Nanoparticle Bridge DNA Biosensor

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dc.contributor Huang , Hong -Wen en_US
dc.date.accessioned 2010 -07 -19T19 :55 :06Z
dc.date.accessioned 2011 -08 -24T21 :43 :54Z
dc.date.available 2010 -07 -19T19 :55 :06Z
dc.date.available 2011 -08 -24T21 :43 :54Z
dc.date.issued 2010 -07 -19
dc.date.submitted January 2010 en_US
dc.identifier.uri http : / /hdl .handle .net /10106 /4953
dc.description.abstract A new DNA sensing method is demonstrated in which DNA hybridization events lead to the formation of nanoparticle satellites that bridge two electrodes and are detected electrically . The hybridization events are exclusively carried out only on specific locations , the surfaces of C -ssDNA modified 50 nm GNPs . The uniqueness of this work is that only a small number of T -ccDNA molecules ( <10 ) is required to form the nanoparticle satellites , allowing ultra -sensitive DNA sensing . The principle of this new DNA sensing technique has been demonstrated using target DNA and three -base -pair -mismatched DNA in 20nM concentrations . Three single -stranded DNA (ssDNA ) system is used in our experiment which includes Capture -ssDNA (C -ssDNA ) , Target -ssDNA (T -ssDNA ) and Probe -ssDNA (P -ssDNA ) . Both C -ssDNA and P -ssDNA are modified by a thiol group and can hybridize with different portions of T -ssDNA . T -ssDNA requires no modification in three ssDNA system , which is beneficial in many applications . C -ssDNA modified 50nm gold nanoparticle (C -50au ) and P -ssDNA modified 30nm gold nanoparticle (P -30au ) are prepared through the reaction of thiol -gold chemical bonding between thiolated ssDNA and gold nanoparticle (GNP ) (C -ssDNA with 50nm GNP , P -ssDNA with 30nm GNP ) . We controllably place the C -50au only on the SiO₂ band surface ( ~ 90nm width ) between two gold electrodes (source and drain electrodes ) by forming positively - and negatively -charged self -assembled monolayers (SAMs ) on SiO₂ and gold surface , respectively . DNA modified GNP is negatively charged due to ionization of phosphate group on DNA back bone . C -50au therefore is negatively charged and can only be attracted toward SiO₂ area (repelled by negatively charged gold electrode surface ) . The amine group of positively -charged SAMs on SiO₂ surface is then passivated by converting to non -polar methyl functional group after C -50au placement . P -30au is first hybridized with T -ssDNA in the solution phase (T -P -30au formed ) and is introduced into DNA detection device in which C -50au are immobilized on ~90nm width SiO₂ band (between two gold electrodes ) . The passivation step ensures every T -P -30au are attached only to C -50au through hybridization (T -P -30au will not be attracted toward SiO₂ surface or gold electrodes ) . GNP bridges are formed across the electrodes and provide an electrical path between two gold electrodes .We ensure that every T -P -30au only hybridizes on the surface of C -50au by (1 ) accurately controlling C -50au placement between two gold electrodes , (2 ) passivating positively -charged SAMs on SiO₂ surface after C -50au immobilization . When T -P -30au hybridize with C -50au on ~90nm wide SiO₂ surface , GNP bridges form and provide an electrical path between two gold electrodes even with only a few hybridization events . Experimental results show that even a few GNP bridges formed on SiO₂ band can provide a significant conductance change from an open circuit to a conductive circuit (current = 0 .5 uA at voltage = 0 .1 V with four GNP bridge ) . We also used 3 -base -pair -mismatched ssDNA (3mm -ssDNA ) as a control experiment , which always resulted in an open circuit (no GNP bridge formed ) . Our detection device is compatible with current CMOS fabrication technology and can be manufactured on a wafer scale . The direct electrical output of this DNA detection technique provides a promising basis for high -throughput screening (can be fabricated on a wafer scale ) with no expensive equipment required . en_US
dc.language.iso EN en_US
dc.publisher Materials Science & Engineering en_US
dc.title Nanoparticle Bridge DNA Biosensor en_US
dc.type Ph .D . en_US

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Nanoparticle Bridge DNA Biosensor. Available electronically from http : / /hdl .handle .net /10106 /4953 .

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