Biomedical subjects

Shenguo Wang

Publications and source records attributed to Shenguo Wang.

27 records · Page 2Linked to original sources

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↗

PubMed2002

Effect of a cyclosporine A delivery system in corneal transplantation.

OBJECTIVE: To test the immunosuppressive effect of cyclosporine (Cs) in a polymer placed in the anterior chamber of corneal allograft recipients. METHODS: Wistar inbred rats with vascularized corneas were recipients of corneal allografts from Sprague-Dawley donor rats. Rats underwent penetrating keratoplasty and were divided randomly into four groups: untreated control animals (UCA); Cs-polymer anterior chamber recipients (CPA); co-polymer subconjunctival recipients (CPS); and Cs-olive oil drop recipients (COO). Grafts were examined by slit lamp every 3 days and clinical conditions were scored. Cs concentration in the aqueous humor was assayed at 1, 2, and 4 weeks. At 1, 2 and 4 weeks after transplantation, the operated eyes were collected for histopathological evaluation of the grafts. RESULTS: The median survival time of the allografts was 8.2 +/- 1.48 days for the UCA group, 11.4 +/- 2.50 days for the CPS group, and 17.0 +/- 2.00 days for the CPA group. There was a statistically significant difference (P < 0.05) between survival time of the allografts in the animals of the CPA group compared to the other groups of graft recipients. Significantly higher concentrations of Cs were found in the eyes given an anterior chamber implant of Cs-polymer, compared to other treatment groups or untreated rats. A transient inflammatory response in the anterior chamber was observed in the CPA group. CONCLUSIONS: Cs-polymer placed in the anterior chamber significantly prolongs corneal allograft survival time in a high risk corneal graft rejection model. This intraocular delivery system may be a valuable adjunct for the suppression of immune graft rejection.

Animals↗

PubMed2002

[Prolongation of corneal allograft survival in mice with a cyclosporine drug delivery system implant].

OBJECTIVE: To study the immunosuppressive effect and mechanism of cyclospoirne A (CsA) in a drug delivery system (DDS) implanted in the anterior chamber of corneal allograft in a mouse model. METHODS: Female BALB-c mice were the recipients of corneal allografts from C57BL-6 donor mice. A total of 90 allografts were implanted in penetrating keratoplasty. Cyclosporine A was incorporated into a polyactide-coglycolide-co-caprolactone (PGLC) polymer and small pellets of CsA PGLC were placed into the anterior chamber of recipient mouse eyes at the time of transplantation. Control recipients did not receive any implants or received implants containing no drug. The clinical condition of the grafts was observed by slit-lamp microscope every three days and the tempo and the time of rejection of the grafts were recorded. Some grafts were removed at weekly intervals for histopathological and immunohistopathological analysis. RESULTS: The corneal allografts of the mice with CsA PGLC implanted (group A) prolonged their survival time significantly with a median of 35 +/- 3 days. In contrast, the median survival time of corneal allografts in eyes of recipients receiving implants containing no drug (group B) and eyes receiving allografts but no implant (group C) was 14 +/- 3 days. The differences between A and B and between A and C group were statistically very significant (P < 0.001). The corneal donor of the eyes treated with the CsA PGLC implant remained clear until the implant pallet began to shrink in size and graft rejection began. The grafts which came under an immune attack progressively were vascularized and thickened, and became opaque. In the control animals, the development of the immune response overlapped with the acute inflammatory reaction, which occurred in the mouse eye following corneal transplantation. Histopathologically and immunohistopathologically, the grafts, ciliary body and iris which were subjected to an immune response contained a dense infiltrate of neutrophils, CD(4)(+) and CD(8)(+) T lymphocytes, and many CD(11B)(+) inflammatory cells including macrophages and Langerhans cells in the control rejection mice. This cellular infiltrate was decreased in the recipients, and delayed in ciliary body and iris whose corneas were transplanted with the CsA PGLC implant in the anterior chamber. CONCLUSION: Intraocular CsA in a sustained release system as a means significantly prolongs corneal allograft survival in mouse model and protests corneal allografts from acute, immune-mediated rejection.

Animals↗

PubMedDate not supplied

Synthesis and properties of star-shaped polylactide attached to poly(amidoamine) dendrimer.

Star-shaped polylactide was synthesized by bulk polymerization of lactide with poly(amidoamine) (PAMAM) dendrimer as initiator, which was marked as PAMAM-g-PLA for simplicity. The nonlinear architecture of PAMAM-g-PLA was confirmed by gel permeation chromatograph, nuclear magnetic resonance, and differential scanning calorimetry analysis. Unlike the linear polylactide (PLA) with similar molecular weight, PAMAM-g-PLA had a higher hydrophilicity and a faster degradation rate because of shortened polymer chains and increased polar terminal endgroups due to its branch structure. The highly branched structure significantly accelerated the release of water-soluble bovine serum albumin from PAMAM-g-PLA microspheres, whereas the linear PLA with similar molecular weight exhibited an initial time lag release. This star polymer may have potential applications for hydrophilic drug delivery in tissue engineering, including growth factor and antibodies to induce tissue regeneration, by adjusting the chain lengths of PLA branches.

Animals↗