PPDO in biomedical area, a series of novel copolymers were synthesized successfully by one-step, melted copolymerization of p-dioxanone (PDO) and l-phenylalanine N-carboxyanhydride (l-Phe-NCA) monomers. With the in-feed molar ratio of l-Phe-NCA/PDO equal to 1/20, the conversions of the two kinds of monomers were calculated from 1H NMR. The average molecular weight and polydispersity of the copolymer increase with the increasing reaction time and catalyst concentration. However, the conversions of the two kinds of monomers did not change with the reaction conditions. A three-step mechanism is presented and proved by high resolution 1H NMR and IR spectrums.
    Chinese Chemical Letters 05/2013; 24(5):392–396. · 1.18 Impact Factor
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    ABSTRACT: A biodegradable and thermoplastic elastomer—poly(L-lactide-co-ε-caprolactone) (PLLCA)—was reinforced with 5, 10, 20, and 30wt% of CaCO3 whiskers. We assessed the influence of the CaCO3 whisker content on the mechanical and thermal properties of the PLLCA/CaCO3 whisker composites. Scanning electron microscopy (SEM) revealed that the CaCO3 whiskers were uniformly distributed in the composite matrices. The results of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) showed that the glass transition temperatures (T g) of the composites increased slightly with increasing CaCO3 whisker content. At low CaCO3 whisker contents, the tensile strengths of the composites increased sharply with increasing CaCO3 content, the Young’s moduli also increased, and the elongation at break values gradually decreased. Thermogravimetric analysis (TGA) showed that the CaCO3 whiskers can promote the thermal degradation of PLLCA. Shape memory test results indicated that an appropriate amount of CaCO3 whiskers can improve the shape memory properties of PLLCA. KeywordsParticle reinforcement–Mechanical properties–Thermal degradation–Shape memory properties
    Journal of Polymer Research 01/2011; 18(3):329-336. · 2.02 Impact Factor
  • Macromolecular Materials and Engineering 03/2010; 295(4):381 - 385. · 2.34 Impact Factor
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    ABSTRACT: A series of biodegradable polymers were prepared by solution coprecipitation of poly(para-dioxanone) (PPDO) and poly(d,l-lactide) (PDLLA) in various blend ratios. Samples were compression molded into bars using a platen vulcanizing press. The in vitro hydrolytic degradation of PPDO/PDLLA blends was studied by examining the changes in weight, water absorption, tensile strength, breaking elongation, thermal properties, and morphology of the blends in phosphate buffered saline (PBS; pH 7.44) at 37°C for 8 weeks. During the hydrolytic degradation, the weight loss and water absorption increased significantly for all samples, whereas the hydrolysis rate varied with the blend composition. The weight loss of PPDO/PDLLA 80/20, which showed the smallest degradation rate, was lower than that of pure PPDO for almost all of the hydrolytic degradation period. The results showed that the blend composition played an important role in determining the degradation behaviors of blends.
    Materials Chemistry and Physics - MATER CHEM PHYS. 01/2010; 122(1):79-86.
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    ABSTRACT: Considering the mechanical properties and shape-memory properties, we developed a novel biodegradable compound shape-memory-polymer blend composed of poly (l-lactide-co-ε-caprolactone) (PLLCA) and poly (l-lactide-co-glycolide) (PLLGA). In comparison with most reported shape-memory blends, our blend showed outstanding shape-memory properties at higher stationary-phase concentrations (more than 50% w/w). The results of scanning electron microscopy (SEM) demonstrated the immiscibility between PLLCA and PLLGA. The tensile test results revealed that blends with different PLLGA concentrations showed different mechanical properties. The results of the shape-memory tests suggested that the blends showed improved recovery and fixing performances with an increase in the PLLGA content, especially at PLLGA concentrations greater than 50 wt.%.
    Materials Letters. 01/2010;
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    ABSTRACT: The most commonly used anti-adhesion device for separation and isolation of wounded tissues after surgery is the polymeric membrane. In this study, a new anti-adhesion membrane from polylactide-polyethylene glycol tri-block copolymer (PELA) has been synthesized. The synthesized copolymers were characterized by gel permeation chromatography and (1)H nuclear magnetic resonance spectroscopy. PELA membrane was prepared by electrospun. The prepared copolymer membranes were more flexible than the control poly-d-l-lactic acid (PDLLA) membrane, as investigated by the measurements of glass transition temperature. Its biocompatibility and anti-adhesion capabilities were also evaluated. In vitro cell adhesions on the PELA copolymer membrane and PDLLA membrane were compared by the culture of mouse fibroblasts L929 on the surfaces. For in vivo evaluation of tissue anti-adhesion potential, the PDLLA and PELA copolymer membranes were implanted between cecum and peritoneal wall defects of rats and their tissue adhesion extents were compared. It was observed that the PELA copolymer membrane was very effective in preventing cell or tissue adhesion on the membrane surface, probably owing to the effects of hydrophilic polyethylene glycol.
    Acta biomaterialia 05/2009; 5(7):2467-74. · 5.09 Impact Factor
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    ABSTRACT: The aim of this study was to investigate the potential of poly(ethylene glycol-co-lactide) (PELA tri-block with a segmental sequence of PLA-PEG-PLA) electrospun membranes as drug-delivery vehicles using metronidazole as a model drug. PELA membranes with smooth surfaces and no bead defects were electrospun from polymer solutions containing 20% (w/v) PELA in 8:2 N,N-dimethyl formamide (DMF)/acetone. The morphology of the drug-loaded electrospun membranes was influenced by electrospinning parameters such as the flow rate and voltages during preparation. Metronidazole could be released from the electrospun membranes and was characterized by an initial burst effect. Higher voltages led to faster release rates, while an increase in the flow rate decreased the drug release. The incorporation of metronidazole into the electrospun membranes decreased their surface hydrophilicity. The amount of drug released from the electrospun membranes was effective in inhibiting microbial growth. Cell adhesion on the PELA membranes with or without drug was less than that on the homo-polymeric PDLLA membranes. Proliferation of L929 mouse fibroblasts on the PELA membranes was observed. This study confirms the potential of metronidazole-loaded PELA biodegradable electrospun membranes for optimizing the clinical therapy of post-surgical adhesions and infections.
    Journal of Biomaterials Science Polymer Edition 02/2009; 20(9):1321-34. · 1.70 Impact Factor
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    ABSTRACT: BACKGROUND: Poly(para‐dioxanone) (PPDO) is a biodegradable polyester with excellent biodegradability, bioabsorbability, biocompatibility and mechanical flexibility. However, its high cost and relatively fast degradation rate have hindered the development of commercial applications. Blending with other polymers is a simple and convenient way of modifying the properties of aliphatic polyesters. Poly(D,L‐lactide) (PDLLA) is another polyester that has been extensively studied for biomedical applications due to its biocompatibility and suitable degradation rate. However, to our knowledge, blends of PPDO/PDLLA have not been reported in the literature.RESULTS: A series of biodegradable polymers were blended by solution co‐precipitation of PPDO and PDLLA in various blend ratios. The miscibility, morphology and thermal properties of the materials were investigated. DSC curves for all blends revealed two discrete glass transition temperatures which matched the values for pure PPDO and PDLLA. SEM images of fracture surfaces displayed evidence of phase separation consistent with the DSC results. The contact angles increased with the addition of PDLLA.CONCLUSION: PPDO/PDLLA blends exhibit two distinct glass transition temperatures that remain nearly constant and correspond to the glass transition temperatures of the homopolymers for all blend compositions, indicating that blends of PPDO and PDLLA are immiscible. Images of the surface obtained using SEM were also suggestive of a two‐phase material. The crystallinity of the PPDO phase in the blends was affected by the PDLLA content. The mechanical properties of the blends changed dramatically with composition. Adding PDLLA makes the blends less hydrophilic than PPDO. Copyright © 2008 Society of Chemical Industry
    Polymer International 01/2009; 58(2):183-189. · 2.13 Impact Factor
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    ABSTRACT: The in vitro hydrolytic degradation of high molecular weight poly (para-dioxanone) was studied by examining the changes of weight retention, water absorption, pH value, tensile strength, break elongation, thermal properties, and morphology of high molecular weight PPDO in phosphate buffered saline (PBS) (pH7.44) at 37°C for 8weeks. During the degradation, all samples’ weight retention decreased and water absorption increased significantly, whereas hydrolysis rate of PPDO bars varied with molecular weight. Compared with lower molecular weight samples, higher molecular weight PPDO samples exhibited higher hydrolysis rate. The samples’ glass transition temperature (Tg) decreased notably, while the degrees of crystallinity (Dc) increased. The samples almost totally lost their tensile strengths and breaking elongation after 4weeks of degradation. The results suggested that the stability of PPDO in vitro hydrolytic degradation increased with the increase of molecular weight.
    Journal of Polymer Research 01/2009; 16(5):471-480. · 2.02 Impact Factor
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    ABSTRACT: To improve the hydrophilicity, pliability, and egradability of some biodegradable polymers such as polylactide (PLA), a triblock copolymer, and poly(ethylene glycol-co-lactide) (PELA) has been electrospun into fibrous membranes in the fiber sizes of 7.5 microm to 250 nm. The relationship between electrospinning parameters (such as voltage, concentration, and feeding rate) and the fiber diameters has been investigated. The characterizations for the structure and morphology of electrospun membranes were carried out using differential scanning calorimetry (DSC), (1)H NMR, and scanning electron microscopy (SEM). The hydrophilicity of the membrane was determined by contact angle measurements in bi-distilled water, and it was shown that the hydrophilicity of the copolymer could be adjusted by the content of the poly (ethylene glycol) (PEG) segment in the copolymer. The results of in vitro degradation study showed that the submicrostructure of the fibrous membrane and the incorporation of hydrophilic PEG into PLA block could accelerate the degradation of the membrane in regards to the changes of inherent viscosity, tensile strength, and weight loss.
    Journal of Biomedical Materials Research Part A 10/2007; 82(3):680-8. · 2.83 Impact Factor
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    ABSTRACT: Carboxymethyl konjac glucomannan-chitosan (CKGM-CS) nanoparticles, which are well dispersed and stable in aqueous solution, were spontaneously prepared under very mild conditions via polyelectrolyte complexation. The physicochemical properties of the nanoparticles were identified by Zetasizer 3000 and Fourier transform infrared. It was found that at various CKGM and CS concentrations the particles ranged in size from approximately 50 to 1200 nm, and the zeta potential from 15 to 45 mV. By changing pH value of the medium and increasing the concentration of salt, the mean size of the particles increased and the zeta potential decreased. Also, investigations on the encapsulation efficiency of the bovine serum albumin loaded CKGM-CS nanoparticles were also undertaken. This nanoparticulate system driven by complex formation shows potential as an advanced drug delivery system for water-soluble drugs.
    Biopolymers 06/2005; 78(1):1-8. · 2.88 Impact Factor
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    ABSTRACT: Carboxymethyl konjac glucomannan-chitosan (CKGM-CS) nanoparticles were spontaneously prepared under very mild conditions via polyelectrolyte complexation. Bovine serum albumin (BSA), as a model protein drug, was incorporated into the CKGM-CS nanoparticles. The physicochemical properties of the BSA-loaded nanoparticles were identified by Zetasizer 3000 and FTIR spectrophotometry. Their sizes were from 330 nm to 900 nm; zeta potentials were positive according to varies CKGM/CS ratios. The encapsulation efficiency was up 20%. The release behavior in vitro of BSA from the nanoparticles was also investigated. We could find that the BSA release from the CKGM-CS nanoparticles is much more influenced by the CS coating layer than by the CKGM inner structure. And the CKGM-CS matrices not only exhibited pH-responsive properties, but ionic strength-sensitive properties. These systems may present a potential for pulsatile protein drug delivery.
    Journal of Biomedical Materials Research Part B Applied Biomaterials 03/2005; 72(2):299-304. · 2.31 Impact Factor
  • Macromolecular Rapid Communications 04/2004; 25(9):954 - 958. · 4.93 Impact Factor
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    ABSTRACT: Poly(etheretherketone) (PEEK) is a rigid semicrystalline polymer that exhibits excellent mechanical properties and bone-like stiffness and is widely used in biomaterials. However, the development of PEEK-based bioinert materials has been impeded because PEEK lacks bioactivity. In this study, a series of PEEK/carbon nanotubes (CNTs)/bioactive glass (BG) ternary nanocomposites were produced using injection molding. BG was added to the composites in order to improve the bioactivity of the PEEK, and a novel method of adsorption and co-precipitation was used to add the CNTs to the composites in order to compensate for the deterioration in the mechanical properties of the PEEK caused by the addition of the BG. The microstructures of the composites were investigated using scanning electron microscopy (SEM), and the SEM images revealed that this method permits the uniform dispersion of the CNTs throughout the PEEK matrix. Further, the mechanical properties of the composites were significantly enhanced by the addition of the CNTs. The highest content of CNTs in the composites was 6 wt%. The composites containing 6 wt% CNTs and 4 wt% BG exhibited the same mechanical strength as the pure PEEK. The bioactivity of the PEEK when immersed in simulated body fluid (SBF) was improved by incorporating BG into the composites. These new ternary composite materials which exhibit satisfactory mechanical properties and a high degree of bioactivity have great potential to meet the demand for bone-substitute materials.
    Journal of Polymer Research 20(8). · 2.02 Impact Factor
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    ABSTRACT: Control of dimensional stability is crucial for using electrospun membranes in biomedical and tissue engineering applications. In this study, the contraction of electrospun membranes of poly(l-lactide-co-glycolide) (PLLGA) after stretch was investigated. Then, by adding PLLGA-b-polyethylene glycol (PLLGA-PEG), the contraction of the membranes was controlled. In addition, the mechanical properties of the membranes were investigated. On the basis of the strain–stress behavior of the membranes, an elongation of 50 % was used to investigate the orientation degrees of the membrane fibers. On the basis of the morphology of the stretched membranes, the contraction was found to depend on the orientation degree of fibers after stretch. A linear relationship between the contraction and degree of orientation after stretch was confirmed. Two-dimensional fast Fourier transform (2D FFT) analysis of the scanning electron microscopy (SEM) images of the membranes was used to quantify the orientation degree. It was surmised that the different orientation degrees were responsible for the different morphologies and thermal behaviors of the membranes.
    Journal of Polymer Research 19(12). · 2.02 Impact Factor
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    ABSTRACT: Amino acid endcapped poly(p-dioxanone)s (APPDOs) were synthesized, using either glycine, alanine, leucine, or phenylalanine to initiate the ring-opening polymerization reaction of p-dioxanone (PDO). The structures of the APPDOs were characterized by 1H NMR spectroscopy. The initiation of polymerization by the amino acids was demonstrated via the relation between the average molecular weight and the molar feed ratio N(PDO):N(amino acid) using GPC and capillary viscosity measurements. The nonisothermal and isothermal crystallization properties of the APPDOs were studied by DSC. The Avrami equation was suitable for analyzing the isothermal crystallization of the APPDOs; the constant k and the exponent n in this equation were calculated by plotting lg[−ln(1 − X t )] versus lgt. The crystallization rate (as assessed by studying the parameter τ 1/2) was found to increase with average molecular weight for APPDOs with the same amino acid end-group. However, for APPDOs with different end-groups, the crystallization rate was found to decrease as the size of the end-group increases.
    Journal of Polymer Research 20(4). · 2.02 Impact Factor

Publication Stats

78 Citations
35.48 Total Impact Points

Institutions

  • 2004–2013
    • Chinese Academy of Sciences
      • Graduate School
      Peping, Beijing, China
  • 2005–2010
    • Northeast Institute of Geography and Agroecology
      • Graduate School
      Beijing, Beijing Shi, China
  • 2007–2009
    • Sichuan University
      • • State Key Laboratory of Polymer Material Engineering
      • • College of Chemistry
      Hua-yang, Sichuan, China