Microscopic diagnostics of DNA molecules on mono-crystalline diamond

Detailed data about deoxyribonucleic acid (DNA) attachment, arrangement, density and functionality on mono-crystalline diamond surfaces are obtained by direct measurements in electrolytic solutions using fluorescence microscopy and atomic force microscopy in various regimes (oscillating, contact, phase, and surface potential imaging) and by fitting the data into a microscopic geometrical model of DNA. DNA is immobilized on undoped and boron-doped diamonds with hydrogen and oxygen surface terminations which were functionalized by aminodecene and nitrofenyl linker molecules. The data show that, except photochemically processed oxidized diamond surfaces, the DNA molecules are covalently linked to diamond in a 65-92 angstrom thin and highly dense layers (6 x 10(12) molecules/cm(2)) with sub-nanometer intermolecular spacing and a strong tilt of 31 degrees with respect to the surface. Ordering of these DNA layers shows only a weak (< 10%) response to a change of buffer salinity in the range of 1-300 mM. The data are discussed with view to biosensor applications. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.