Publications (4) View all
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Article: Fabrication and characterization of multimodal magnetic-fluorescent polystyrene nanowires as selective cell imaging probes
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ABSTRACT: The work presented here describes the preparation of new fluorescent, magnetic polystyrene (PS) nanowires via vacuum assisted infiltration of porous anodised aluminium oxide (AAO) membranes. A polymer solution of high molecular weight PS in THF, superparamagnetic magnetite nanoparticles and coumarin-153 dye is used to create the nanowires (NW) within the 200 nm diameter membranes. NW released by membrane dissolution have a high aspect ratio and a curled 'bamboo' like structure to them. NW have been characterised by optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). These wires were strongly luminescent and show good response to an external magnetic field. VSM measurements of these samples have shown presence of both superparamagnetic (SPM) and non-superparamagnetic components. The biological application potential of NW was also investigated by functionalising them with primary and secondary antibodies and incubation with epithelial lung cancer cells (A549 cell line). NW showed binding affinity to the surface of the cells and also endocytotic internalisation in the case of short wires. These structures have good potential for use in bio-medical imaging and diagnostic applications due to their additional modalities linked to their intrinsic material properties.Journal of Materials Chemistry. 21(37):14219-14225. -
Article: Queuosine Deficiency in Eukaryotes Compromises Tyrosine Production through Increased Tetrahydrobiopterin Oxidation
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ABSTRACT: Queuosine is a modified pyrrolopyrimidine nucleoside found in the anticodon loop of transfer RNA acceptors for the amino acids tyrosine, asparagine, aspartic acid, and histidine. Because it is exclusively synthesized by bacteria, higher eukaryotes must salvage queuosine or its nucleobase queuine from food and the gut microflora. Previously, animals made deficient in queuine died within 18 days of withdrawing tyrosine, a nonessential amino acid, from the diet (Marks, T., and Farkas, W. R. (1997) Biochem. Biophys. Res. Commun. 230, 233-237). Here, we show that human HepG2 cells deficient in queuine and mice made deficient in queuosine-modified transfer RNA, by disruption of the tRNA guanine transglycosylase enzyme, are compromised in their ability to produce tyrosine from phenylalanine. This has similarities to the disease phenylketonuria, which arises from mutation in the enzyme phenylalanine hydroxylase or from a decrease in the supply of its cofactor tetrahydrobiopterin (BH4). Immunoblot and kinetic analysis of liver from tRNA guanine transglycosylase-deficient animals indicates normal expression and activity of phenylalanine hydroxylase. By contrast, BH4 levels are significantly decreased in the plasma, and both plasma and urine show a clear elevation in dihydrobiopterin, an oxidation product of BH4, despite normal activity of the salvage enzyme dihydrofolate reductase. Our data suggest that queuosine modification limits BH4 oxidation in vivo and thereby potentially impacts on numerous physiological processes in eukaryotes.Journal of Biological Chemistry. 286(22):19354-19363. -
Article: CdTe Quantum Dot/Dye Hybrid System as Photosensitizer for Photodynamic Therapy
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ABSTRACT: We have studied the photodynamic properties of novel CdTe quantum dots-methylene blue hybrid photosensitizer. Absorption spectroscopy, photoluminescence spectroscopy, and fluorescence lifetime imaging of this system reveal efficient charge transfer between nanocrystals and the methylene blue dye. Near-infrared photoluminescence measurements provide evidence for an increased efficiency of singlet oxygen production by the methylene blue dye. In vitro studies on the growth of HepG2 and HeLa cancerous cells were also performed, they point toward an improvement in the cell kill efficiency for the methylene blue-semiconductor nanocrystals hybrid system.Nanoscale Research Letters 03/2010; 5(4):753-760. · 2.73 Impact Factor -
Article: Photosensitizer Methylene Blue-Semiconductor Nanocrystals Hybrid System for Photodynamic Therapy
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ABSTRACT: In this work we report on the development of novel hybrid material with enhanced photodynamic properties based on methylene blue and CdTe nanocrystals. Absorption spectroscopy, visible photoluminescence spectroscopy and fluorescence lifetime imaging of this system reveal efficient charge transfer between nanocrystals and the methylene blue dye. Near infra-red photoluminescence measurements provide evidence for an increased efficiency of singlet oxygen production by the methylene blue dye. In vitro studies on the growth of HepG2 and HeLa cancerous cells were also performed, they point towards an improvement in the cell kill efficiency for the methylene blue-semiconductor nanocrystals hybrid system.Journal of Nanoscience and Nanotechnology. 10(4):2656-2662.
