Site-Specific Attachment of Gold Nanoparticles to DNA Templates
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Site-Specific Attachment of Gold Nanoparticles to DNA Templates Karen A. Stevenson, Govindarajan Muralidharan, Leon Maya1, Jack C. Wells2, Jacob Barhen2, Thomas Thundat Life Sciences Division, 1 Chemical and Analytical Sciences Division, 2 Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831
ABSTRACT DNA was used as a scaffold for the binding of gold nanoparticles using a standard chemical technique. A DNA template was designed with amino-modified thymines located every 3.7 nm, which would allow the attachment of the carboxylic acid functionalized gold nanoparticles. The gold particles were covalently bound to the amino groups on the DNA using standard 1-ethyl-3(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) chemistry in the presence of a competitor to block excess gold binding sites. The products were analyzed by transmission electron microscopy (TEM) and atomic force microscopy (AFM).
INTRODUCTION The need to produce regular arrangements of nanoparticles led to the idea of using DNA as a scaffold or template for assembly of nanoscale arrays. Beginning in the 1980s Seeman et al. experimented with combining DNA fragments to produce geometrical shapes, including cubes [1], triangles [2], two-dimensional arrays [3-5] and various forms of DNA knots [6,7]. Using DNA as a structural molecule has many advantages. It can be easily synthesized in lengths from 5 to over 100 nucleotides. It can be joined end to end to produce longer linear molecules or more complex shapes, and it can be modified at predetermined sites to allow for the attachment of other molecules in a specific manner. The precise arrangement of nanoparticles to form an array is a difficult task. DNA has been used by others as a template for the attachment of particles. Mirkin et al. [8-10] and Alivisatos et al. [11,12] have successfully attached oligonucleotide derivatized nanoparticles to DNA using hybridization techniques. Niemeyer and coworkers have assembled biotinylated gold clusters on streptavidin-DNA oligonucleotides and subsequently hybridized the clusters to a complementary RNA template [13]. Cassell et al. assembled fullerene derivatives along the DNA backbone using cation exchange [14]. The present study was an attempt to use DNA as a scaffold for placement of gold nanoparticles at specific sites using a chemical reaction. Gold nanoparticles with an average diameter of 1.5 nm were synthesized with a mercaptosuccinic acid coating. Oligonucleotides were designed with amino-modified bases for attachment to carboxylic acid functionalized gold particles. The modified bases were separated by 10 base pairs (approximately 3.7 nm). The reaction between the amino group on the DNA and the carboxyl group on the gold particle was facilitated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and Nhydroxysuccinimide (NHS). Analysis of the products by transmission electron microscopy C4.2.1
(TEM), and atomic force microscopy (AFM) showed that the gold particles are bound to the DNA.
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