title: Direct optical detection of aptamer conformational changes induced by target molecules.
abstract: Aptamers are single-stranded DNA/RNA oligomers that fold into three-dimensional conformations in the presence of specific molecular targets. Surface-enhanced Raman spectroscopy (SERS) of thiol-bound DNA aptamer self-assembled monolayers on Au nanoshell surfaces provides a direct, label-free detection method for the interaction of DNA aptamers with target molecules. A spectral cross-correlation function, Gamma, is shown to be a useful metric to quantify complex changes in the SERS spectra resulting from conformational changes in the aptamer induced by target analytes. While the pristine, unexposed anti-PDGF (PDGF = platelet-derived growth factor) aptamer yields highly reproducible spectra with Gamma = 0.91 +/- 0.01, following incubation with PDGF, the reproducibility of the SERS spectra is dramatically reduced, yielding Gamma = 0.67 +/- 0.02. This approach also allows us to discriminate the response of a cocaine aptamer to its target from its weaker response to nonspecific analyte molecules.
authors.affiliation: Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, Texas 77005, USA.
authors.forename: Oara
authors.initials: O
authors.lastname: Neumann
authors.forename: Dongmao
authors.initials: D
authors.lastname: Zhang
authors.forename: Felicia
authors.initials: F
authors.lastname: Tam
authors.forename: Surbhi
authors.initials: S
authors.lastname: Lal
authors.forename: Pernilla
authors.initials: P
authors.lastname: Wittung-Stafshede
authors.forename: Naomi J
authors.initials: NJ
authors.lastname: Halas
mesh_terms: D052157:Aptamers, Nucleotide / Q000032:analysis*; D003042:Cocaine / Q000737:chemistry*; D006046:Gold / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry; D009690:Nucleic Acid Conformation; D010982:Platelet-Derived Growth Factor / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D013059:Spectrum Analysis, Raman; D013499:Surface Properties
chemical_list: D052157:Aptamers, Nucleotide; D010982:Platelet-Derived Growth Factor; D006046:Gold; D012822:Silicon Dioxide; D003042:Cocaine