Surface-enhanced Raman spectroscopy for analysis of PCR products of viral RNA of hepatitis C patients (original) (raw)
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Analytical and Bioanalytical Chemistry, 2016
Gunshot residues (GSR) result from the discharge of a firearm being a potential piece of evidence in criminal investigations. The macroscopic GSR particles are basically formed by burned and non-burned gunpowder. Motivated by the demand of trace analysis of these samples, in this paper, the use of surface-enhanced Raman scattering (SERS) was evaluated for the analysis of gunpowders and macroscopic GSR particles. Twenty-one different smokeless gunpowders were extracted with ethanol. SERS spectra were obtained from the diluted extracts using gold nanoaggregates and an excitation wavelength of 633 nm. They show mainly bands that could be assigned to the stabilizers diphenylamine and ethylcentralite present in the gunpowders. Then, macroscopic GSR particles obtained after firing two different ammunition cartridges on clothing were also measured using the same procedure. SERS allowed the detection of the particles collected with an aluminum stub from cloth targets without interferences from the adhesive carbon. The results demonstrate the great potential of SERS for the analysis of macroscopic GSR particles. Furthermore, they indicate that the grain-tograin inhomogeneity of the gunpowders needs to be considered.
Photodiagnosis and Photodynamic Therapy
Traditional pesticide residue detection methods are usually complicated, time consuming, and expensive. Rapid, portable, online, and real-time detection kits are the developing direction of pesticide testing. In this paper, we used a surface-enhanced Raman spectroscopy (SERS) technique to detect the organophosphate pesticide residue of phorate and fenthion in apple skin, for the purpose of finding a fast, simple, and convenient detection method for pesticide detection. The results showed that the characteristic wavenumbers of the two organophosphorus pesticides are more easily identified using SERS. We selected the Raman peaks at 728 cm À1 of phorate and 1215 cm À1 of fenthion as the target peaks for quantitative analysis, and utilized internal standards to establish linear regression models for phorate and fenthion. The detection limit was 0.05 mg/L for phorate and 0.4 mg/L for fenthion. This method can be used as a quantitative analytical reference for the detection of phorate and fenthion.
Fast Analysis of Complete Macroscopic Gunshot Residues on Substrates Using Raman Imaging
Applied spectroscopy, 2015
Raman spectroscopy has emerged as a viable technique for the organic analysis of gunshot residues (GSRs), offering additional information to the well-established analysis using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX). In this article, a Raman imaging system with an electron-multiplying coupled-charged device (EMCCD) camera was used to analyze complete GSR particles from both conventional and nontoxic ammunition fired at different cloth targets. The same cloths were then stained with blood to mimic real evidence and measured. The direct analysis using Raman imaging of the GSR particles collected with the stubs used for SEM-EDX analysis (the frequent method used for GSR collection) was evaluated. Multivariate curve-resolution and chemical-mapping methods were applied to the spectroscopic data to identify and highlight the signal corresponding to the GSR particles and differentiate them from the substrates. It was confirmed that both mea...
Analytical Chemistry, 2012
The ability to unequivocally identify a gunshot residue (GSR) when a firearm is discharged is a very important and crucial part of crime scene investigation. To date, the great majority of the analyses have focused on the inorganic components of GSR, but the introduction of "lead-free" or "nontoxic" ammunitions makes it difficult to prevent false negatives. This study introduces a fast methodology for the organic analysis of GSR using Raman spectroscopy. Six different types of ammunition were fired at short distances into cloth targets, and the Raman spectra produced by the GSR were measured and compared with the spectra from the unfired gunpowder ammunition. The GSR spectrum shows high similarity to the spectrum of the unfired ammunition, allowing the GSR to be traced to the ammunition used. Additionally, other substances that might be found on the victim's, shooter's, or suspect's clothes and might be confused with GSR, such as sand, dried blood, or black ink from a common ballpoint pen, were analyzed to test the screening capability of the Raman technique. The results obtained evidenced that Raman spectroscopy is a useful screening tool when fast analysis is desired and that little sample preparation is required for the analysis of GSR evidence.
Evaluation of Surface-Enhanced Resonance Raman Scattering for Quantitative DNA Analysis
Analytical Chemistry, 2004
The labeling of biological species using dyes has become common practice to aid in their detection, and immediate positive identification of specific dyes in high dilution is a key requirement. Here the detection by surfaceenhanced resonance Raman scattering (SERRS) of eight commercially available dye labels (ROX, rhodamine 6G, HEX, FAM, TET, Cy3, Cy5, TAMRA) attached to oligonucleotide strands is reported. Each of the eight labels was easily detected by using the SERRS from silver nanoparticles to produce a unique, molecularly specific spectrum. The conditions were optimized to obtain the best signal enhancement, and linear concentration graphs at low oligonucleotide concentrations were obtained. At higher concentrations (above ∼10 -8 mol dm -3 ), curvature was introduced into the concentration graphs with the exception of rhodamine 6G, TET, and FAM, which gave linearity over the entire concentration range studied. Detection limits as low as 0.5 fmol were obtained, with lower possible if a smaller sample was analyzed. Investigation was also carried out into the effect of a Tris-HCl buffer containing the surfactant Tween 20 to aid in the prevention of surface adhesion of the oligonucleotides to the sample vessels at ultralow concentrations. The Tween 20 allowed lower detection limits to be obtained for each of the labels studied. This study shows that the different dyes commonly used with oligonucleotides can give quantitative SERRS at concentration levels not possible when the same dyes are used with fluorescence detection.
Reviews in Analytical Chemistry, 2013
The inelastic scattering of light, Raman scattering, presents a very low cross section. However, the signal can be amplified by several orders of magnitude, leading to the so-called surface-enhanced Raman scattering (SERS) phenomenon. Basically, the SERS effect is achieved when the target molecule (analyte) is adsorbed onto metallic nanoparticles, usually noble metals. This article presents an overview of the applications of SERS to cancer diagnosis and the detection of pesticides, explosives, and drugs (illicit and pharmacological). SERS is routinely applied nowadays to detect and identify analytes at very low concentrations, including for single-molecule detection. However, the application of SERS as an analytical tool requires reliable and reproducible SERS substrates, in terms of enhancement factors, which depends on the size, shape, and aggregation of the metallic nanoparticles. Therefore, the production of reliable and reproducible SERS substrates is a challenge in the field. Besides, the metallic nanoparticles can also induce changes in the system by possible interactions with the analyte under investigation, which must be taken into account. This review will present work in which, under certain specific experimental conditions, SERS has been analytically applied.
Raman microspectroscopic mapping as a tool for detection of gunshot residue on adhesive tape
Analytical and Bioanalytical Chemistry, 2018
Our research group previously reported a novel method for the detection of gunshot residue (GSR) via tape lifting combined with Raman microspectroscopic mapping and multivariate analysis. This initial study achieved proof of concept for this approach. Here, we report validation studies which investigate the reproducibility/ruggedness and specificity of the approach. Raman mapping for GSR detection on adhesive tape was performed on an independent Raman microscope, not used to generate the training set. These independent spectra were classified against the original training dataset using support vector machine discriminant analysis (SVM-DA). The resulting classification rates of 100% illustrate the reproducibility of the technique, its independence upon a specific instrument and provide an external validation for the approach. Additionally, the same procedure for GSR collection (tape lifting) was performed to collect samples from environmental sources, which could potentially provide false-positive assignments for current GSR analysis techniques. Thus, particles associated with automotive mechanics were collected. Automotive brake and tire materials are often composed of the heavy metals lead, barium, and antimony, which are the key elements targeted by current GSR detection technique. It was determined that Raman spectroscopic analysis was not susceptible to misclassifications from these samples. Results from these validation experiments illustrate the great potential of Raman microspectroscopic mapping used with tape lifting as a viable complimentary tool to current methodologies for GSR detection. Furthermore, current methodologies are not well-developed for automated organic GSR detection. Illustrated here, Raman microscoptrosocpic mapping has the potential for the automatic identification of organic GSR.
Detection of explosives based on surface-enhanced Raman spectroscopy
Applied Optics, 2010
In this study we present a device based on surface-enhanced Raman scattering (SERS) for the detection of airborne explosives. The explosives are resublimated on a cooled nanostructured gold substrate. The explosives trinitrotoluene (TNT) and triacetone triperoxide (TATP) are used. The SERS spectrum of the explosives is analyzed. Thus, TNT is deposited from an acetonitrile solution on the gold substrate. In the case of TATP, first the bulk TATP Raman spectrum was recorded and compared with the SERS spectrum, generated by deposition out of the gas phase. The frequencies of the SERS spectrum are hardly shifted compared to the spectrum of bulk TATP. The influence of the nanostructured gold substrate temperature on the signals of TATP was studied. A decrease in temperature up to 200 K increased the intensities of the TATP bands in the SERS spectrum; below 200 K, the TATP fingerprint disappeared.