Improving pore interconnectivity in polymeric scaffolds for tissue engineering.
ABSTRACT A new scaffold fabrication technique aiming to enhance pore interconnectivity for tissue engineering has been developed. Medical grade poly(lactic acid) was utilized to generate scaffolds by a solvent-evaporating/particulate-leaching technique, using a new dual-porogen system. Water-soluble sodium chloride particles were used to control macro-pore size in the range 106-255 microm, while organic naphthalene was utilized as a porogen to increase pore interconnections. The three-dimensional (3D) morphology of the scaffolds manufactured with and without naphthalene was examined by optical coherence tomography and scanning electron microscopy. The mechanical properties of the scaffolds were characterized by compression tests. MG63 osteoblast cells were seeded in the scaffolds to study the cell attachment and viability evaluated by confocal microscopy. It was revealed that introducing naphthalene as the second porogen in the solvent-evaporating/particulate-leaching process resulted in improvement of the pore interconnectivity. Cells grew in both scaffolds fabricated with and without naphthalene. They exhibited strong green fluorescence when using a live/dead fluorescent dye kit, indicating that the naphthalene in the scaffold process did not affect cell viability.
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ABSTRACT: In this study, the use of triblock (A–B–A) oligomers of ɛ-caprolactone (ɛ-CL) (A) and PEG400 (B) as stabilizers (SB) for the copolymerization of L-lactide (LLA) and ɛ-CL in supercritical carbon dioxide (scCO2) was investigated. To determine the effect of CO2-philic and polymer-philic segments on copolymerization, oligomers with three different average molecular weights (Mw=2000–6000 Da) were synthesized by changing the PEG400/ɛ-CL ratio. Copolymerizations were confirmed by 1H-nuclear magnetic resonance (NMR), 13C-NMR and differential scanning calorimeter data. It was possible to copolymerize LLA and ɛ-CL in scCO2 without any SB; however, the polymerization yields and average molecular weights were low, and significant aggregate formations were detected. Recipes featuring only 5% SB were successfully applied to reach high polymerization yields of ∼85% and polymers with average molecular weights greater than 20 kDa. When the polymer-philic segment of the SB increased, both the yield and molecular weight of the copolymer also increased significantly, resulting in white powdery products.Polymer Journal 07/2011; 43(9):785-791. · 1.55 Impact Factor
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ABSTRACT: Miscibility and foaming of poly(l-lactic acid) (PLLA) in carbon dioxide+acetone mixtures have been explored over the temperature and pressure ranges from 60 to 180°C and 14 to 61MPa. Liquid–liquid phase boundaries were determined in a variable-volume view-cell for polymer concentrations up to 25wt% PLLA and fluid mixtures containing 67–93wt% CO2 over a temperature range from 60 to 180°C. Even though not soluble in carbon dioxide at pressures tested, the polymer could be completely solubilized in mixtures of carbon dioxide and acetone at modest pressures.Foaming experiments were carried out in different modes. Free-expansions were carried out by exposure and swelling in pure carbon dioxide in a view-cell followed by depressurization. Foaming experiments were also carried out within the confinement of specially designed molds with porous metal surfaces as boundaries to direct the fluid escape path and to generate foams with controlled overall shape and dimensions. These experiments were conducted in pure carbon dioxide and also in carbon dioxide+acetone fluid mixtures over a wide range of temperatures and pressures. Foaming in carbon dioxide+acetone mixtures was limited to 1 and 4wt% acetone cases. Microstructures were examined using an environmental scanning electron microscope (ESEM). Depending upon the conditions employed, pore diameters ranging from 5 to 400μm were generated. At a given temperature, smaller pores were promoted when foaming was carried out by depressurization from higher pressures. At a given pressure, smaller pores were generated from expansions at lower temperatures. Foams with larger pores were produced in mixtures of carbon dioxide with acetone.Journal of Supercritical Fluids - J SUPERCRIT FLUID. 01/2010; 54(3):296-307.
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ABSTRACT: In this study, poly(glycerol-co-sebacate-co-ε-caprolactone) (PGSCL) elastomers were synthesized for the first time from the respective monomers. The structural analysis of PGSCL elastomers by nuclear magnetic resonance ((1) H-NMR) and Fourier transform infrared spectroscopy (FTIR) revealed that the elastomers have a high number of hydrogen bonds and crosslinks. X-ray diffraction (XRD) and thermal analysis indicated an amorphous state. Differential scanning calorimetry (DSC) analysis showed that the elastomers has a glass transition temperature (Tg ) of -36.96°C. The Young's modulus and compression strength values were calculated as 46.08 MPa and 3.192 MPa, respectively. Calculations based on acid number and end groups analysis revealed a number average molecular weight of 148.15 kDa. Even though the foaming studies conducted by using supercritical CO2 resulted in a porous structure; the obtained morphology tended to disappear after 48 h, leaving small cracks on the surface. This phenomenon was interpreted as an indication of self-healing due to the high number of hydrogen bonds. The PGSCL elastomers synthesized in this study are flexible, robust to compression forces and have self-healing capacity. Thanks to good biocompatibility and poor cell-adhesion properties, the elastomers may find diverse applications where a postoperative adhesion barrier is required. Copyright © 2013 John Wiley & Sons, Ltd.Journal of Tissue Engineering and Regenerative Medicine 05/2013; · 4.43 Impact Factor