Neil C. Shand

Detection of SERS active labelled DNA based on surface affinity to silver nanoparticles

Developments in specific DNA detection assays have been shown to be increasingly beneficial for molecular diagnostics and biological research. Many approaches use optical spectroscopy as an assay detection method and, owing to the sensitivity and molecular specificity offered, surface enhanced Raman scattering (SERS) spectroscopy has become a competitively exploited technique. This study utilises SERS to demonstrate differences in affinity of dye labelled DNA through differences in electrostatic interactions with silver nanoparticles. Results show clear differences in the SERS intensity obtained from single stranded DNA, double stranded DNA and a free dye label and demonstrate surface attraction is driven through electrostatic charges on the nucleotides and not the SERS dye. It has been further demonstrated that, through optimisation of experimental conditions and careful consideration of sequence composition, a DNA detection method with increased sample discrimination at lower DNA concentrations can be achieved.

Surface-Enhanced, Spatially Offset Raman Spectroscopy (SESORS) in Tissue Analogues

Surface-enhanced, spatially offset Raman spectroscopy (SESORS) combines the remarkable enhancements in sensitivity afforded by surface-enhanced Raman spectroscopy (SERS) with the non-invasive, subsurface sampling capabilities of spatially offset Raman spectroscopy. Taken together, these techniques show great promise for in vivo Raman measurements. Herein, we present a step forward for this technique, demonstrating SESORS through tissue analogues of six known and varied thicknesses, with a large number of distinct spatial offsets, in a backscattering optical geometry. This is accomplished by spin-coating SERS-active nanoparticles (NPs) on glass slides and monitoring the relative spectral contribution from the NPs and tissue sections, respectively, as a function of both the tissue thickness and the spatial offset of the collection probe. The results show that SESORS outperforms SERS alone for this purpose, the NP signal can be attained at tissue thicknesses of >6.75 mm, and greater tissue thicknesses require greater spatial offsets to maximize the NP signal, all with an optical geometry optimized for utility. This demonstration represents a step forward toward the implementation of SESORS for non-invasive, in vivo analysis.

Sensitive SERS nanotags for use with a hand-held 1064 nm Raman spectrometer

This is the first report of the use of a hand-held 1064 nm Raman spectrometer combined with red-shifted surface-enhanced Raman scattering (SERS) nanotags to provide an unprecedented performance in the short-wave infrared (SWIR) region. A library consisting of 17 chalcogenopyrylium nanotags produce extraordinary SERS responses with femtomolar detection limits being obtained using the portable instrument. This is well beyond previous SERS detection limits at this far red-shifted wavelength and opens up new options for SERS sensors in the SWIR region of the electromagnetic spectrum (between 950 and 1700 nm).

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.