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Online ISSN 1751-875X Print ISSN 1751-8741

IET Nanobiotechnology

Volume 2, Issue 2, June 2008

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Volume 2, Issue 2

June 2008

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    • Dielectrophoretic assembly of insulinoma cells and fluorescent nanosensors into three-dimensional pseudo-islet constructs
      • Author(s): R. Pethig ; A. Menachery ; E. Heart ; R.H. Sanger ; P.J.S. Smith
      • Source: IET Nanobiotechnology, Volume 2, Issue 2, p. 31 –38
      • DOI:  10.1049/iet-nbt:20070027
      • Type: Article
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      • p. 31 –38 (8)
        Dielectrophoretic forces, generated by radio-frequency voltages applied to micromachined, transparent, indium tin oxide electrodes, have been used to condense suspensions of insulinoma cells (BETA-TC-6 and INS-1) into a 10×10 array of three-dimensional cell constructs. Some of these constructs, measuring ∼150 µm in diameter, 120 µm in height and containing around 1000 cells, were of the same size and cell density as a typical islet of Langerhans. With the dielectrophoretic force maintained, these engineered cell constructs were able to withstand mechanical shock and fluid flow forces. Reproducibility of the process required knowledge of cellular dielectric properties, in terms of membrane capacitance and membrane conductance, which were obtained by electrorotation measurements. The ability to incorporate fluorescent nanosensors, as probes of cellular oxygen and pH levels, into these ‘pseudo-islets’ was also demonstrated. The footprint of the 10×10 array of cell constructs was compatible with that of a 1536 microtitre plate, and thus amenable to optical interrogation using automated plate reading equipment.
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      Enhanced bio-molecular interactions through recirculating microflows
      • Author(s): A. Chandrasekaran  and  M. Packirisamy
      • Source: IET Nanobiotechnology, Volume 2, Issue 2, p. 39 –46
      • DOI:  10.1049/iet-nbt:20070029
      • Type: Article
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      • p. 39 –46 (8)
        A recirculating microfluidic platform has been developed for carrying out optical bio-detection. The present device can be used for passive mixing of the biological species with the microfluidic channel without immobilisation, through appropriate design and flow control. The feasibility of bio-detection using the present setup has been demonstrated through the method of fluorescence and the experiments were carried out with Antisheep Antibody (AB) tagged with Alexafluor 647 (AF647) fluorophore particles. By controlling the fluid flow, it was possible to isolate AB separately into a recirculation zone within the microfluidic channel, thereby enabling qualitative and quantitative bio-detection. Finite element modelling of the flow behaviour has been carried out and the results were similar to the results of flow visualisation obtained with tagged antibody particles. The present work thus provides confidence in using the hybrid integrated device for in situ rapid biomedical detection of biological pairs or individual specimen in fluorescence-based chemical and biological sensing.
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      Fluorescent resonance energy transfer based detection of biological contaminants through hybrid quantum dot–quencher interactions
      • Author(s): D. Ramadurai ; E. Norton ; J. Hale ; J.W. Garland ; L.D. Stephenson ; M.A. Stroscio ; S. Sivananthan ; A. Kumar
      • Source: IET Nanobiotechnology, Volume 2, Issue 2, p. 47 –53
      • DOI:  10.1049/iet-nbt:20070033
      • Type: Article
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      • p. 47 –53 (7)
        A nanoscale sensor employing fluorescent resonance energy transfer interactions between fluorescent quantum dots (QDs) and organic quencher molecules can be used for the multiplexed detection of biological antigens in solution. Detection occurs when the antigens to be detected displace quencher-labelled inactivated (or dead) antigens of the same type attached to QD–antibody complexes through equilibrium reactions. This unquenches the QDs, allowing detection to take place through the observation of photoluminescence in solution or through the fluorescence imaging of unquenched QD complexes trapped on filter surfaces. Multiplexing can be accomplished by using several different sizes of QDs, with each size QD labelled with an antibody for a different antigen, providing the ability to detect several types of antigens or biological contaminants simultaneously in near real-time with high specificity and sensitivity.
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