Mechanistic Investigation into the Effect of Different DNA Sequences on the Shape and Morphology of Nanoparticles
The use of programmed DNA oligomers on the growth of gold nanoprisms has resulted in interesting shapes such as rough round, six-pointed star, hexagon and smooth round shapes respectively, for A, T, G and C. Despite the interesting finding, the mechanism of DNA mediated growth remains unclear. Our goal in this work focuses on elucidating the role of DNA using spectroscopic and microscopic characterization of particle growth kinetics. Using oligomers of thymine, the seed nanoprism grew into six point stars. The shape was observed to proceed through intermediates- from a prism, to a round polyhedron, to a hexagon and finally into a six pointed star. The intermediates observed from this growth were observed with other bases as well. Round polyhedron shapes were observed for polyadenine and polycytosine, and hexagon shapes for polyguanine. The extent of growth formed using different bases was found to be correlated to the trend of binding affinity of the bases to gold surfaces (A>C>G>T). This hypothesis is supported using zeta potential and fluorescence assays to quantify the DNA on the nanoparticles. The role of DNA binding to the nanoprism seed and the gold precursor in guiding the nanoparticle growth is proposed. The relationship between the amount of DNA and gold precursor used for the growth was also determined.
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