D P Quan | PubMed Health

PubMed2001

A conductive polypyrrole based ammonium ion selective electrode.

In view of the development of miniaturized sensor arrays, a solid-contact ammonium ion selective electrode has been investigated. A conductive polypyrrole film was electrochemically deposited on a glassy carbon surface and used as an internal solid contact layer between the sensing membrane and solid electrode surface. A systematic evaluation of the important parameters affecting the electromotive force (emf) response is presented. The performances of this solid-contact sensor were verified using a batch-mode measurement setup and a wall-jet flow cell system. The designed sensor exhibited excellent selectivity for the primary ion and a linear response over the pNH4+ range 1-5 with a slope of 56.3 mV decade(-1) . The sensor has a fast response and is relatively robustness, and was also used to determine ammonium concentrations in natural waters, with promising results.

Electrochemistry↗

PubMed2001

[Neocartilage formation in vitro using transduced mesenchymal stem cells cultured on biomimetic biodegradable polymer scaffolds].

OBJECTIVE: To investigate the effect of transforming growth factor (TGF) beta 1 gene transfection on the growth of mesenchymal stem cells(MSCs) and to evaluate a new biomimetic biodegradable polymer as scaffolds for applications in articular cartilage tissue engineering. METHODS: Principles of tissue engineering were combined organically with principles of gene therapy to produce cultured periosteum-derived MSCs transduced with the full-length rat TGF-beta 1 cDNA in vitro. These cells were then seeded onto three-dimensional porous poly-DL-lactide scaffolds modified with poly-L-lysine that mimicked cell-binding domains found on natural extracellular matrix to promote specific cell adhesion. The adhesion, proliferation, and differentiation of the transfected MSCs were examined with scanning electron microscope within 2 weeks. RESULTS: All cells adhered to the biomimetic matrices well, but more cartilage-like tissue was formed for TGF-beta 1 gene modified MSCs/scaffolds composites than for the control groups. Transfer of gene encoding TGF-beta 1 to MSCs promoted its proliferation and differentiation significantly. CONCLUSIONS: The TGF-beta 1 gene transduced MSCs/biomimetic matrix composites used in this study was the first attempt to apply the principles of molecular tissue engineering for articular cartilage repair. This new molecular tissue engineering approach could be of potential benefit to repair damaged articular cartilage, especially in osteoarthritis. The new biomimetic biodegradable polymer matrices modified with biomolecules not only have good structural compatibility, but also have better interfacial compatibility and bioactivity, and can be used as scaffolds for articular cartilage tissue engineering.

Animals↗