In this work we perform correlated structural and optical studies of single nanoparticles as well as explore the generality
of SMSERS. First, wide-field plasmon resonance microscopy is used to simultaneously determine the LSPR spectra of
multiple Ag nanoprisms, whose structure is determined using TEM. Next, the structure-property relationships for well-defined
and easily-controlled nanoparticle structures (e.g. monomers, dimers, and trimers) are studied using correlated
TEM, LSPR, and SERS measurements of individual SERS nanotags. We present the SER spectrum of reporter
molecules on a single nanotag comprised of a Au trimer. It was determined that of 40 individual nanotags, just 19
exhibited SERS. The remaining nanoparticles were established by TEM to be monomers. These results demonstrate that
SERS signal is observed from individual nanotags containing a junction or hot spot. Lastly, we explore crystal violet, a
triphenyl methane dye that was used in the seminal SMSERS investigations, and re-examine single-molecule sensitivity
using the isotopologue approach.
Detection tags based upon surface enhanced Raman scattering provide an alternative to the widely used fluorescence methods. Several aspects of these tags are presented in this report. The tags can be made to display many different spectra, thus they can be used for multiplexed detection schemes. They generate a large enough number of photons to be readily detected, and spectra acquired from mixtures of tags can be analyzed giving accurate amounts of the components. The surface of the tags can be easily modified to present common biological molecules (streptavidin and analogues). Finally, we demonstrate their use to quantitatively detect interleukin-4 (IL4) and interleukin-7 (IL7) in a microarray format.
In recent years there has been a great deal of interest in the measurement of DNA hybridization at surfaces. Surface-confined DNA hybridization has been used to monitor gene expression, to detect the presence of a particular DNA sequence and determine single nucleotide polymorphisms (SNPs). DNA microarrays, which can contain thousands of discrete DNA sequences on a single surface, have become widely used for hybridization studies. While a powerful technique, this technology is limited by the stability of the fluorescent dyes used to label the DNA, and the need to perform measurements ex-situ to reduce the fluorescence background. In this report, we describe the use of colloid-amplified surface plasmon resonance (SPR) to measure DNA hybridization at surfaces. SPR is a surface sensitive technique, which can be used to study hybridization in situ, and the use of colloidal metal tags provides excellent sensitivity. Angle-scanning SPR has been used to study oligonucleotide hybridization to surface confined probes, and work is underway to apply SPR imaging to study DNA hybridization in macro- and microarray formats.
The local structure of biological membranes is critically important to membrane function. Regions of very high positive and negative curvature are found in the membranes of many cells, and rapid changes in membrane curvature are integral parts of many cell activities (e.g. endo/exocytosis, cell crawling, cell division). Our goal is to understand the effects of changes in local membrane structure on membrane properties. Optical tweezers are used to control the local structure of the lipid bilayer by controlling the curvature of the membrane. We use giant (`cell-sized'), thin-walled vesicles as our membrane models. Optically trapped latex microspheres are used to deform the liposome bilayer, forming large areas of altered membrane curvature. In contrast to literature reports in which 514.5 nm light was used in optical trapping, we have not observed adhesion of uncoated latex microspheres to liposome vesicles, nor have we observed signs of rapidly increased osmotic pressure within irradiated vesicles. This indicates that the longer wavelength used in our studies (647.1 nm) is less damaging to biological membranes. Furthermore, optical trapping of vesicles with coexisting gel and fluid phase lipids did not lead to gross changes in domain structure, which would be expected upon laser-induced heating of the membrane.
Conference Committee Involvement (2)
Optical Methods in Drug Discovery and Development II
1 October 2006 | Boston, Massachusetts, United States
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.