This paper describes the fabrication and characterization of the analytical properties of fluorescence-based zinc ion sensing glass slides and antibody based zinc sensors and their application in monitoring zinc release from beta pancreatic cells. The zinc ion indicator ZnAF-2 {6-[N- [N', N'-bis (2-pyridinylmethyl)-2-aminoethyl] amino-3',6'-dihydroxy-spiro[isobenzofuran-1(3H),9'-[9H] xanthene]-3-one} was modified to include a sufficiently long linking aliphatic chain, with a terminal carboxyl functional group. The activated carboxyl-modified ZnAF-2 was conjugated to the amino silanized surface of glass slides and to free amino groups of the A2B5 antibody molecules. The sensors were used to monitor zinc ion release events from glucose-stimulated pancreatic cells.
The paper describes the fabrication, characterization and applications of novel luminescent quantum dots
fluorescence resonance energy transfer (FRET) based enzymatic activity probes. The luminescent probes are
based on FRET between luminescent quantum dots that serve as donors and rhodamine acceptors that are
immobilized to the surface of the quantum dots through peptide linkers that contain selective enzymatic cleavage
sites. Upon enzymatic cleavage of the peptide linkers the rhodamine molecules no longer provide an efficient
energy transfer channel to the quantum dots, which lightes up the initially quenched the quantum dots. The
quantum dots based probes were applied for detecting enzyme activity and screening enzyme inhibitors. They
were also used for the measurement of extracellular matrix metallproteinases (MMPs) activity in normal and
cancerous breast cells tissues.
In this paper several approaches to fabricate semiconductor magnetic nanocomposite are reported. Several thiol- and amino- silane cross linked molecules were used to couple and embed CdSe and Fe3O4 nanoparticles into silica particles. The resulting nanocomposites were characterized by optical spectroscopies, transmission electron microscopy, electron paramagnetic spectroscopy and fluorescence optical microscopy. The new developed nanocomposite particles posses the advantage of being both magnetic and luminescent. The chemical functionality rich surface of these new nanoparticles could enable their application in bioassays, cell separation and drug delivery.
This paper describes the development of novel particle-based fluorescence resonance energy transfer (FRET) biosensors. It describes the fundamentals of FRET in heterogeneous systems and the application of the new sensors in monitoring the binding affinity of carbohydrates and glycoproteins to lectins, which are carbohydrate binding proteins. The sensing approach is based on FRET between fluorescein (donor) labeled lectin molecules, adsorbed on the surface of micrometric polymeric beads, and polymeric dextran molecules labeled with Texas Red (acceptor). The FRET signal of the sensor decreases in the presence of carbohydrates or glycoproteins that inhibit the binding of Texas Red-labeled dextran molecules to the lectinic binding sites. The new FRET sensors could discriminate between carbohydrates and glycoproteins based on their binding affinity to the FRET sensing particles. Thery were also used for quantitative analysis of carbohydrates and glycoproteins in aqueous samples.
This paper describes the synthesis and characterization of submicron phospholipid coated polystyrene particles, named lipobeads, with pH sensing capability. The phospholipids used to coat the particles are labeled with fluorescein and tetramethylrhodamine, which serves as a referencing fluorophore for increased accuracy of the pH measurements. The synthesis of the pH sensing lipobeads is realized by the covalent attachment of the fluorescent phospholipids to the surface of styrene-divinylbenzene micron or submicron sized particles. The pH dynamic range of the sensing particles is between pH 5.5 and 7 with a sensitivity of 0.1 pH units and they are photostable under the experimental conditions used in these studies. The fluorescent lipobeads are used to monitor pH changes in volume limited samples and to measure the pH of single macrophages. The lipobeads are ingested by the macrophages and directed to lysosomes, which are the cellular organelles involved in the phagocytosis process. Despite the high lyososomal levels of digestive enzymes and acidity, the absorbed particles remain stable for 6 hours in the cells when the cells are stored in a PBS buffer solution at pH 7.4.
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