Portable Raman System Research Articles

In vitro discrimination and classification of Microbial Flora of Poultry using two dispersive Raman spectrometers (microscope and Portable Fiber-Optic systems) in tandem with chemometric analysis

Discrimination and classification of eight strains related to meat spoilage and pathogenic microorganisms commonly found in poultry meat were successfully carried out using two dispersive Raman spectrometers (Microscope and Portable Fiber-Optic systems) in combination with chemometric methods. Principal components analysis (PCA) and multi-class support vector machines (MC-SVM) were applied to develop discrimination and classification models. These models were certified using validation data sets which were successfully assigned to the correct bacterial species and even to the right strain. The discrimination of bacteria down to the strain level was performed for the pre-processed spectral data using a 3-stage model based on PCA. The spectral features and differences among the species on which the discrimination was based were clarified through PCA loadings. In MC-SVM the pre-processed spectral data was subjected to PCA and utilized to build a classification model. When using the first two components, the accuracy of the MC-SVM model was 97.64% and 93.23% for the validation data collected by the Raman Microscope and the Portable Fiber-Optic Raman system, respectively. The accuracy reached 100% for the validation data by using the first eight and ten PC's from the data collected by Raman Microscope and by Portable Fiber-Optic Raman system, respectively. The results reflect the strong discriminative power and the high performance of the developed models, the suitability of the pre-processing method used in this study and that the low accuracy of the Portable Fiber-Optic Raman system does not adversely affect the discriminative power of the developed models.

Using Raman Spectroscopy for Assessing Cervical Change During Labor: An Objective Approach to Labor Management [31T

INTRODUCTION: Subjective assessment of digital examination can lead to different interpretations of cervical change and may affect labor management decisions. The aim of this study is to assess using Raman Spectroscopy to identify biochemical signatures associated with cervical change during labor. METHODS: At a major medical center, 10 adult pregnant patients were recruited and enrolled. The exclusion criteria were non-English speakers, prior preterm birth, prior LEEP, preterm labor or PROM. A portable Raman system with imaging-spectrograph, 785 nm diode laser, and fiber-optic probe were used. Measurements were taken at each prenatal visit starting at 37 weeks and during labor. The probe was placed at 3-6-9, and 12 o'clock positions and spectra were obtained. Both prenatal and labor peak ratios were compared and analyzed as function of cervical dilation. RESULTS: The average age and BMI were 25 years and 35.4 kg/m2 respectively. 40% underwent induction of labor with an average cervical dilation of 2.7 cm on admission. Raman peak amplitudes associated with extracellular matrix (ECM) proteins displayed significant differences between spectra measured at prenatal visits vs. labor. These included amide III band at 1253 cm-1 (P=.004), collagen and lipid-associated band at 1454 cm-1 (p=.001), and amide I band 1654 cm-1 (P=1.05x10-5). The 1454 cm-1band showed a distinct increase as a function of cervical dilation. CONCLUSION: Our study demonstrates that Raman spectroscopy is sensitive to biochemical changes in the cervix prior to the onset of labor as well as during labor progress. This may suggest reorganization of the ECM as the cervix remodels during labor.

An improved method based on a new wavelet transform for overlapped peak detection on spectrum obtained by portable Raman system

Peak detection is a particularly important pre-processing step in chemical identification using Raman spectra. At present, most peak detection methods have limited applicability when there are overlapping peaks, especially the spectrum measured by portable spectrometers with low resolution. In this paper, an improved method is proposed based on the application of continuous wavelet transform (CWT) peak detection using a new wavelet to the deconvolved Raman spectrum. The new wavelet has a smaller linewidth and is more similar to the intrinsic Lorentz line profile of the Raman spectrum. It, therefore, has several advantages with regard to the detection of overlapping peaks. The proposed method was evaluated using the Raman spectrum of solid amino acid mixtures, and the results show that it is better at detecting overlapping peaks than the two other investigated wavelets. The receiver operating characteristic curves show that this method can detect more true peaks while maintaining a low false discovery rate. Moreover, the maximum of the true positive rate is the largest in the new approach, which indicates better performance for overlapping peak detection.

Selective Monitoring of Oxyanion Mixtures by a Flow System with Raman Detection.

Raman spectroscopy is a selective detection system scarcely applied for the flow analysis of solutions with the aim of detecting several compounds at once without a previous separation step. This work explores the potential of a portable Raman system in a flow system for the selective detection of a mixture of seven oxyanions (carbonate, sulphate, nitrate, phosphate, chlorate, perchlorate, and thiosulphate). The specific bands of these compounds (symmetric stretching Raman active vibrations of carbonate at 1068 cm−1, nitrate at 1049 cm−1, thiosulphate at 998 cm−1, phosphate at 989 cm−1, sulphate at 982 cm−1, perchlorate at 935 cm−1, and chlorate at 932 cm−1) enabled their simultaneous detection in mixtures. Although the oxyanions’ limit of detection (LOD) was rather poor (in the millimolar range), this extremely simple system is very useful for the single-measurement detection of most of the oxyanions in mixtures, without requiring a previous separation step. In addition, quantitative determination of the desired oxyanion can be performed by means of the corresponding calibration line. These are important advantages for controlling in-line processes in industries like those manufacturing fertilizers, pharmaceuticals, chemicals, or food, among others.

Lipophilic marine biotoxins SERS sensing in solutions and in mussel tissue

To detect and recognise three structurally related marine biotoxins responsible for the diarrheic shellfish poisoning (DSP) symptom, namely okadaic acid (OA), dinophysistoxin-1 (DTX-1) and dinophysistoxin-2 (DTX-2) respectively, as well as the structurally different yessotoxin (YTX), we developed a novel surface-enhanced micro-Raman scattering (micro-SERS) approach to investigate for the first time their micro-SERS signalling in solution and jointly analysed them in conjunction with the normal and toxic mussel tissue. YTX provided the main SERS feature surprisingly similar to DTX-1 and DTX-2, suggesting similar molecular adsorption mechanism with respect to the AgNPs. A fingerprint SERS band at 1017 cm−1 characteristic for the C-CH3 stretching in DTX-1 and DTX-2 and absent in OA SERS signal, allowed direct SERS discrimination of DTX-1,2 from OA. In acid form or as dissolved potassium salt, OA showed reproducible SERS feature for 0.81 μM to 84.6 nM concentrations respectively, while its ammonium salt slightly changed the overall SERS signature. The inherently strong fluorescence of the shellfish tissue, which hampers Raman spectroscopy analysis, further increases when toxins are present in tissue. Through SERS, tissue fluorescence is partially quenched. Artificially intoxicated mussel tissue with DSP toxins and incubated with AgNPs allowed direct SERS evidence of the toxin presence, opening a novel avenue for the in situ shellfish tracking and warning via micro-SERS. Natural toxic tissue containing 57.91 μg kg−1 YTX (LC-MS confirmed) was micro-SERS assessed to validate the new algorithm for toxins detection. We showed that a portable Raman system was able to reproduce the lab-based SERS results, being suitable for in situ raw seafood screening. The new approach provides an attractive, faster, effective and low-cost alternative for seafood screening, with economic, touristic and sustainable impact in aquaculture, fisheries, seafood industry and consumer trust.

Quantification of trace chemicals in unknown complex systems by SERS

The chemical quantitative analysis at trace level has been widely explored by means of various techniques. While it still remains challenging to achieve ultrasensitive but facile, rapid, and inexpensive detection methods. In this paper, the possibility of employing surface-enhanced Raman scattering technique on a portable Raman system for rapid and accurate quantitative analysis of target chemicals in unknown systems was investigated. This detection approach contains 3 steps: (1) adding target chemicals with different amount to the initial unknown solution, leading to new solutions with target molecules of various concentrations; (2) Obtaining different samples’ SERS spectra and capturing featured SERS peaks whose intensity grew up with the addition of target chemicals; (3) examining the relationship between featured peak intensity increment after adding target chemicals and its corresponding addition amount, and thus we could perform quantitative analysis of the chemical in an unknown solution and obtain its initial concentration. The validity of this method was systematically demonstrated by estimating the concentrations of 2-Naphthalenethiol (2-NaT) and 4-Mercaptopyridine (4-MPY) both in their single-component solutions and binary solutions, respectively. Predictions are close to their real values. Furthermore, we successfully predicted the concentrations of malachite green (MG) in fish water and benzidine in ground water. This study clearly demonstrates an accurate and facile approach to calculate the concentration of target chemicals in unknown systems, which fully exploit the potential of SERS quantitative analysis.

(Invited) Dielectrophoretic Capture and Detection of Microbial Pathogens Using Nanoelectrode Arrays

Rapid and highly sensitive detection of pathogenic microbes is critical for food safety and environmental protection. To achieve this, it requires combining novel sample preparation techniques and extremely sensitive detection methods. In this presentation, I summarize a series of studies in my lab on developing a nanoscale dielectrophoresis (DEP) device for effective capturing and concentrating pathogenic particles such as viral and bacterial particles in a fluidic chip. This technique was then integrated with various detection methods such as fluorescence imaging, surface enhanced Raman spectroscopy (SERS) and real-time impedance measurements for quantitative assessment of the pathogen concentration. Due to the small size (~1 micron for bacterial cells and ~100 nm for viral particles), it is challenging to capture and concentrating these pathogenic particles from dilute solutions. Here we demonstrate that the highly focused electric field at the tip of an embedded nanoelectrode array can be utilized to generate a large DEP force to effectively manipulate pathogenic particles. The nanoelectrode array was made of vertically aligned carbon nanofibers (VACNFs), about 5 micron in length and 100 nm in diameter, and embedded in a SiO2 film. It was placed at the bottom of a microfluidic channel against a macroscopic indium tin oxide (ITO) top electrode, forming a DEP device in “points-and-lid” configuration. We have shown that E. coli DHα5 cells flowing through the channel can be effectively captured and concentrated at the desired microscale areas inside the channel using a small AC voltage (~6-10 Vpp). This device is particularly effective in capturing viral particles (such as bacteriophage T4r) due to the comparable size between the viral particles and the exposed VACNF tip. To achieve specific detection, the DEP chip has been integrated with a Raman probe for SERS measurements of nanotag-labelled E. coli DHα5 cells. The SERS nanotags are based on iron oxide-gold (IO-Au) core-shell nanoovals (NOVs) of ~50 nm in size, which are coated with QSY21 Raman reporters and attached to E. coli cells through specific antibodies. The combination of the greatly enhanced Raman signal by the SERS nanotags and the effective DEP concentration significantly improves the detection limit and speed. The SERS signal has been fully validated with fluorescence microscopy measurements under all DEP conditions. A concentration detection limit as low as 210 cfu/mL using a portable Raman system has been obtained with a DEP capture time of only ~50 s. The detection has been validated in purified solutions as well as complex samples including chicken broth, soil solution and apple juice. Real-time impedance measurements has also been demonstrated as a feedback during DEP capture of vaccinia viral particles. By controlling the proper AC voltage, the nucleic acid contents in the viral particles can be released by opening the envelope with electroporation under the high electric field at the VACNF tips. These results demonstrate the potential to develop a compact portable system for rapid and highly sensitive detection of specific pathogens. Furthermore, this technique is based on physical method and the pathogenic particles are fully released after the AC voltage is turned off, making it a robust device that can be repeatedly used.

Raman rapid detection of environmental hormone

Diethylhexyl phthalate(DEHP) is a kind of plasticizer，which is regarded as environmental hormone due to reproductive toxicity to human body and also has the risk of breast cancer, endometrial cancer and liver cancer after long-term intake. In this work, a rapid surface enhanced Raman scattering (SERS) technique to detect the DEHP residue level in food products is developed by optimizing the synthesis of a hexakisphosphate (IP6) stabilized Au@Ag@IP6 nanoparticles. For further improvement of detection sensitivity, such SERS substrate is treated by using 1-dodecanethiol (DT) to enable its capability of capturing more DEHP molecules into the vicinity of SERS hot spots. Au@Ag@IP6/DT-based Raman protocol could analyze DEHP down to 10−8 M. By using a portable Raman system, the simple and reliable SERS method is used to on-site determine trace DEHP in real sample of energy drinks, which meets the requirement of national standard.

Ion inducing surface interaction for improved SERS detection of melamine in fertilizer and soil

AbstractUltra‐sensitive platform for surface‐enhanced Raman scattering detecting trace melamine is constructed by adding Fe3+ ions. In this work, first, inositol hexaphosphate (IP6) micelle capped silver nanoparticles (IP6@AgNPs) is synthesized. Taking advantage of the strong interaction of Fe3+ and IP6 micelle, surface‐enhanced Raman scattering activity of IP6@AgNPs could be improved by formation of more “hot spots” induced by rational addition of due amount Fe3+. Second, IP6@AgNPs binding Fe3+ could offer the anchoring sites to capture melamine molecules due to containing NH group and/or N atom. Such Fe3+ acted as dual functions is beneficial to elevating sensitivity of determining trace melamine in water, fertilizer, and soil samples with the limits of detection about 1.26, 1.26, and 63.0 ppb, respectively. This proposed assay based on a portable Raman system could monitor real samples without complicated pretreatment, which is perspective to inspect trace melamine on‐field in water and soil environment.

Highly Sensitive Magnetic-SERS Dual-Function Silica Nanoprobes for Effective On-Site Organic Chemical Detection.

We report magnetic silver nanoshells (M-AgNSs) that have both magnetic and SERS properties for SERS-based detection. The M-AgNSs are composed of hundreds of Fe3O4 nanoparticles for rapid accumulation and bumpy silver shell for sensitive SERS detection by near-infrared laser excitation. The intensity of the SERS signal from the M-AgNSs was strong enough to provide single particle-level detection. We obtained much stronger SERS signal intensity from the aggregated M-AgNSs than from the non-aggregated AgNSs. 4-Fluorothiophenol was detected at concentrations as low as 1 nM, which corresponds to 0.16 ppb. The limit of detection for tetramethylthiuram disulfide was 10 μM, which corresponds to 3 ppm. The M-AgNSs can be used to detect trace amounts of organic molecules using a portable Raman system.

Resonance Raman detection of antioxidants using an iron oxide nanoparticle catalysed decolourisation assay

Nanozymes are metal nanoparticles with catalytic properties that can be used to oxidise peroxidase substrates giving a colorimetric response which can be detected using UV-vis, and recently, Raman spectroscopy. Due to their ease of synthesis and increased stability, nanozymes are being increasing investigated to replace conventional enzymes for the detection of biomolecules. Here we exploit the catalytic activity of iron oxide (Fe2O3) nanoparticles combined with the substrate 2,2-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) in a decolourisation assay for the detection of antioxidants. Fe2O3 nanoparticles were used to catalyse the oxidation of ABTS to its green radical cation which, upon the addition of an antioxidant, resulted in a decolourisation due to the reduction of the radical cation caused by the hydrogen donating antioxidant. The assay was applied for the detection of multiple antioxidants (glutathione, chlorogenic acid and ascorbic acid), and was followed by monitoring the resonance Raman scattering from the ABTS solution using a portable Raman system with 785 nm laser excitation. This novel assay has the potential to be optimised to detect antioxidant activity in body fluid with low limits of detection with point of use monitoring.

Heterostructured cube Au–Ag composites for rapid Raman detection of antibiotic ciprofloxacin

Abuse of synthetic antibiotic ciprofloxacin (CIP) caused the diffuse of drug resistant or even multidrug‐resistant pathogen strains. It called for a rapid technique to detect the CIP residue level in food products and environment. Highly sensitive surface enhanced Raman spectroscopy (SERS) offering intrinsic fingerprint information of molecule could be developed to become a quick method for detecting trace targeted species. In this work, the inositol hexakisphosphate as a stabilizing agent can be also used to synthesize Au–Ag bimetal heterostructured cubes. Heterostructured cubes were employed as highly active SERS substrate, and based on a portable Raman system, a simple and reliable SERS method was proposed for direct detection of trace CIP in water and chicken wings. Limits of detection of CIP in water and chicken wings were 8 × 10−8 and 2 × 10−7 M respectively. Copyright © 2016 John Wiley & Sons, Ltd.

Remote Raman measurements of minerals, organics, and inorganics at 430 m range.

Raman spectroscopy is a characterization technique that is able to analyze and detect water or water-bearing minerals, minerals, and organic materials that are of special interest for planetary science. Using a portable pulsed remote Raman system with a commercial 8in. (203.2mm) telescope, a frequency doubled Nd-YAG-pulsed laser, and a spectrometer equipped with an intensified CCD camera, we acquired good quality Raman spectra of various materials from a 430m standoff distance during daylight with detection times of 1-10s, in a realistic context in which both the exciting source and the detector are part of the same measurement system. Remote Raman spectra at this distance provided unambiguous detection of compounds such as water and water ice, dry ice, sulfur, sulfates, various minerals and organics, and atmospheric gases. This research work demonstrates significant improvement in the remote Raman technique as well as its suitability for solar system exploration.

Study of corrosion in archaeological gilded irons by Raman imaging and a coupled scanning electron microscope-Raman system.

In this work, analytical and chemical imaging tools have been applied to the study of a gilded spur found in the medieval necropolis of Erenozar (Bizkaia, Spain). As a first step, a lot of portable equipment has been used to study the object in a non-invasive way. The hand-held energy-dispersive X-ray fluorescence equipment allowed us to characterize the artefact as a rare example of an iron matrix item decorated by means of a fire gilding technique. On the other hand, the use of a portable Raman system helped us to detect the main degradation compounds affecting the spur. Afterwards, further information was acquired in the laboratory by analysing detached fragments. The molecular images obtained using confocal Raman microscopy permitted us to characterize the stratigraphic succession of iron corrosions. Furthermore, the combined use of this technique with a scanning electron microscope (SEM) was achieved owing to the use of a structural and chemical analyser interface. In this way, the molecular characterization, enhanced by the magnification feature of the SEM, allowed us to identify several micrometric degradation compounds. Finally, the effectiveness of one of the most used desalination baths (NaOH) was evaluated by comparing its effects with those provided by a reference bath (MilliQ). The comparison proved that basic treatment avoided any side effects on the spur decorated by fire gilding, compensating for the lack of bibliographic documentation in this field.This article is part of the themed issue 'Raman spectroscopy in art and archaeology'.

Surface enhanced Raman spectroscopy (SERS) as a method for the toxicological analysis of synthetic cannabinoids

Synthetic cannabinoids (K2, spice) present problems in forensic investigations because standard presumptive methods, such as immunoassays, are insufficiently specific for the wide range of potential target compounds. This issue can lead to problems with low sensitivity and yield false negative results. A potential solution to this problem is surface enhanced Raman spectroscopy (SERS).In this study we demonstrate the analysis of a set of structurally similar synthetic cannabinoids using SERS. The procedure involves mixing the analyte with gold nanoparticles prepared in a solution containing alkali or alkaline earth salt solutions. The salts produce aggregation of the nanoparticles with a resultant spectral enhancement due to the formation of spectral hotspots with enhanced field effects within the aggregate. Among the salts tested, 0.0167M MgCl2 produced the lowest limit of detection and best overall sensitivity. The method produces clearly distinguishable spectra for each synthetic cannabinoid with detection limits as low as 18ng/mL. Spiked urine samples were also analyzed following a cleanup procedure involving support liquid extraction. When using a portable Raman system, a higher concentration of MgCl2 was needed to produce similar a LOD. The results demonstrate that this procedure has great potential as a method for presumptive screening of synthetic cannabinoids.

Screening for Adulterants in Liquid Milk Using a Portable Raman Miniature Spectrometer with Immersion Probe.

A portable Raman system with an immersion fiber optic probe was assessed for point-of-collection screening for the presence of adulterants in liquid milk. N-rich adulterants and sucrose were measured in this proof-of-concept demonstration. Reproducibility, limit of detection range and other figures of merit such as specificity, sensitivity, ratio of predicted to standard deviation, standard error of prediction and root mean squared error for cross validation were determined from partial least squares (PLS) and partial least squares with discriminant analysis (PLS-DA) calibrations of milk mixtures containing 50-1000 ppm (parts per million) of melamine, ammonium sulphate, Dicyandiamide, urea and sucrose. The spectra were recorded by immersing the fiber optic probe directly in the milk solutions. Despite the high scattering background which was easily and reliably estimated and subtracted, the reproducibility for four N-rich compounds averaged to 11% residual standard deviation (RSD) and to 5% RSD for sucrose. PLS calibration models predicted the concentrations of separate validation sets with standard errors of prediction of between 44 and 76 ppm for the four N-rich compounds and 0.17% for sucrose. The sensitivity and specificity of the PLS-DA calibration were 92% and 89%, respectively. The study shows promise for use of portable mini Raman systems for routine rapid point-of-collection screening of liquid milk for the presence of adulterants, without the need for sample preparation or addition of chemicals.

The effect of irradiance and integration time in in vivo normal skin Raman measurements assessed by multivariate statistical analysis

BACKGROUND: The successful discrimination of the subtle spectral characteristics of human skin in Raman spectra requires optimal acquisition parameters. We explore the translational momentum of Raman spectroscopy towards clinical practice by fine-tuning two basic experimental parameters (irradiance and integration time) of a portable Raman system used in skin measurements. OBJECTIVE: The aim of this study is to construct a generic protocol for recording the optimal Raman signal for in vivo skin measurements. METHODS: In vivo spectra were collected from two individuals of normal Fitzpatrick type III skin type. We assessed two different irradiation setups with three different integration times each by separating the raw signal from the noise using multivariate analysis. RESULTS: Our results showed that under a time threshold no optimal measurement conditions can be achieved. On the other hand, increased laser power and acquisition time do not offer a significant advantage over the selected lower values. Baseline correction is the most critical component for analysing normalized skin Raman spectra. CONCLUSIONS: A simple working protocol based on multivariate statistics offers the relative adjustment of irradiance and signal integration time among other experimental parameters that must be examined for optimal Raman measurements of skin.

Assessment of tenderness of aged bovine gluteus medius muscles using Raman spectroscopy

A portable 671nm Raman system was evaluated as a rapid and non-destructive device for the assessment of beef tenderness using 175 gluteus medius muscles (99 for calibration, 76 for validation) aged at −1°C and 7°C for fourteen days. Raman and shear force (SF) measurements were performed with the aged beef. The samples stored at −1°C showed on average only slightly increased SF values. The correlation of Raman spectra with SF using partial least squares regression yielded cross-validated predictions of SF for both storage temperatures with coefficients of determination R2cv=0.33–0.79. Validation with independent samples resulted in predictions with R2val=0.33. Using thresholds between 30 and 49N, tough and tender samples could be discriminated with partial least squares discriminant analysis with 70–88% and 59–80% accuracy during cross-validation and validation, respectively. These results demonstrate the principle feasibility to predict the SF and thus toughness of raw, aged gluteus beef cuts with a portable Raman device showing potential for grading beef cuts.

Nondestructive detection of the freshness of fruits and vegetables using gold and silver nanoparticle mediated graphene enhanced Raman spectroscopy

Raman spectroscopy and surface enhanced Raman spectroscopy (SERS) are expanding their horizons into widespread applications as analytical tools with immense potentials. In the current work, we demonstrated the use of a portable Raman system conjugated with graphene enhanced Raman spectroscopy (GERS) for assessing the freshness of fruits and vegetables. Dual nano-platforms have been used involving the use of gold/silver nanoparticles seeded graphene sheets (Au@G and Ag@G, respectively) as the SERS system for probing the freshness of fruits and vegetables. The data showed that Au@G offered high sensitivity, high resolution and high biocompatibility. A novel and simple GERS method based on a microdrop of Ag@G or Au@G on the fruit surface was used for the evaluation of the freshness of the fruits/vegetables. Fruits and vegetables like Wax apple, Lemon, Tomato, Red Pepper and Carrot were investigated. Market fresh and refrigerated fruits and vegetables were probed at various time intervals ranging from 1 day to 2 weeks. The results signify that some of the Raman signals increase with storage and certain peaks were found to appear with long term storage in the refrigerator. This study demonstrates that the quality of fruits and vegetables under short term (1 week) and even under cold storage conditions are impacted and should be avoided as much as possible. The changes effected on the fruits and vegetables under refrigeration and the applicability of using Au@G enabled GERS as a successful and novel platform for assessing the freshness of fruits and vegetables is elaborated.

Integration of Nanostructured Dielectrophoretic Device and Surface-Enhanced Raman Probe for Highly Sensitive and Rapid Pathogen Detection

Rapid and highly sensitive is critical for food safety and environmental protection. To achieve this, it requires the combination of both novel sample handling techniques and extremely sensitive detection methods. In previous studies, we have demonstrated the effective capture and quick concentration of pathogenic particles such as viral and bacterial particles in a fluidic chip using dielectrophoresis (DEP) enhanced with the highly focused electric field at the tip of an embedded nanoelectrode array. This work reports a further development with a synergistic approach to the concentration, detection and kinetic monitoring of pathogens through the integration of the nanostructured DEP device with nanotag-labelled Surface Enhanced Raman Scattering (SERS) for specific bacterial identification. A nanoelectrode array made of embedded Vertically Aligned Carbon Nanofibers (VACNFs) at the bottom of a microfluidic chip is used to effectively capture and concentrate nanotag-labelled E. coli DHα5 cells into a 200 micron x 200 micron area at which the Raman laser probe is focused. The SERS nanotags are based on iron oxide-gold (IO-Au) core-shell nanoovals (NOVs) of ~50 nm in size, which are coated with QSY21 Raman reporters and attached to E. coli cells through specific antibodies. The combination of the greatly enhanced Raman signal by the SERS nanotags and the effective DEP concentration significantly improves the detection limit and speed. The SERS signal has been measured with both a confocal Raman microscope and a portable Raman probe during DEP capture, and has been fully validated with fluorescence microscopy measurements under all DEP conditions. The SERS measurements are sensitive enough to detect a single bacterium. A concentration detection limit as low as 210 cfu/mL using a portable Raman system has been obtained with a DEP capture time of only ~50 s. The detection has been validated in purified solutions as well as complex samples including chicken broth, soil solution and apple juice. These results demonstrate the potential to develop a compact portable system for rapid and highly sensitive detection of specific pathogens. Furthermore, the AC impedance can be used to monitor the pathogen capture with slightly higher detection limit. Such system is reusable, requires minimum sample preparation, and is ideal for field applications.