Biomedical subjects

Jianzhong Bei

Publications and source records attributed to Jianzhong Bei.

At least 19 recordsLinked to original sources

PubMed2006

The effect of oxygen plasma pretreatment and incubation in modified simulated body fluids on the formation of bone-like apatite on poly(lactide-co-glycolide) (70/30).

In this study, biodegradable poly(lactide-co-glycolide) (PLGA) (70/30) films and scaffolds were first treated with oxygen plasma and then incubated in a modified simulated body fluid 1.5SBF0 to prepare a bone-like apatite layer. The formation of the apatite and its influence on osteoblast-like cells growth were investigated. It was found that the bone-like apatite formability of PLGA(70/30) was enhanced by plasma pretreatment. The changes of surface chemistry and surface topography induced by oxygen plasma treatment were both effective for apatite formation. The apatite formability increased with increasing plasma-treating time. Under a treating condition of 20 W for 30 min, oxygen plasma treatment could penetrate into the inner scaffold. After 6 days incubation, the apatite formed in plasma-treated scaffold was better distributed than in untreated scaffold, and the weight and mechanical strength of the plasma-treated scaffold were both enhanced. Compared with PLGA(70/30), the apatite layer formed on oxygen plasma-treated PLGA(70/30) surface enhanced adhesion and proliferation of OCT-1 osteoblast-like cell, but had no significant effect on cell's ALP activity at day 7. A prolonged investigation is being in process to further verify the bone-like apatite effects on osteogenic differentiation.

Apatites↗

PubMed2006

Manufacturing and morphology structure of polylactide-type microtubules orientation-structured scaffolds.

Tissue engineering using scaffold not only should have biodegradability and a certain 3D structure, but also its morphology structure should be mimetic to that of the repaired natural tissue. So to manufacture the scaffold with a biomimetic structure as the natural tissues is important. In this research, highly porous poly(L-lactic acid) (PLLA) and poly(L-lactic-co-glycolic acid) (PLGA) scaffolds with microtubules orientation structure were designed and fabricated by using dioxane as solvent and an improved thermal-induced phase separation (TIPS) technique. All the factors which will affect solvent crystallization and microtubules orientation structure of the scaffold, such as the type of the solvent and polymer, concentration of the polymer solution, and temperature-gradient of the system have been studied carefully. So the porosity, diameter, tubular morphology and orientation of the microtubules could be controlled by adjusting the concentration of the polymer solution and temperature-gradient of the system. The scaffold with diameter of microtubules from 40 to 240microm and high porosity up to 96% could be obtained by adjusting temperature-gradient during the TIPS process. By increasing concentration of the polymer solution the regularity of the microtubular scaffold has been improved and the thickness of wall of the microtubules has been increased as well. In vitro cell culture results show that after the scaffolds have been improved by the ammonia plasma treatment and then collagen anchorage method, the human transparent cartilage cells H144, could be seeded deeply into the microtubules orientation-structured scaffolds and grew well there.

Biocompatible Materials↗

PubMed2006

Influences of ammonia plasma treatment on modifying depth and degradation of poly(L-lactide) scaffolds.

Hydrophobicity of poly(L-lactide) scaffolds is a main drawback in obtaining a sufficient mass of seeded cells for satisfying the requirements of tissue engineering. Plasma treatment is a useful technique to enhance the hydrophilicity of the scaffolds. However, the effect of this technique on the modifying depth and degradation of the scaffolds should be considered. In this paper, the influence of NH3 plasma treatment on the modifying depth and degradation of scaffolds were investigated. The results showed that the modifying depth of the scaffolds increased with treating time and the plasma power ranging from 20 to 80 W influenced the depth slightly. However, the degradation of the scaffolds increased with increasing treatment time and plasma power. The results also showed that the plasma intruded the scaffolds gradually from top to bottom. For a 4 mm thick scaffold, the optimized treatment condition was 20 W of power in a 30 Pa ammonia atmosphere for 30 min of treating time. Under this condition, the integrity of scaffold could be relatively well kept. NH3 plasma treatment enabled the penetration of cells into scaffolds and facilitated the proliferation of cells in them.

3T3 Cells↗

PubMed2006

Porcine-derived xenogeneic bone/poly(glycolide-co-lactide-co-caprolactone) composite and its affinity with rat OCT-1 osteoblast-like cells.

Porcine-derived xenogeneic bone (PDXB) was derived from cancellous bone of adult porcine. Its morphology and structure were characterized by SEM, FTIR and XRD. A series of composite films consisting of PDXB and poly(glycolide-co-lactide-co-caprolactone) (PGLC) polymer were prepared. Because of the introduction of PGLC polymer, the PDXB/PGLC composites especially PDXB/PGLC(30/70) and PDXB/PGLC(50/50) showed good processability and mechanical properties. In addition, the hydrophilicity of the composites was enhanced as well since the PDXB component was hydrophilic. Osteoblast-like cells (OCT-1) were used as an in-vitro model to assess the affinity of the PDXB/PGLC composites. It was found that compared with the pure PGLC film, PDXB/PGLC(30/70) and PDXB/PGLC(50/50) composite films promoted cell attachment, proliferation and ALP (alkaline phosphatase) activity obviously. In addition, the cells preferred growing on the areas of exposed PDXB. It was considered that the hydrophilicity, osteoconductivity and appropriate surface roughness (Sa=3.30, 4.00 microm) induced by PDXB facilitate cell growth. However, the introduction of too much PDXB, such as PDXB/PGLC(70/30) film, would obtain an adverse effect on the cell growth since the value of Sa was up to 7.33 microm. It indicated that only the composites with appropriate surface topography could favor cell growth. Surface topography probably has a more important effect on cell growth process than surface chemistry.

Animals↗

PubMed2005

Bulk and surface modifications of polylactide.

This article reviews various methods of modifying the bulk and surface properties of poly(lactic acid) (PLA) so that the polymer may be used as a drug carrier in a drug delivery system (DDS) and as a cell scaffold in tissue engineering. Copolymerization of lactide with other lactone-type monomers or monomers with functional groups such as malic acid, copolymerization of lactide with macromolecular monomer such as poly(ethylene glycol) (PEG) or dextran, as well as blending polylactide and natural derivatives and other methods of bulk modification are discussed. Surface modifications of PLA-type copolymers, such as surface coating, chemical modification, and plasma treatment are described. Cell culture technology proves the efficiency of bulk and surface modification and the potential application of PLA in tissue engineering.

Absorbable Implants↗

PubMed2005

Preparation and evaluation of poly(L-lactide-co-glycolide) (PLGA) microbubbles as a contrast agent for myocardial contrast echocardiography.

A kind of absorbable PLGA microbubble-based contrast agent (PLGA microspheres with porous or hollow inner structure) was fabricated by an improved double emulsion-solvent evaporation method. The contrast efficiency was evaluated and proved both in vitro and in vivo. By adjusting the polymer concentration and volume of the inner aqueous phase during the fabrication of microbubbles, the inner structure of the microbubbles could be controlled. Both air-filled and perfluoropropane-filled microbubbles can opacify the left ventricle. However, when compared with air-filled microbubbles, perfluoropropane-filled microbubbles can produce significantly longer enhancement in left ventricle in the dog model due to the lower diffusivity and lower solubility of perfluoropropane in blood. A suspension of perfluoropropane-filled PLGA microbubbles (1.8 microm average microbubbles size, 2 x 10(8) microbubbles/mL concentration) has successfully and safely achieved myocardial opacification in closed-chest dogs. A perfusion defect was observed in both of the two dogs with acute myocardial infarction with Power Contrast Imaging (PCI) triggered technology. In the examination of contrast in both ventricular and myocardial opacification, the high mechanical index (MI) was found to have superior contrast sensitivity over the low MI for PLGA-based contrast agents.

Acoustics↗

PubMed2005

Adhesion and proliferation of OCT-1 osteoblast-like cells on micro- and nano-scale topography structured poly(L-lactide).

The impact of the surface topography of polylactone-type polymer on cell adhesion was to be concerned because the micro-scale texture of a surface can provide a significant effect on the adhesion behavior of cells on the surface. Especially for the application of tissue engineering scaffold, the pore size could have an influence on cell in-growth and subsequent proliferation. Micro-fabrication technology was used to generate specific topography to investigate the relationship between the cells and surface. In this study the pits-patterned surfaces of polystyrene (PS) film with diameters 2.2 and 0.45 microm were prepared by phase-separation, and the corresponding scale islands-patterned PLLA surface was prepared by a molding technique using the pits-patterned PS as a template. The adhesion and proliferation behavior of OCT-1 osteoblast-like cells morphology on the pits- and islands-patterned surface were characterized by SEM observation, cell attachment efficiency measurement and MTT assay. The results showed that the cell adhesion could be enhanced on PLLA and PS surface with nano-scale and micro-scale roughness compared to the smooth surfaces of the PLLA and PS. The OCT-1 osteoblast-like cells could grow along the surface with two different size islands of PLLA and grow inside the micro-scale pits of the PS. However, the proliferation of cells on the micro- and nano-scale patterned surface has not been enhanced compared with the controlled smooth surface.

Animals↗

PubMed2004

Characterization of surface property of poly(lactide-co-glycolide) after oxygen plasma treatment.

In this study, poly (lactide-co-glycolide) (PLGA) films were treated by oxygen plasma. The surface structure, topography and surface chemistry of treated PLGA films were characterized by contact angle measurement, scanning electron microscope observation, atomic force microscopy, and X-ray photoelectron spectrum analysis. The cell affinity of the oxygen plasma treated films was evaluated under dynamic conditions by Parallel Plate Flow Chamber (PPFC). The results showed that the hydrophilicity increased greatly after oxygen plasma treatment. High quantities of -C-O groups, such as hydroxyl and peroxyl groups could be incorporated into the surface of PLGA (70/30) by controlling appropriate plasma treatment conditions. Moreover, the oxygen plasma treatment resulted in formation of peaks and valleys on the sample surfaces, and the roughness increased with treatment time. Cells stretched very well and the ability to endure the shear stress was improved greatly after the PLGA (70/30) was modified by appropriate plasma treatment, i.e. under 50W for 2 or 10 min. However, when the treatment time was increased to 20 min, the percentage of adherent cells on the roughest surface decreased because the content of polar groups incorporated onto the surface decreased. The results showed that improved cell adhesion was attributed to the combination of surface chemistry and surface morphology of PLGA during plasma etching.

Animals↗

PubMed2004

Synthesis and cell affinity of functionalized poly(L-lactide-co-beta-malic acid) with high molecular weight.

A novel functionalized biodegradable poly(L-lactide-co-beta-benzyl malolactonate) (p-PLMA) with high molecular weight was synthesized through ring-opening copolymerization. Three p-PLMA copolymers with different beta-benzyl malolactonate content were synthesized. The molecular weight (M(w)) and tensile strength of the copolymer with 4 mol% beta-benzyl malolactonate content were 179,800 and 19.0MPa respectively, the molecular weight (M(w)) and tensile strength of p-PLMA decreased with beta-benzyl malolactonate content increasing. The hydrophilicity of the de-protected product: poly(L-lactide-co-beta-malic acid) (d-PLMA) increased with malic acid content increasing. The results of 3T3 mice fibroblasts cultivated on d-PLMA films showed that the cell adhesion on d-PLMA was better than that of PLLA and the cell attached efficiency of d-PLMA with 8 mol% malic acid content was the highest. The cells grew well both on the surface and inside of d-PLMA scaffolds. The cell affinity of d-PLMA was better than that of PLLA.

3T3 Cells↗

PubMed2003

Plasma-treated, collagen-anchored polylactone: Its cell affinity evaluation under shear or shear-free conditions.

Poly(L-lactic acid)(PLLA) and poly(L-lactic-co-glycolic acid) (PLGA) (85/15) were modified by plasma treatment. Then they were collagen anchored (PT/CA), and the cell affinity was evaluated by cell culture under shear or shear-free conditions. A convenient and "intuitionistic" dyeing method has been proposed for measuring the modified depth when plasma treatment is applied for the treatment of porous scaffolds. A parallel plate flow chamber was developed in order to study the cell affinity of a material under shear stress. Our results show that a porous scaffold can be modified by plasma treatment and that a depth of about 4.0 mm for this modification can be reached with NH(3) plasma treatment (50 w, 20 Pa, 5 min). PT/CA modification is an effective surface modification method for facilitating cell transplantation and improving the cell affinity of three-dimensional porous cell scaffolds in tissue engineering. It can solve the problem of non-uniform cell distribution in most synthetic porous cell scaffolds. Using the flow chamber system, a series of quantitative data, including cell adherent fraction, cell area, and mean shape, were compared to evaluate the cell affinity of PLLA before and after PT/CA modification. The results indicate that the quality of cell attachment on PT/CA-modified PLLA apparently is better than that on unmodified PLLA. The flow chamber system potentially may be a tool for evaluating surface modification methods.

3T3 Cells↗

PubMed2003

Acceleration effect of basic fibroblast growth factor on the regeneration of peripheral nerve through a 15-mm gap.

In this study, nerve guides composed of poly(D,L-lactide) (PDLLA) were fabricated and used in the repair of transected sciatic nerves (15-mm gaps) of rats. Nerve guides with a two-ply structure (inner layer dense, outer layer microporous) were prepared by controlling the solvent evaporation rate. Then basic fibroblast growth factor (bFGF) was embedded in the inner layer of the nerve guides. Thus the inner dense layer not only could prevent the ingrowth of fibroblast and avoid the outgrowing nerve cable, but it also could retain the released bFGF in the guide lumen. The outer porous layer allowed vascular ingrowth and the diffusion of essential nutrients into the guide lumen. The data show that by using this nerve guide, the transected 15-mm sciatic nerve was regenerated successfully within 4 months. The recovery of function of the regenerated nerves was significantly accelerated by bFGF, as indicated by an electrostimulation test and histologic assays. In addition, the bFGF retained its bioactivity during embedding and continuously was released from the matrix, as confirmed by the results of both the dorsal root ganglia (DRG) and the Schwann cell culture in the presence of PDLLA matrix containing bFGF. The released bFGF enhanced the ability of the nerve fibers to sprout from dorsal root ganglia, and it accelerated the proliferation of Schwann cells.

Animals↗

PubMed2003

Enzymatic degradation behavior and mechanism of poly(lactide-co-glycolide) foams by trypsin.

The purpose of this study is to investigate the enzymatic degradation behaviors of porous poly(lactide-co-glycolide) (PLGA) foams in the presence of trypsin, in comparison with their hydrolytic degradation. To inspect the effect of trypsin on the degradation of PLGA, both the hydrolytic and enzymatic degradation of non-porous PLGA samples were also performed. The changes of molecular weight and molecular weight distribution (polydispersity) during the degradation were determined by gel permeation chromatograph. And the changes of weight, thickness and morphology with the degradation were also measured. The degradation of PLGA displayed as two stages. In the first stage, the molecular weight of PLGA decreased continuously with degradation time, whereas little weight loss occurred. But in the second stage, the molecular weight of PLGA had decreased to a low value and was almost unchanged with time, while the sample experienced significant weight loss. And it was found that the presence of trypsin could significantly accelerate the weight loss rates of all the PLGA samples, but it caused little difference in the decrease of molecular weight and the change of PLGA composition between the enzymatic and hydrolytic degradation. Therefore, the enzymatic degradation of PLGA was still primarily a hydrolysis process. A mechanism of enzymatic degradation was proposed that the trypsin could enhance the weight loss of PLGA by acting as surfactant to push the dispersion of degradation products into water even though they could not dissolve in water.

Biocompatible Materials↗

PubMed2003

Biodegradable poly(L-lactide)-poly(ethylene glycol) multiblock copolymer: synthesis and evaluation of cell affinity.

A series of poly(L-lactide)-poly(ethylene glycol) multiblock copolymers (Multi-PLE) with high molecular weight were synthesized and successfully used to fabricate three-dimensional scaffolds. Using mouse NIH 3T3 fibroblasts as model cells, the cell affinity of various Multi-PLE copolymers was evaluated and compared with that of poly(L-lactide) (PLLA) by means of cell attachment efficiency measurement, scanning electron microscopy observation and MTT assay. On one hand, the results showed that the cell attachment efficiency on Multi-PLE 4/1(4/1 refers to the molar ratio of lactidyl units to ethylene oxide units) films was close to that on PLLA film, however, the other Multi-PLE films exhibited much lower cell attachment efficiency than PLLA film, such as Multi-PLE 2/1 and Multi-PLE 1/1, which had higher PEG content. On the other hand, it was interesting to find that cell proliferation on Multi-PLE4/1 and Multi-PLE2/1 scaffolds was better than that on PLLA scaffold, which was closely related to the improved hydrophilicity of Multi-PLE copolymers due to the incorporation of PEG in comparison with pure PLLA. The Multi-PLE copolymer scaffolds with appropriate hydrophilicity were in favor of mass transportation, and then of cell proliferation and cell affinity. It meant that the cell proliferation would be much improved by increasing the hydrophilicity of the three-dimensional scaffolds, which even outweighed the disadvantages of the cell attachment efficiency reduction with the incorporation of PEG.

3T3 Cells↗

PubMed2003

Synthesis and characterization of biodegradable polylactide-grafted dextran and its application as compatilizer.

Brush-like biodegradable polylactide-grafted dextran copolymer (PLA-g-dextran) was by a bulk polymerization reaction using a trimethylsilyl-protected (TMS) dextran as macroinitiator and stannous octoate as catalyst. After the polymerization, the TMS groups could be easily removed by immersing the copolymer in methanol for 48 h. The PLA-g-dextran copolymers were characterized by (1)H NMR, GPC and intrinsic viscosity measurements. Besides, mouse 3T3 fibroblasts were cultured on these copolymeric substrates together with pure polylactide (PLA). Although the copolymers exhibited better hydrophilicity and cell affinity compared to pure PLA because of the incorporation of glucose units and the brush-like architecture, it was found that the cells still could not migrate into the center part of scaffold made of PLA-g-dextran copolymer. In result, PLA-g-dextran copolymers themselves were not an appropriate choice for the cell scaffold material, however, it could be used as compatilizer to ameliorate the compatibility between hydrophilic dextran and hydrophobic PLA due to its amphiphilic structure, which could improve the mechanical properties of PLA/dextran blends by reducing the phase separation between PLA and dextran. Therefore, the PLA/dextran blends, which had good cell affinity and moderate mechanical strength, might be prospect cell scaffold materials.

Animals↗

PubMed2003

Cell adhesion on gaseous plasma modified poly-(L-lactide) surface under shear stress field.

A series of gases were used for plasma treatment of poly-(L-lactide) (PLLA) under various conditions such as atmosphere, electric power, pressure and time. The NH(3) was preferably selected for modifying the surface of PLLA because it can obtain appropriate hydrophilicity and surface energy with high polar component compared to other gases. Subsequently, cells were seeded onto NH(3) modified surface and exposed to 29.5N/m(2) of shear stress field by means of a parallel plate flow chamber in order to get good insight into the influence of N-containing incorporation on cell retention, cell morphology, and cell shape factor. The results showed that cell retention on the modified PLLA was much higher than that on the unmodified one. The NH(3) plasma modified PLLA with high cell affinity and resistance to shear stress was gained. Surface hydrophilicity, surface energy with high polar component and N-containing groups may play an important role in enhancing cell resistance to shear stress. It revealed that the parallel plate flow chamber is an effective device for evaluating the effects of surface modification on the cell affinity of a material.

3T3 Cells↗

PubMed2002

Fabrication and surface modification of macroporous poly(L-lactic acid) and poly(L-lactic-co-glycolic acid) (70/30) cell scaffolds for human skin fibroblast cell culture.

The fabrication and surface modification of a porous cell scaffold are very important in tissue engineering. Of most concern are high-density cell seeding, nutrient and oxygen supply, and cell affinity. In the present study, poly(L-lactic acid) and poly(L-lactic-co-glycolic acid) (70/30) cell scaffolds with different pore structures were fabricated. An improved method based on Archimedes' Principle for measuring the porosity of scaffolds, using a density bottle, was developed. Anhydrous ammonia plasma treatment was used to modify surface properties to improve the cell affinity of the scaffolds. The results show that hydrophilicity and surface energy were improved. The polar N-containing groups and positive charged groups also were incorporated into the sample surface. A low-temperature treatment was used to maintain the plasma-modified surface properties effectively. It would do help to the further application of plasma treatment technique. Cell culture results showed that pores smaller than 160 microm are suitable for human skin fibroblast cell growth. Cell seeding efficiency was maintained at above 99%, which is better than the efficiency achieved with the common method of prewetting by ethanol. The plasma-treatment method also helped to resolve the problem of cell loss during cell seeding, and the negative effects of the ethanol trace on cell culture were avoided. The results suggest that anhydrous ammonia plasma treatment enhances the cell affinity of porous scaffolds. Mass transport issues also have been considered.

Cells, Cultured↗

PubMed2002

Enhanced cell affinity of poly (D,L-lactide) by combining plasma treatment with collagen anchorage.

Surface properties of poly (D,L-lactide) (PDLLA) were modified by combining plasma treatment and collagen modification. The changes of surface properties were characterized by contact angles, surface energy, X-ray photoelectron spectra and scanning electron microscopy. The mouse 3T3 fibroblasts were used as model cells to evaluate the cell affinity of PDLLA before and after modification. Effects of different modification methods including plasma treatment, collagen coating and combining plasma treatment with collagen anchorage were investigated and compared. The results showed that the hydrophilicity and surface-free energy were improved and reduced, respectively, after each modification. Plasma pre-treatment could improve the roughness as it incorporated the polar groups and positively charged groups onto the sample surface; so the plasma pre-treated surface would benefit in anchoring more collagen tightly. As a result, cell affinity of PDLLA modified by combining plasma treatment with collagen anchorage was greatly improved. The modified materials could endure rinsing by PBS, which would facilitate further application when the modified materials were used as cells scaffold in tissue engineering.

3T3 Cells↗

PubMed2002

A novel porous cells scaffold made of polylactide-dextran blend by combining phase-separation and particle-leaching techniques.

In this study, a kind of biodegradable material was developed by blending polylactide (PLA) with natural biodegradable dextran, and a novel sponge-like scaffold made of it was fabricated thereof using solvent-casting and particle-leaching technique. To obtain a uniform blend of PLA and dextran by simple solvent-casting method, hydroxyls of dextran should be protected via trimethylsilyl (TMS) groups to make dextran soluble in organic solvents. Benzene was found among the few solvents that could dissolve this TMS-protected dextran (TMSD) well, however, it was not a good solvent for PLA. Therefore, a homogeneous mixed solution of PLA and TMSD could be obtained when a mixture of dichloroform (DCM) and benzene (v/v = 6/4) was used. By this technique, PLA-dextran blend films and even PLA films were observed a microporous structure (pore size around 5-10 microm) formation throughout the films under scanning electron microscope (SEM). Scaffolds that were prepared by dissolving PLA and TMSD in mixed solvent of DCM and benzene and using salt as porogen, were observed the formation of micropores (pore size around 5-10 microm) in the cellular walls of macropores (pore size around 100-200 microm). This microporous structure was closely related to the phase separation occurring during films or foams formation, which was mainly due to the different solubility of PLA and TMSD in benzene, as well as the different evaporation rates of DCM and benzene. In comparison with PLA, the surface and bulk hydrophilicity of PLA-dextran blend films or foams were significantly improved after the TMS groups were removed in methanol, and the results of cell culture on these polymeric substrates exhibited an enhancement on cell attachment and proliferation.

3T3 Cells↗