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Principles and Methods of Nanoassembly Based DNA Amplified Sensor Detection

Author: MaWei
Tutor: ZuoChuanLai
School: Jiangnan University
Course: Food Nutrition and Safety
Keywords: Gold nanorod Gold nanostar Magnetic nanoparticles Polymerase chainreaction Plasmonic Circular Dichroism Surface enhanced Raman scattering Magneticresonance switch
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Type: PhD thesis
Year: 2013
Downloads: 217
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Abstract


Chiral nanoscale photonic systems typically follow either tetrahedral or helicalgeometries that require four or more different constituent nanoparticles. Smaller number ofparticles and different chiral geometries taking advantage of the self-organization capabilitiesof nanomaterials will advance understanding of chiral plasmonic effects, facilitatedevelopment of their theory, and stimulate practical applications of chiroplasmonics. Herewe show that gold nanorods self-assemble into side-by-side orientated pairs and “ladders” inwhich chiral properties originate from the small dihedral angle between them. Spontaneoustwisting of one nanorod versus the other one breaks the centrosymmetric nature of the parallelassemblies. Two possible enantiomeric conformations with positive and negative dihedralangles were obtained with different assembly triggers. The chiral nature of the anglednanorod pairs was confirmed by4π full space simulations and the first example ofsingle-particle CD spectroscopy.Plasmonic NR assemblies showed geometry-dependent optical properties that originatedfrom the collective interactions of the individual monomers shapes. Although signifcantprogress has been achieved in the self-assembly of GNR, the assembly of GNR in a controlledmanner yielding strong optical signal for applications remains a challenge. By changing thesurface chemistry of the nanorods, we have been able to organize GNRs based on PCR withETE and SBS patterns. For SBS assemblies, the collective plasmon interaction gives rise tounique chirooptical properties, exhibiting good agreement with model simulations.Comparably, our GNR assemblies (ETE and SBS) can also be used for the preparation ofRaman-active nanostructures with strong SERS properties. The results herein show that ourassembly strategies may be used to develop novel, ultrasensitive chirality-based sensors andSERS sensors with limits of detection (LOD) of3.73aM,1.14aM (SBS by SERS) and1.58fM (ETE by SERS), respectively. This approach provides a new route to the organization ofanisotropic nanoparticles.The seed growth method will be used for controllable synthesis of gold nanostar material.Through stablization and modification technology, a self-assembled nanostar dimer based onthe Hg2+-mediated T–Tbase pair of ssDNA will be investigated. By controlling the parametersof DNA concentration, stable and high yield of gold nanostar dimer materials were prepared,which had enhanced hot spot in the dimer gap and can be used as strong plasmonic Ramanenhancement material. Through structural characterization and spectroscopic properties study,we shall investigate assembly and the optical properties of dimer made differrent size goldnanostar. Finally, the fabricated gold nanostar dimer has been developed as a SERS sensor forHg2+detection. The enormous enhancement of the electromagnetic field by the dimerstructures facilitates extraordinary SERS intensity. The LOD is0.8pg/mL and the linear rangeis0.002to1ng/mL.The assembly of magnetic nanoparticle represents another type of assembly withinteresting collective magnetic interaction. Magnetic relaxation switch difference fromdispersed and assembled state of magnetic NPs can be employed for sensors. Through modification techniques, the surface functional group on the magnetic nanoparticles will beconjugated forward and reverse primers, respectively. The high performance magneticnanoprobe will be obtained. Based on the prepared nanoprobe, the controlable magneticnanoparticle assembly by parameters of cycles and starting DNA concentration will beinvestigated. At the same time, the magnetic nanoparticle assembly can also be used asmagnetic resonance nanoprobe with magnetic resonance relaxation properties. The magneticresonance relaxation sensor for DNA detection will be fabricated. Thanks to highamplification efficiency of PCR, the established method was ultrasensitive with LOD of4.26aM with a wide range of target DNA from0.01fM to10000fM.A simple and ultrasensitive method was developed for the detection of Ochratoxin A,utilizing an aptamer as a molecular recognition probe and RT-qPCR amplification of itscomplementary DNA as signal generators. Under the optimized conditions, the Ct increasedlinearly with10-fold serial dilutions of OTA from5×10-6to5ng/mL, with a LOD of1fg/mL.The specificity of this aptasensor was considered to be excellent, as when tested against fourother toxins it produced no obvious Ct value change. Furthermore, a satisfactory analyteconcentration recovery with recovery in the range of99–112%was obtained from a series ofconcentrations of OTA spiked into red wine. Therefore, this highly sensitive approach shows asignificant potential in a wide range of target analytes.

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