Abstract
AbstractA novel bio-sensing platform is introduced by combination of a) geometrically controlled DNA bonding using vertically aligned diamond nano-wires and b) the superior electrochemical sensing properties of diamond as transducer material. Ultra-hard vertically aligned diamond nanowires are electrochemically modified to bond phenyl linker-molecules to their tips which provide mesospacing for DNA molecules on the transducer. The nano-wires are generated by reactive ion etching of metallically boron doped atomically smooth single crystalline CVD diamond. Surface properties are characterized by atomic force, scanning electron and scanning tunneling microcopy. Electro- and biochemical sensor properties are investigated using cyclic and differential pulse voltammetry as well as impedance spectroscopy with Fe(CN)63-/4- as redox mediators which reveal sensitivities of 2 pM on 3 mm2 sensor areas and superior DNA bonding stability over 30 hybridization/denaturation cycles. The fabrication of "all diamond" ultra-micro-electrode (UME) arrays and multi-gene sensors are discussed taking into account the unique properties of diamond.
Highlights
Nano-wires are new materials, which have characteristics with sometimes extraordinary mechanical, electrical, thermal and multifunctional properties.[1,2] By creating nanostructures; it is possible to control the fundamental properties of materials without change of chemical composition
Diamond nano-particles which trend to form clusters are dissolved in water by ultra-sonification (200 W, 20 kHz, 12 h) to form a pseudo-stable suspension.[38]. The concentration of this suspension is crucial and pretreatment of diamond powder is affecting the stability of the suspension
To realize from ultra-hard diamond nano-wires over an area of 3 mm2 we firstly grow atomically smooth metallically boron doped (p-type) diamonds by homoepitaxy on 1b diamond substrates by use of a micro-wave assisted chemical vapor deposition technique.[35,36]
Summary
Nano-wires are new materials, which have characteristics with sometimes extraordinary mechanical, electrical, thermal and multifunctional properties.[1,2] By creating nanostructures; it is possible to control the fundamental properties of materials without change of chemical composition. [33] In 2008, Zou et al [34] reported about the fabrication of nanopilar arrays using self aligned Au nanodots as etching mask in a bias-assisted reactive ion etching, applying a hydrogen/argon plasma These achievements demonstrate that vertically aligned diamond nano-wires can be fabricated by a variety of methods, no applications in electro- or bio-chemistry have up to now been reported. Such functionalized nano-wires are used to bond geometrically controlled oligonucleotide molecules to diamond, thereby combining the outstanding electrochemical properties of diamond as transducer with the advantages coming by dispersed and controlled bonding “like in aqueous solution” of DNA molecules Sensing properties of this new gene-sensor platform are characterized in detail with respect to sensitivity and chemical stability using cyclic (CV) and differential pulse voltammetry (DPV), and impedance spectroscopy (IMP). Ultra-micro electrode (UME) arrays from diamond will be introduced, which are extremely robust and suitable for applications in high through-put systems for gene sensing in clinical environments
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