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One of the obstacles limiting the application of electrospun scaffolds for tissue engineering is the nanoscale pores that inhibit cell infiltration. In this article, we describe a technique that uses ice crystals as templates to fabricate cryogenic electrospun scaffolds (CES) with large three-dimensional and interconnected pores using poly(D,L-lactide) (PLA). Manipulating the humidity of the electrospinning environment the pore sizes are controlled. We are able to achieve pore sizes ranging from 900 +/- 100 microm(2) to 5000 +/- 2000 microm(2) depending on the relative humidity used. Our results show that cells infiltrated the CES up to 50 microm in thickness in vitro under static culture conditions whereas cells did not infiltrate the conventional electrospun scaffolds. In vivo studies demonstrated improved cell infiltration and vascularization in the CES compared with conventionally prepared electrospun scaffolds. In gaining control of the pore characteristics, we can then design CES that are optimized for specific tissue engineering applications.

Due to their attractive mechanical properties, bioinert zirconia bioceramics are frequently used in the high load-bearing sites such as orthopaedic and dental implants, but they are chemically inert and do not naturally form a direct bond with bone and thus do not provide osseointegration. A CO2 laser was used to modify the surface properties with the aim to achieve osseointegration between bioinert zirconia and bone. The surface characterisation revealed that the surface roughness decreased and solidified microstructure occurred after laser treatment. Higher wettability characteristics generated by the CO2 laser treatment was primarily due to the enhancement of the surface energy, particularly the polar component, determined by microstructural changes. An in vitro test using human fetal osteoblast cells (hFOB) revealed that osteoblast cells adhere better on the laser treated sample than the untreated sample. The change in the wettability characteristics could be the main mechanism governing the osteoblast cell adhesion on the YPSZ.

ABSTRACT:The reactions between polymeric diphenyl methane diisocyanate (polymeric MDI) and conventional polyols to produce foamed polyurethane products are well documented and published. Current polyurethane foams are predominantly produced from these reactions whereby the polyol components are usually obtained from petrochemical processes. This article describes a new development in polyurethane foam technology whereby a renewable source of polyol derived from refined-bleached-deodorized (RBD) palm oil is used to produce polyurethane foams. Using very basic foam formulation, rigid polyurethane foams were produced with carbon dioxide as the blowing agent generated from the reaction between excess polymeric MDI with water. The foams produced from this derivatized RBD palm oil have densities in excess of 200 kg/ m 3 and with compression strengths greater than 1 MPa.

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Electrospun scaffolds have been increasingly used in tissue engineering applications due to their size-scale similarities with native extracellular matrices. Their inherent fibrous features may be important in promoting cell attachment and proliferation on the scaffolds. In this study, we explore the technique of fabricating electrospun fibers with nano-sized porous surfaces and investigate their effects on the attachment of porcine esophageal epithelial cells (PEECs). Porosity was introduced in electrospun poly(D,L-lactide) fibers by creating vapor-induced phase separation conditions during electrospinning. The nanoporous fiber scaffolds were mechanically weaker than the conventional solid fiber scaffolds and solvent-cast films of the same polymer. However, the nanoporosity of the fibers was found to enhance the levels of adsorbed protein from a dilute solution of fetal bovine serum. The amount of protein adsorbed by nanoporous fiber scaffolds was approximately 80% higher than the solid fiber scaffolds. This corresponds to an estimated 62% increase in surface area of the porous fibers than the solid fibers. By comparison, the solvent-cast films adsorbed low levels of protein from the FBS solution. In addition, the porous fibers were found to be advantageous in enhancing initial cell attachment as compared with the solid fibers and solvent-cast films. It was observed that nanoporous fiber scaffolds seeded with PEECs had significantly greater number of viable cells attached than the solid fiber scaffolds after 10 and 24 h in culture. Hence, our results indicate that nanosized porous surfaces on electrospun fibers enhance both protein adsorption and cell attachment. These findings provide a method to improve cell-matrix interactions of electrospun scaffolds for tissue engineering applications.

The identification of a three dimensional constitutive model is useful for describing the complex mechanical behavior of a nonlinear and anisotropic biological tissue such as the esophagus. The inflation tests at the fixed axial extension of 1, 1.125, and 1.25 were conducted on the muscle and mucosa layer of a porcine esophagus separately and the pressure-radius-axial force was recorded. The experimental data were fitted with the constitutive model to obtain the structure-related parameters, including the collagen amount and fiber orientation. Results showed that a bilinear strain energy function (SEF) with four parameters could fit the inflation data at an individual extension very well while a six-parameter model had to be used to capture the inflation behaviors at all three extensions simultaneously. It was found that the collagen distribution was axial preferred in both layers and the mucosa contained more collagen, which were in agreement with the findings through a pair of uniaxial tensile test in our previous study. The model was expected to be used for the prediction of stress distribution within the esophageal wall under the physiological state and provide some useful information in the clinical studies of the esophageal diseases.

Chitosan is not only a nontoxic, biocompatible, and biodegradable polymer, but has also a chemical structure similar to glycosaminoglycans (GAGs), which promote scarless wound healing of skin. In this study, chitosan membranes were treated with argon plasma to improve their surface hydrophilicity. The results showed that the water contact angles of these surface-treated membranes were significantly reduced from 60.76 to 11.57 degrees . The total surface energy was increased from 41.06 to 67.31 mJ/m(2), with 60-86.95% improvement in the gamma-negative component and a 20% difference in the nonpolar component. Argon-plasma-treated chitosan membranes exhibited excellent attachment, migration, and proliferation of the human-skin-derived fibroblasts (hSFs) compared to the untreated ones. It was found that the duration of argon-plasma treatment influenced the cell proliferation, and the optical densities in MTT assay were enhanced. Argon-plasma treatment improved the surface hydrophilicity of chitosan membranes and promoted the attachment and proliferation of hSFs.