David Vu

Preparation and evaluation of the electrospun chitosan/PEO fibers for potential applications in cartilage tissue engineering

Fibrous materials have morphological similarities to natural cartilage extracellular matrix and have been considered as candidate for bone tissue engineering scaffolds. In this study, we have evaluated a novel electrospun chitosan mat composed of oriented sub-micron fibers for its tensile property and biocompatibility with chondrocytes (cell attachment, proliferation and viability). Scanning electronic microscope images showed the fibers in the electrospun chitosan mats were indeed aligned and there was a slight cross-linking between the parent fibers. The electrospun mats have significantly higher elastic modulus (2.25 MPa) than the cast films (1.19 MPa). Viability of cells on the electrospun mat was 69% of the cells on tissue-culture polystyrene (TCP control) after three days in culture, which was slightly higher than that on the cast films (63% of the TCP control). Cells on the electrospun mat grew slowly the first week but the growth rate increased after that. By day 10, cell number on the electrospun mat was almost 82% that of TCP control, which was higher than that of cast films (56% of TCP). The electrospun chitosan mats have a higher Youngs modulus (P <0.01) than cast films and provide good chondrocyte biocompatibility. The electrospun chitosan mats, thus, have the potential to be further processed into three-dimensional scaffolds for cartilage tissue repair.

A facile method to deposit zeolites Y and L onto cellulose fibers

Abstract Zeolite (Y and L)/cellulose composites are synthesized from natural cellulose fibers pre-treated with NaOH, KOH or Na2SiO3, and preformed zeolite powders. Several techniques such as diffuse reflectance infrared spectroscopy, X-ray diffraction, scanning electron microscopy and BET specific surface area measurements were used to characterize these materials. Successful synthesis depends on extent of water removal from open reactors, fiber pre-treatment and reaction temperature, reaction time, and initial water:zeolite:fiber ratio. One important trait of the materials reported in this study is that their zeolite content becomes stable on washing with water at 373 K for several hours.

Hybrid TiO2-SiO2 organic/inorganic gels as catalysts for olefin epoxidation

Abstract Hybrid TiO2–SiO2 xerogels were treated at different temperatures, and used as olefin epoxidation catalysts. All samples displayed a very high selectivity toward formation of cyclooctene oxide from cis-cyclooctene, in the presence of hydrogen peroxide and methanol. ‘All-inorganic’ (entirely TEOS-based) preparations are more subject to Ti leaching during reaction than the hybrid materials and as a consequence, they display much poorer activity recovery after recovery and re-use. The higher hydrophobicity of the hybrid samples relative to that of the conventional TiO2–SiO2 alcogel is demonstrated by dynamic adsorption experiments using an oscillating balance reactor.