Biomedical subjects

Carly S Levin

Publications and source records attributed to Carly S Levin.

5 recordsLinked to original sources

PubMed2006

In vivo detection of gold-imidazole self-assembly complexes: NIR-SERS signal reporters.

Here we report in vitro and in vivo detection of self-assembled Au-imidazole by using near-infrared surface-enhanced Raman scattering (NIR-SERS). In vivo, the Au-imidazole structures were administered into tumor-bearing mice and detected noninvasively. The self-assembled Au-imidazole complexes were generated by the adsorption of imidazole molecules onto Au nanoparticles (NP) and were then characterized as aqueous suspensions by using NIR-SERS, angle-dependent light scattering with fractal dimension analysis, and visible extinction spectroscopy. The structure and optical activity was sensitive to imidazole concentration and Au NP size. Specifically, the Au-imidazole assemblies formed at lower imidazole concentrations had the lowest fractal dimension (D(f) = 1.2) and the largest Raman enhancement factors for the dominant NIR-SERS feature, a ring-breathing vibrational mode at 954 cm(-1). Changes in elastic scattering intensity, fractal dimension, and surface plasmon absorption were observed with increasing imidazole concentration. The Raman enhancement factor was also found to range between 10(6) and 10(9) with different primary Au nanoparticle sizes. For the higher enhancement factor systems, NIR-SERS detection of Au-imidazole was performed with data acquisitions time of only 5 s. The largest enhancement was observed for the 954-cm(-1) feature at an imidazole concentration of 1.9 microM when coupled to 54-nm-diameter Au NPs (the largest NP tested). Finally, we show the first demonstration of in vivo, noninvasive, and real-time SERS detection.

Animals↗

PubMed2006

Determining the conformation of thiolated poly(ethylene glycol) on Au nanoshells by surface-enhanced Raman scattering spectroscopic assay.

The packing density of thiolated poly(ethylene glycol) (PEG) adsorbates on Au nanoshells is determined by exploiting the surface-enhanced Raman scattering response of individual nanoshell substrates. By incorporating the linker molecule p-mercaptoaniline (pMA), the number of 2000 MW and 5000 MW PEG molecules on each nanoparticle is determined by interpolation of the Langmuir isotherm for pMA. We conclude that both PEG adsorbates maintain a compact "brush" rather than an extended "mushroom" configuration on nanoshell surfaces.

Gold↗

PubMed2006

All-optical nanoscale pH meter.

We show that an Au nanoshell with a pH-sensitive molecular adsorbate functions as a standalone, all-optical nanoscale pH meter that monitors its local environment through the pH-dependent surface-enhanced Raman scattering (SERS) spectra of the adsorbate molecules. Moreover, we also show how the performance of such a functional nanodevice can be assessed quantitatively. The complex spectral output is reduced to a simple device characteristic by application of a locally linear manifold approximation algorithm. The average accuracy of the nano-"meter" was found to be +/-0.10 pH units across its operating range.

Equipment Design↗

PubMed2006

Chain-length-dependent vibrational resonances in alkanethiol self-assembled monolayers observed on plasmonic nanoparticle substrates.

Alkanethiol self-assembled monolayers (SAMs) on gold exhibit a series of sharp resonances in their surface-enhanced Raman spectrum that depend dramatically on carbon chain length. This unusual behavior suggests a coupling of the gold-sulfur bond stretch with the longitudinal acoustic, "accordion", vibrations of the molecular alkane chain. A simple model of a one-dimensional chain attached to a surface quantitatively reproduces these previously unreported experimental observations in this important nanomaterial system.

Alkanes↗

PubMed2005

Nanosphere arrays with controlled sub-10-nm gaps as surface-enhanced raman spectroscopy substrates.

We demonstrate a convenient and cost-effective chemical approach for fabricating highly ordered Au nanoparticle arrays with sub-10-nm interparticle gaps. Near-field enhancements inside the interparticle gaps create uniform periodic arrays of well-defined "hot spots" exploitable for large surface-enhanced Raman spectroscopy (SERS) enhancements. A cetyltrimethylammonium bromide (CTAB) bilayer surrounding each individual nanoparticle upon array crystallization is responsible for this periodic gap structure; displacement of the CTAB by smaller thiolated molecules does not affect the structural integrity of the arrays. As SERS substrates, the as-fabricated Au nanoparticle arrays exhibit high SERS sensitivity, long-term stability, and consistent reproducibility.

Journal Article↗