Label-free in situ detection of individual macromolecular assemblies by surface enhanced Raman scattering

Asiala, Steven M.; Schultz, Zachary D.

doi:10.1039/c2cc37268a

Cited by 21 publications

(39 citation statements)

References 20 publications

(34 reference statements)

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“…However, the limit of detection of 2-D substrates in solution is still controlled by transport, which can hinder analyte interaction with the SERS-active surface. 24 Over the years, methods have been developed to increase substrate-analyte interactions. Chemical modifications have been shown to increase affinity of the analyte molecules for the SERS substrate.…”

Section: Introductionmentioning

confidence: 99%

Ultrasensitive Surface-Enhanced Raman Scattering Flow Detector Using Hydrodynamic Focusing

et al. 2013

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Label-free, chemical specific detection in flow is important for high throughput characterization of analytes in applications such as flow injection analysis, electrophoresis, and chromatography. We have developed a surface-enhanced Raman scattering (SERS) flow detector capable of ultrasensitive optical detection on the millisecond time scale. The device employs hydrodynamic focusing to improve SERS detection in a flow channel where a sheath flow confines analyte molecules eluted from a fused silica capillary over a planar SERS-active substrate. Increased analyte interactions with the SERS substrate significantly improve detection sensitivity. The performance of this flow detector was investigated using a combination of finite element simulations, fluorescence imaging, and Raman experiments. Computational fluid dynamics based on finite element analysis was used to optimize the flow conditions. The modeling indicates that a number of factors, such as the capillary dimensions and the ratio of the sheath flow to analyte flow rates, are critical for obtaining optimal results. Sample confinement resulting from the flow dynamics was confirmed using wide-field fluorescence imaging of rhodamine 6G (R6G). Raman experiments at different sheath flow rates showed increased sensitivity compared with the modeling predictions, suggesting increased adsorption. Using a 50-millisecond acquisitions, a sheath flow rate of 180 μL/min, and a sample flow rate of 5 μL/min, a linear dynamic range from nanomolar to micromolar concentrations of R6G with a LOD of 1 nM is observed. At low analyte concentrations, rapid analyte desorption is observed, enabling repeated and high-throughput SERS detection. The flow detector offers substantial advantages over conventional SERS-based assays such as minimal sample volumes and high detection efficiency.

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Section: Introductionmentioning

confidence: 99%

Ultrasensitive Surface-Enhanced Raman Scattering Flow Detector Using Hydrodynamic Focusing

et al. 2013

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“…We previously showed a similar effect for the transient detection of lipid vesicles, where the interaction with the surface lasted on the order of 100 ms and signal acquisitions of several seconds did not provide detectable signals. 26 In Figure 2C, we observe that a clear spectrum can be obtained from DSERS analysis.…”

Section: Resultsmentioning

confidence: 82%

Sheath flow SERS for chemical profiling in urine

et al. 2016

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The molecular specificity and sensitivity of surface enhanced Raman scattering (SERS) makes it an attractive method for biomedical diagnostics. Here we present results demonstrating the utility and complications for SERS characterization in urine. The chemical fingerprint characteristic of Raman spectra suggests use as a label free diagnostic; however, the complex composition of biological fluids presents a tremendous challenge. In particular, the limited number of surface sites and competing absorption tend to mask the presence of analytes in solution, particularly when the solution contains multiple analytes. To address these problems and characterize biological fluids we have demonstrated a sheath-flow interface for SERS detection. This sheath-flow SERS interface uses hydrodynamic focusing to confine analyte molecules eluting out of a column onto a planar SERS substrate where the molecules are detected by their intrinsic SERS signal. In this report we compare direct detection of benzoylecgonine in urine using DSERS with chemical profiling by capillary zone electrophoresis and sheath-flow SERS detection. The SERS spectrum from the observed migration peaks can identify benzoylecgonine and other distinct spectra are also observed, suggesting improved chemical diagnostics in urine. With over 2000 reported compounds in urine, identification of each of the detected species is an enormous task. Nonetheless, these samples provide a benchmark to establish the potential clinical utility of sheath-flow SERS detection.

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“…1 a shows the setup used to perform the SERS experiments. Ag rough surface) 28,29 . 1 b displays the state-of-art gold coated plasmonic nanopores 6 which are shown to be capable of optically trapping 20 nm polystyrene beads 7 and localizing the SERS detection region in small volumes with high enhancement 8 .…”

Section: Sers and Particle Trapping In Plasmonic Nanoporesmentioning

confidence: 99%

“…The first thing that strikes our attention is that the strongest peak at 998 cm-1 in the bulk Raman spectrum of polystyrene, assigned to the aromatic ring breathing mode 31 , is absent in the SERS spectra taken on both the rough surface and inside the nanopore (see Fig. For 100-1000 nm particles 28,29 it is shown that the ring breathing mode can be observed. The only visible Raman peak in both SERS spectra is near 785 cm -1 , also appearing in the bulk Raman spectrum at 792 cm -1 , assigned to vibration of aromatic rings linked through gauche-gauche conformations of the aliphatic chain 31 .…”

Section: Figmentioning

confidence: 99%

Raman fingerprinting of single dielectric nanoparticles in plasmonic nanopores

Kerman

Chang

et al. 2015

Nanoscale

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Plasmonic nano-apertures are commonly used for the detection of small particles such as nanoparticles and proteins by exploiting electrical and optical techniques. Plasmonic nanopores are metallic nano-apertures sitting on a thin membrane with a tiny hole. It has been shown that plasmonic nanopores with a given geometry identify internal molecules using Surface Enhanced Raman Spectroscopy (SERS). However, label-free identification of a single dielectric nanoparticle requires a highly localized field comparable to the size of the particle. Additionally, the particle's Brownian motion can jeopardize the amount of photons collected from a single particle. Here, we demonstrate that the combination of optical trapping and SERS can be used for the detection and identification of 20 nm polystyrene nanoparticles in plasmonic nanopores. This work is anticipated to contribute to the detection of small bioparticles, optical trapping and nanotribology studies.

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Label-free in situ detection of individual macromolecular assemblies by surface enhanced Raman scattering

Cited by 21 publications

References 20 publications

Ultrasensitive Surface-Enhanced Raman Scattering Flow Detector Using Hydrodynamic Focusing

Ultrasensitive Surface-Enhanced Raman Scattering Flow Detector Using Hydrodynamic Focusing

Sheath flow SERS for chemical profiling in urine

Raman fingerprinting of single dielectric nanoparticles in plasmonic nanopores

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