Graeme McNay

Surface-enhanced raman scattering (SERS) and surface-enhanced resonance raman scattering (SERRS): a review of applications

Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS) can provide positive identification of an analyte or an analyte mixture with high sensitivity and selectivity. Better understanding of the theory and advances in the understanding of the practice have led to the development of practical applications in which the unique advantages of SERS/SERRS have been used to provide effective solutions to difficult analytical problems. This review presents a basic theory and illustrates the way in which SERS/SERRS has been developed for practical use.

Multiple labelled nanoparticles for bio detection.

Remote nanoparticle detection is required for the development of in situ biological probes. Here we describe the labelling of silver nanoparticles to produce multiply coded particles which can be detected by surface enhanced resonance Raman scattering (SERRS). There is a potential for thousands of codes to be written and read without the need for spatial resolution of components of the code. The use of these systems in bioanlaysis and in situ detection is discussed.

Evaluation of a Commercially Developed Semiautomated PCR–Surface-Enhanced Raman Scattering Assay for Diagnosis of Invasive Fungal Disease

ABSTRACT Nonculture-based tests are gaining popularity in the diagnosis of invasive fungal disease (IFD), but PCR is excluded from disease-defining criteria because of limited standardization and a lack of commercial assays. Commercial PCR assays may have a standardized methodology while providing quality assurance. The detection of PCR products by a surface-enhanced Raman scattering (SERS) assay potentially provides superior analytical sensitivity and multiplexing capacity compared to that of real-time PCR. Using this approach, the RenDx Fungiplex assay was developed to detect Candida and Aspergillus. Analytical and clinical evaluations of the assay were undertaken using extraction methods according to European Aspergillus PCR Initiative (EAPCRI) recommendations. A total of 195 previously extracted samples (133 plasma, 49 serum, and 13 whole blood) from 112 patients (29 with proven/probable IFD) were tested. The 95% limit of detection of Candida and Aspergillus was 200 copies per reaction, with an overall reproducibility of 92.1% for detecting 20 input copies per PCR, and 89.8% for the nucleic acid extraction–PCR-SERS process for detecting fungal burdens of <20 genome equivalents per sample. A clinical evaluation showed that assay positivity significantly correlated with IFD (P < 0.0001). The sensitivity of the assay was 82.8% and was similar for both Candida (80.0%) and Aspergillus (85.7%). The specificity was 87.5% and was increased (97.5%) by using a multiple (≥2 samples) PCR-positive threshold. In summary, the RenDx Fungiplex assay is a PCR-SERS assay for diagnosing IFD and demonstrates promising clinical performance on a variety of samples. This was a retrospective clinical evaluation, and performance is likely to be enhanced through a prospective analysis of clinical validity and by determining clinical utility.

Surface-enhanced resonance Raman scattering in optical tweezers using co-axial second harmonic generation

Silica particles were partially coated with silver, and a suitable chromophore, such that they could be simultaneously trapped within an optical tweezers system, and emit a surface-enhanced resonance Raman scattering (SERRS) response. A standard 1064 nm TEM00 mode laser was used to trap the bead whilst a frequency doubling crystal inserted into the beam gave several microwatts of 532 nm co-linear light to excite the SERRS emission. The con fi guration has clear applications in providing apparatus that can simultaneously manipulate a particle whilst obtaining surface sensitive sensory information.

Three-dimensional optical trapping of partially silvered silica microparticles

We demonstrate three-dimensional trapping of micrometer-diameter silica particles, partially coated with silver, within conventional optical tweezers. Although metallic particles are usually repelled from the beam focus by the scattering force, we show that transparent spheres partially coated with silver can be trapped with efficiencies comparable with dielectric particles. The trapping characteristics of these particles are examined as a function of metallic coverage, and the application of these particles to surface-enhanced resonance Raman scattering is investigated.

Distance detection using Raman scattering: a new tagging technology

Surface enhanced resonance Raman scattering (SERRS) provides an increase in sensitivity over Raman scattering of about 1014 and rivals fluorescence in terms of its quantum efficiency. With the use of modern edge and notch filters and CCD cameras, the price and complexity of Raman spectroscopy equipment has decreased rapidly. This means that the potential advantages of SERRS are now much easier to release for use for practical purposes. The technique has specific advantages in terms of sensitivity and coding for use for tagging.