Terminal phosphate group influence on DNA - TiO 2 nanoparticle interactions
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Terminal phosphate group influence on DNA - TiO2 nanoparticle interactions Zachary Rice1, Nathaniel C. Cady1, Magnus Bergkvist1 1 College of Nanoscale Science & Engineering University at Albany, Albany, New York, USA ABSTRACT Immobilization of DNA/RNA, onto various metal and metal oxide surfaces is of great importance for the development of future microarray, gene mapping, DNA sequencing, nanoparticle targeting, and sensor applications. Attachment of DNA to solid interfaces typically occurs through either electrostatic interactions or covalent bonds to functional groups introduced to nucleic acid termini. Previously, we and others have demonstrated that alkanephosphates and terminal phosphate groups present on nucleic acids play an important role in the interaction with group IV metal oxides such as zirconium and hafnium, providing a stable linkage to the surface. Titanium dioxide (TiO2), which is frequently employed in various nanoscale applications, belongs to the same group and similar interactions with phosphate are expected. Various adsorption studies have demonstrated binding of nucleic acids to TiO2 surfaces, although the influence of terminal phosphate versus electrostatic interaction (via the DNA/RNA backbone) on the surface interaction is unclear. The research presented here investigates the effect of nucleic acid length, presence of terminal phosphates, and differences between dsDNA and ssDNA on their binding to TiO2 nanoparticles. TiO2 nanoparticles (20 nm) were used to study the adsorption of Lambda DNA (~48 kbp), and shorter (21 bp) ssDNA and dsDNA oligonucleotides with and without a 5’ phosphate group. Initial adsorption of DNA to nanoparticles was calculated via UV absorption. Results showed that all types of nucleic acids (Lambda DNA, ssDNA and dsDNA) initially bind to nanoparticles, independent of molecular weight single/double strandedness, or phosphorylation state. The total amount of DNA initially adsorbed to nanoparticles (ng/particle) differs between ssDNA and dsDNA, as well as the length of the DNA used. These results show that nucleic acid interactions with TiO2 nanoparticles are not dependent upon the presence of a terminal phosphate group. These results provide valuable data for future applications based on DNA-nanoparticle constructs including nanoelectronics, photovoltaics, and biotemplated synthesis of semiconducting materials. INTRODUCTION Surface attachment of nucleic acids (DNA/RNA) is of interest for various applications including microarrays, gene mapping, and biosensors. Surface immobilization of nucleic acids can be realized through various methods. For example, DNA can interact with polymer surface coatings [1], adsorb onto surfaces via electrostatic interactions [2] or covalently be coupled to a surface [3]. A possible alternative approach for binding nucleic acids to solid supports is based on the strong interaction between phosphate/phosphonate groups and transition metal oxides. Organophosphonates have been shown to bind directly to zirconium and titanium dioxi
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