DNA Bonding to CVD Diamond Probed by Scanning Electron-, Fluorescence-, and Atomic force- Microscopy
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0956-J09-09
DNA Bonding to CVD Diamond Probed by Scanning Electron-, Fluorescence-, and Atomic force- Microscopy Christoph E. Nebel1, Hiroshi Uetsuka1, Buhuslav Rezek2, Dongchan Shin1, Norio Tokuda3, and Takako Nakamura4 1 AIST, Diamond Research Center, Central 2, 1-1-1, Tsukuba, 305-8568, Japan 2 Institute of Physics, Cukrovarnicka 10, Praha, 162 53, Czech Republic 3 AIST, Nanotechnology Research Institute, Central 2-13, 1-1-1, Tsukuba, 305-8568, Japan 4 AIST, Center for Advanced Carbon Material, Central 2, Tsukuba, 305-8568, Japan ABSTRACT Double stranded desoxyribonucleic acid (ds-DNA) layers, bonded to hydrogen terminated polycrystalline diamond, are characterized by scanning electron (SEM), fluorescence (FM), and atomic force microscopy (AFM). DNA grafting has been achieved using photochemical bonding of ω-unsaturated 10-amino-dec-1-ene molecules. SEM detects local variations of electron affinities on polycrystalline diamond, revealing distinct grain structures. FM applied on fluorescence labeled ds-DNA show laterally varying intensities of typically 20 %, which resembles also grain structure as detected by SEM. Contact and tapping mode AFM characterization reveal a tilted DNA bonding to diamond, dense layer formation which gives rise to smoothening of surface properties. The lateral density variation of DNA is attributed to local variations of the photo-electron emission efficiency which affects the photochemical attachment chemistry of amine linker molecules to diamond. INTRODUCTION Bioelectronics is a rapidly progressing field at the junction of physics and biochemistry. The basic feature of bio-electronic devices is the immobilization of a biomaterial onto a transducer and the electronic detection of biological functions associated with the biological matrices. The growing use of deoxyribonucleic acid (DNA) micro-arrays and DNA chips in genetics, medicine and drug discovery shifted significant attention towards the realization of miniaturized and fast analytical systems [1-4]. DNA immobilization techniques have been explored for a variety of substrates like gold, carbon electrodes, and SiOx, to name a few [5-7]. These substrates show different characteristics with respect to flatness, homogeneity, availability and are also very different in chemical stability, reproducibility and biochemical manipulation. For active electronic bio-applications, the integration of bio-functionalized surfaces with microelectronics and micro-mechanical tools is required, which shifted activities towards chemical and biological modifications of semiconductors [8-11]. Most of the microelectronic-compatible materials like silicon, SiOx, and gold show, however, degradation of the interfaces which inhibits the development of integrated sensors [11]. Diamond is a promising candidate for bio-electronic devices as it shows good electronic and chemical properties, is considered to be biocompatible and can be grown single-, poly- or nanocrystalline, either by homo-epitaxy or by heteroepitaxy on a variety of substrates. Since it has bee
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