Turning up the lights - fabrication of brighter SERRS nanotags

Brighter SERRS nanotags ideal for improved SERRS imaging were prepared by the controlled addition of electrolyte producing a dimer enriched solution, which was incubated with a Raman reporter before being stabilised by a polyethylene glycol (PEG) shell

Mixed metal nanoparticle assembly and the effect on surface enhanced raman scattering

Here we report the assembly of mixed metal nanoparticles using an oligonucleotide-templated approach. Substitution of one of the gold nanoparticle probes with an analagous silver probe to produce a hetero-metal duplex permitted surface enhanced Raman scattering of the dye label, exploiting the improved surface enhancement properties of silver nanoparticles whilst maintaining the surface chemistry benefits of gold nanoaprticle

Investigation of silver nanoparticle assembly following hybridization with different lengths of DNA

Assays involving the controlled assembly of oligonucleotide-functionalised nanoparticles have been widely investigated for the detection of short, specific sequences of DNA. The surface plasmon resonance changes that result from the near-field coupling of the nanoparticles provide a means for investigating formation of these assemblies. For these assays to be effective in practice, there needs to be rapid and efficient hybridisation of the functionalised nanoparticles with target DNA. However, it is known that the hybridisation rate is adversely affected by increased numbers of non-hybridising bases on the target DNA strand. This study investigates the DNA-directed assembly of oligonucleotide-functionalised silver nanoparticles, with the aim of identifying the parameters that will maximise hybridisation efficiency with long target sequences. The study shows that increasing the length of probes from 12 to 24 bases, and orientating them in a tail-to-tail rather than a head-to-tail configuration, results in significantly enhanced hybridisation with a long target sequence. The use of a volume excluding polymer such as dextran sulphate in the buffer also markedly improves hybridisation. This information will prove useful for researchers involved in the design of DNA-mediated nanoparticle assembly assays, particularly for the detection of long sequences of DNA

Multiplex in vitro detection using SERS

The ability to detect multiple disease-related targets from a single biological sample in a quick and reliable manner is of high importance in diagnosing and monitoring disease. The technique known as surface enhanced Raman scattering (SERS) has been developed for the simultaneous detection of multiple targets present in biological samples. Advances in the SERS method have allowed for the sensitive and specific detection of biologically relevant targets, such as DNA and proteins, which could be useful for the detection and control of disease. This review focuses on the strengths of SERS for the detection of target molecules from complex mixtures and the clinical relevance of recent work combining SERS with multiplexed detection of biological targets

Bayesian modelling and quantification of Raman spectroscopy

Raman spectroscopy can be used to identify molecules such as DNA by the characteristic scattering of light from a laser. It is sensitive at very low concentrations and can accurately quantify the amount of a given molecule in a sample. The presence of a large, nonuniform background presents a major challenge to analysis of these spectra. To overcome this challenge, we introduce a sequential Monte Carlo (SMC) algorithm to separate each observed spectrum into a series of peaks plus a smoothly-varying baseline, corrupted by additive white noise. The peaks are modelled as Lorentzian, Gaussian, or pseudo-Voigt functions, while the baseline is estimated using a penalised cubic spline. This latent continuous representation accounts for differences in resolution between measurements. The posterior distribution can be incrementally updated as more data becomes available, resulting in a scalable algorithm that is robust to local maxima. By incorporating this representation in a Bayesian hierarchical regression model, we can quantify the relationship between molecular concentration and peak intensity, thereby providing an improved estimate of the limit of detection, which is of major importance to analytical chemistry

Working memory matters: a series of case studies evaluating the effect of a working memory intervention in children with early onset otitis media

Otitis Media (glue ear) delays reading (Kindig & Richards, 2000) by impacting on phonological processing, and may affect working memory development (Mody et al, 1999). Reported links between working memory capacity and school success (Bourke & Adams, 2003; Gathercole, Pickering, Knight & Stegman, 2004), suggest that working memory has a crucial role in learning. Deficits have been linked to anxiety during task performance (Hadwin, Brogan & Stevenson, 2005) and low self-esteem (Alloway, Gathercole, Kirkwood & Elliott, 2009).\ud \ud Sixteen children aged seven to ten with a history of early onset Otitis Media, together with a comparison group of twelve children were assessed on a range of measures of phonological processing, single word and non-word reading, non-verbal reasoning and working memory, and an attitude to self and school rating scale, before and after working memory training. Semi-structured interviews and classroom observations of learning behaviours were used to elaborate the findings from the quantitative data.\ud \ud Significant differences were found between the groups before training in verbal and visuo-spatial short term and working memory, and non-word reading. Following training these differences were no longer significant. Performance in reading and phonological tasks was found to improve for both groups following training. Mean scores for responses to the learning attitudes rating scales were not significantly different before or after training, but large individual differences were found for children in both groups. Case studies are presented of individual children in the Otitis Media group.\ud \ud The results indicate that, as found in previous studies, a history of Otitis Media can result in weaknesses in phonological processes, memory and literacy development, and the original contribution of this study indicates that these may be ameliorated by a working memory intervention. Improvements in working memory did not appear to affect children’s overall learning identities but more positive feelings were found after training for several children

Mixed-monolayer glyconanoparticles for the detection of cholera toxin by surface enhanced raman spectroscopy

The same interactions that a pathogen uses for establishment in a host can be exploited in its detection. The carbohydrates comprising the intestinal cell surface GM1-ganglioside, are targeted by vibrio cholerae via the lectin, cholera toxin, to initiate infection. We report on the preparation of mixed-monolayer, carbohydrate-coated silver nanoparticles (glyconanoparticles) for the sensitive (56 ng/mL), low volume detection of cholera toxin B-subunit (CTB) in synthetic freshwater samples and in 5 minutes by surface enhanced Raman spectroscopy (SERS). The detection limit falls within the recommended detection range and matches WHO approved test limits. PEGylated galactose and sialic acid are added in a specific ratio to coat the particles in GM1-ganglioside mimics for interaction with CTB and display a synergic effect greater than either glycan alone. This demonstrates the first use of a mixed-monolayer glyconanoparticle which mimics the GM1 ligand, allowing selective interaction with CTB

Bacterial meningitis pathogens identified in clinical samples using a SERS DNA detection assay

This communication reports the first demonstration of the detection of Streptococcus pneumoniae and Neisseria meningitidis bacterial DNA extracted from anonymous patient CSF samples and assesses the applicability of a previously developed SERS based DNA detection assay as a platform for the detection of multiple meningitis pathogens from clinical samples

Investigation of Cellular Uptake Mechanism of Functionalised Gold Nanoparticles into Breast Cancer Using SERS

Gold nanoparticles (AuNPs) are widely used in various applications such as cancer imaging and drug delivery. The functionalisation of AuNPs has been shown to affect their cellular internalisation, accumulation and targeting efficiency. The mechanism of cellular uptake of functionalised AuNPs by different cancer cells is not well understood. Therefore, a detailed understanding of the molecular processes is necessary to improve AuNPs for their selective uptake and fate in specific cellular systems. This knowledge can greatly help in designing nanotags with higher cellular uptake for more selective and specific targeting capabilities with less off-target effects. Here, we demonstrate for the first time a straightforward and non-destructive 3D surface enhanced Raman spectroscopy (SERS) imaging approach to track the cellular uptake and localisation of AuNPs functionalised with an anti-ERα (estrogen receptor alpha) antibody in MCF-7 ERα-positive human breast cancer cells under different conditions including temperature and dynamin inhibition. 3D SERS enabled information rich monitoring of the intracellular internalisation of the SERS nanotags. It was found that ERα-AuNPs were internalised by MCF-7 cells in a temperature-dependent manner suggesting an active endocytosis-dependent mechanism. 3D SERS cell mapping also indicated that the nanotags entered MCF-7 cells using dynamin dependent endocytosis, since dynamin inhibition resulted in the SERS signal being obtained from, or close to, the cell surface rather than inside the cells. Finally, ERα-AuNPs were found to enter MCF-7 cells using an ERα receptor-mediated endocytosis process. This study addresses the role of functionalisation of SERS nanotags in biological environments and highlights the benefits of using 3D SERS for the investigation of cellular uptake processes