Spectroscopic studies of nucleic acid additions during seed-mediated growth of gold nanoparticles
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Patrick Dennis and Rajesh R. Naik Materials & Manufacturing Directorate, Soft Matter Materials Branch, Air Force Research Laboratory, Wright Patterson AFB, Ohio 45433, USA
Valeria T. Milama) School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, USA; Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, USA; and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, USA (Received 16 July 2014; accepted 9 November 2014)
The effect of adding nucleic acids to gold seeds during the growth stage of either nanospheres or nanorods was investigated using UV–Vis spectroscopy to reveal any oligonucleotide base or structure-specific effects on nanoparticle growth kinetics or plasmonic signatures. Spectral data indicate that the presence of DNA duplexes during seed aging drastically accelerated nanosphere growth while the addition of single-stranded polyadenine at any point during seed aging induces nanosphere aggregation. For seeds added to a gold nanorod growth solution, single-stranded polythymine induces a modest blue shift in the longitudinal peak wave length. Moreover, a particular sequence comprised of 50% thymine bases was found to induce a faster, more dramatic blue shift in the longitudinal peak wave length compared to any of the homopolymer incubation cases. Monomeric forms of the nucleic acids, however, do not yield discernable spectral differences in any of the gold suspensions studied.
I. INTRODUCTION
Gold nanoparticles (AuNPs) have been heavily investigated for their unique size- and shape-dependent optical properties. These effects are apparent in the variation of optical spectra that AuNPs exhibit for different sizes and shapes ranging from spheres (plasmon band at ;520 nm) to nanorods (transverse and longitudinal plasmon bands at ;520 and 600–1600 nm, respectively).1–3 These signature spectral bands correspond to a localized surface plasmon resonance effect caused by the coherent, collective oscillation of conduction band electrons in AuNPs illuminated with light.1 In addition to the effects of size and shape on the resulting absorption and scattering of light, changes in the spatial arrangement of AuNPs can shift the position of the plasmon bands.4–9 AuNP surfaces can be conveniently modified to incorporate other moieties such as oligonucleotides, proteins, and antibodies due to the strong binding interaction between gold and chemical moieties such as thiols.7,10–13 As a result of these practical optical properties and conjugation Contributing Editor: Sanjay Mathur a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.409 666
J. Mater. Res., Vol. 30, No. 5, Mar 14, 2015
http://journals.cambridge.org
Downloaded: 19 Mar 2015
possibilities, AuNPs have been studied in biosensing, molecular imaging, therapeutic, and medical diagnostic applications.6,12,14 Synthesis of AuNPs of various
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