Laser induced SERS switching using plasmonic heating of PNIPAM coated HGNs

This is the first report of SERS switching ‘on and off’ using laser induced plasmonic heating of poly(N-isopropylacrylamide) (PNIPAM) coated hollow gold nanoshells (HGNs). The degree of Raman enhancement for these thermosensitive SERS nanotags was controlled by plasmonic tuning of the properties of the HGNs

Rapid Raman mapping for chocolate analysis

Raman microspectroscopy mapping capabilities have advanced significantly and have been applied to cell and pharmaceutical tablet formulation analysis. Bulk Raman investigations of food and their constituents have been carried out but little work exists on the application of Raman mapping capabilities to food. Here, we assess the applicability of Raman microspectroscopy mapping to the analysis of chocolate and examine both white and milk chocolate samples. It was found that the sucrose, lactose and fat constituents of white chocolate could be extracted and spatially resolved, indicating that the sucrose and lactose formed particles within a matrix of 'fats'. Fluorescence from cocoa solids present in milk chocolate prevented chemical mapping with the instrumentation used. Raman mapping should provide a powerful analytical technique for the analysis and development of food products

Qualitative SERS analysis of G-quadruplex DNAs using selective stabilising ligands

Nucleic acids are of key biological importance due to their range of functions and ability to form various different structures, with an example of emerging significance being quadruplexes formed by guanine-rich sequences. These guanine rich sequences are found in different regions of the genome such as telomeres, gene promoters and introns and UTRs of mRNAs. Here a new approach has been developed that utilises surface enhanced Raman scattering (SERS) for the detection of the formation of G-quadruplexes. Three G-quadruplex stabilising ligands that each have their own unique SERS response were used in this study and their ability to act as reporters assessed. A SERS response was only obtained from the ligands in the absence of G-quadruplex formation. This resulted in an "on/off" method which was successfully used to qualitatively detect the formation of G-quadruplex using quadruplex-forming sequences such as human telomeric and C-MYC promoter DNAs. The unique SERS spectra of each stabilising ligand offer the potential for use of SERS to study higher order DNA structures. This work shows that the ligands used can act simultaneously as a potential therapeutic stabilising agent and a SERS reporter, therefore allowing the use of SERS as a method of analysis of the formation of G-quadruplex DNAs

Silver colloids as plasmonic substrates for direct label-free surface-enhanced Raman scattering analysis of DNA

Ultrasensitive direct SERS analysis offers a powerful analytical tool for the structural characterization and classification of nucleic acids. However, acquisition of reliable spectral fingerprints of such complex biomolecules poses important challenges. In recent years, many efforts have been devoted to overcome these limitations, mainly implementing silver colloids as plasmonic substrates. However, a reliable cross-comparison of results reported in the recent literature is extremely hard to achieve, mostly due to the broad set of different surface properties of the plasmonic nanoparticles. Herein, we perform a thorough investigation of the role played by the metal/liquid interface composition of silver colloids in the direct label-free SERS analysis of DNA. Target molecules of increasing complexity, from short homopolymeric strands to long genomic duplexes, were used as probes. We demonstrate how apparently subtle changes in the colloidal surface chemistry can dramatically modify the affinity and the final SERS spectral profile of DNA. This has significant implications for the future design of new analytical strategies for the detection of DNA using SERS without labels

Introducing 12 new dyes for use with oligonucleotide functionalised silver nanoparticles for DNA detection with SERS

Oligonucleotide functionalised metallic nanoparticles (MNPs) have been shown to be an effective tool in the detection of disease-specific DNA and have been employed in a number of diagnostic assays. The MNPs are also capable of facilitating surface enhanced Raman scattering (SERS) enabling detection to become highly sensitive. Herein we demonstrate the expansion of the range of specific SERS-active oligonucleotide MNPs through the use of 12 new Raman-active monomethine and trimethine chalcogenopyrylium and benzochalcogenopyrylium derivatives. This has resulted in an increased ability to carry out multiplexed analysis beyond the current small pool of resonant and non-resonant Raman active molecules, that have been used with oligonucleotide functionalised nanoparticles. Each dye examined here contains a variation of sulphur and selenium atoms in the heterocyclic core, together with phenyl, 2-thienyl, or 2-selenophenyl substituents on the 2,2’,6, and 6’ positions of the chalcogenopyrylium dyes and 2 and 2’ positions of the benzochalcogenopyrylium dyes. The intensity of SERS obtained from each dye upon conjugate hybridisation with a complementary single stranded piece of DNA was explored. Differing concentrations of each dye (1000, 3000, 5000 and 7000 equivalents per NP-DNA conjugate) were used to understand the effects of Raman reporter coating on the overall Raman intensity. It was discovered that dye concentration did not affect the target/control ratio, which remained relatively constant throughout and that a lower concentration of Raman reporter was favourable in order to avoid NP instability. A relationship between the dye structure and SERS intensity was discovered, leaving scope for future development of specific dyes containing substituents favourable for discrimination in a multiplex by SERS. Methine dyes containing S and Se in the backbone and at least 2 phenyls as substituents give the highest SERS signal following DNA-induced aggregation. Principal component analysis (PCA) was performed on the data to show differentiation between the dye classes and highlight possible future multiplexing capabilities of the 12 investigated dyes

Elucidation of the bonding of a near infrared dye to hollow gold nanospheres : a chalcogen tripod

Infrared surface enhanced Raman scattering (SERS) is an attractive technique for the in situ detection of nanoprobes in biological samples due to the greater depth of penetration and reduced interference compared to SERS in the visible region. A key challenge is to understand the surface layer formed in suspension when a specific label is added to the SERS substrate in aqueous suspension. SERS taken at different wavelengths, theoretical calculations, and surface-selective sum frequency generation vibrational spectroscopy (SFG-VS) were used to define the surface orientation and manner of attachment of a new class of infrared SERS label with a thiopyrylium core and four pendant 2-selenophenyl rings. Hollow gold nanospheres (HGNs) were used as the enhancing substrate and two distinct types of SERS spectra were obtained. With excitation close to resonance with both the near infrared electronic transition in the label (max 826 nm) and the plasmon resonance maximum (690 nm), surface enhanced resonance Raman scattering (SERRS) was obtained. SERRS indicates that the major axis of the core is near to perpendicular to the surface plane and SFG-VS obtained from a dried gold film gave a similar orientation with the major axis at an angle 64°-85° from the surface plane. Longer excitation wavelengths give SERS with little or no molecular resonance contribution and new vibrations appeared with significant displacements between the thiopyrylium core and the pendant selenophene rings. Analysis using calculated spectra with one or two rings rotated indicates that two rings on one end are rotated towards the metal surface to give an arrangement of two selenium and one sulphur atoms directly facing the gold structure. The spectra, together with a space filled model, indicate that the molecule is strongly adsorbed to the surface through the selenium and sulphur atoms in an arrangement which will facilitate layer formation

Quantification of functionalised gold nanoparticle-targeted knockdown of gene expression in HeLa cells

Introduction: Gene therapy continues to grow as an important area of research, primarily because of its potential in the treatment of disease. One significant area where there is a need for better understanding is in improving the efficiency of oligonucleotide delivery to the cell and indeed, following delivery, the characterization of the effects on the cell. Methods: In this report, we compare different transfection reagents as delivery vehicles for gold nanoparticles functionalized with DNA oligonucleotides, and quantify their relative transfection efficiencies. The inhibitory properties of small interfering RNA (siRNA), single-stranded RNA (ssRNA) and single-stranded DNA (ssDNA) sequences targeted to human metallothionein hMT-IIa are also quantified in HeLa cells. Techniques used in this study include fluorescence and confocal microscopy, qPCR and Western analysis. Findings: We show that the use of transfection reagents does significantly increase nanoparticle transfection efficiencies. Furthermore, siRNA, ssRNA and ssDNA sequences all have comparable inhibitory properties to ssDNA sequences immobilized onto gold nanoparticles. We also show that functionalized gold nanoparticles can co-localize with autophagosomes and illustrate other factors that can affect data collection and interpretation when performing studies with functionalized nanoparticles. Conclusions: The desired outcome for biological knockdown studies is the efficient reduction of a specific target; which we demonstrate by using ssDNA inhibitory sequences targeted to human metallothionein IIa gene transcripts that result in the knockdown of both the mRNA transcript and the target protein

Enjolras; The Song of the Patriot

80.7568.307 – “Enjolras; The Song of the Patriot”: Edmundus Scotus, R. Q. S.: D. P. Faulds: 1865: Vocal Solo

Drummer Boys of Shiloh

80.7568.292 – “Drummer Boys of Shiloh”: Will S. Hays: D. P. Faulds: 1863: Voice Solo

Galop Di Bravura

80.7568.382 – “Galop Di Bravura”: Schulhoff, Jules: D. P. Faulds & Co.: Louisville: Dance Music: Galop: n.d.: Solo Piano