1,741,793 research outputs found
Real Time Dual-Channel Multiplex SERS Ultradetection
No full textSurface-enhanced Raman scattering (SERS) can be combined with microfluidics for rapid multiplex analyte screening. Through combination of the high intensity and complex signals provided by SERS with the flow characteristics of microfluidic channels, we engineered a microdevice that is capable of monitoring various analytes from different sources in real time. Detection limits down to the nM range may allow the generation of a new family of devices for remote, real time monitoring of environmental samples such as natural or waste waters and application to the high-throughput screening of multiple samples in healthcare diagnostics
SERS Background Imaging – a Versatile Tool Towards More Reliable SERS Analytics
No full textSurface-enhanced Raman scattering (SERS) is a highly selective and sensitive straightforward analytical method, which is however not yet established in routine analysis due to a lack of reliability and reproducibility. Here we utilise the broad SERS continuum background (SERS-BG) accompanying every SERS measurement as a versatile tool towards more reliable SERS analytics. We apply a heterogeneous gold SERS substrate immersed with an adenosine triphosphate solution to show that the integrated SERS-BG distinctly correlates with the intensity of the analyte signals in the SERS spectrum. Based on this relationship we introduce an easy-to-handle, automatable and more reliable SERS measurement procedure starting with fast and high-contrast imaging of the SERS substrate followed by hot spot localisation and recording of highly enhanced SERS spectra at the centre of the diffraction-limited spot. We further demonstrate the applicability of SERS-BG imaging by combining it with other optical modalities and electron microscopy to assess structure-property relationships. Additionally, we perform Monte-Carlo simulations to evaluate the sampling error in SERS experiments highlighting the advantages of our method over conventional SERS experiments.</div
Reproducible surface-enhanced Raman quantification of biomarkers in multicomponent mixtures
No full textA.C.D.L. is supported by an AIRC Start-up Grant 11454 and a FIR project RBFR12WAPY. A.D.F. is supported by an EPSRC Career Acceleration Fellowship (EP/I004602/1). D.C. is supported by an AIRC Grant IG10341 and the projects PON01-00117 and PON01-00862. S.M. is supported by a PRIN project 2012CK5RPF_05.Direct and quantitative detection of unlabeled glycerophosphoinositol (GroPIns), an abundant cytosolic phosphoinositide derivative, would allow rapid evaluation of several malignant cell transformations. Here we report label-free analysis of GroPIns via surface-enhanced Raman spectroscopy (SERS) with a sensitivity of 200 nM, well below its apparent concentration in cells. Crucially, our SERS substrates, based on lithographically defined gold nanofeatures, can be used to predict accurately the GroPIns concentration even in multicomponent mixtures, avoiding the preliminary separation of individual compounds. Our results represent a critical step toward the creation of SERS-based biosensor for rapid, label-free, and reproducible detection of specific molecules, overcoming limits of current experimental methods.Peer reviewe
SERS-Active Printable Hydrogel for 3D Cell Culture and Imaging
No full textHydrogel-based three-dimensional
(3D) cell culture systems
mimic
the salient elements of extracellular matrices and promote native
cell function. However, high-resolution 3D cell imaging that can provide
biological information about multiple features of individual cells
is yet to be realized. In this context, we incorporated plasmonic
gold nanoparticles (AuNPs) into an alginate/gelatin hydrogel to produce
surface-enhanced Raman spectroscopy (SERS)-active hydrogel inks for
the 3D printing and culturing of Vero cells. Dense incorporation of
AuNPs enables production of a printed 3D grid structure with 3D SERS
performance, but with no measurable adverse effects on cell growth.
Label-free SERS spectra were collected within a hydrogel, and a random
forest binary classifier was developed to discriminate Vero cell signals
from the hydrogel background with an accuracy of 87.5%. The results
suggest that SERS signals from cellular components, such as proteins,
lipids, and carbohydrates, account for this discrimination. We demonstrate
visualization of cell shape, location, and density by combining predicted
binary maps with peak feature intensity maps in 2D and 3D. SERS images
with a resolution of ≈3 μm match well with the microscopy
images and show clear increases in intensity with incubation time.
We suggest that 3D SERS cell imaging is a promising means to examine
the effect of external cell stimuli on cellular behavior for diagnostic
purposes
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Interactions of single and few organic molecules with SERS hot spots investigated by orientational imaging and super-resolution optical imaging
No full texttextDynamics between organic molecules and surface enhanced Raman scattering (SERS) hot spots are extracted from far-field optical images by two experimental methods presented in this thesis: orientational imaging and super-resolution optical imaging. We introduce SERS orientational imaging as an all-optical technique able to determine the three-dimensional orientations of SERS-active Ag nanoparticle dimers. This is accomplished by observing lobe positions in SERS emission patterns formed by the directional polarization of SERS emission along the longitudinal axis of the dimer. We further extend this technique to discriminate nanoparticle dimers from higher order aggregates by observing the wavelength-dependence of SERS emission patterns, which are unchanged in nanoparticle dimers, but show differences in higher order aggregates involving two or more nanoparticle junctions. Dynamic fluctuations in the SERS emission pattern lobes are observed in aggregates labeled with low dye concentrations, as molecules diffuse into regions of higher electromagnetic enhancement in multiple nanoparticle junctions. In order to investigate these dynamic interactions between single organic molecules and nanoparticle hot spots we present the first super-resolution optical images of single-molecule SERS (SM-SERS), introducing super-resolution imaging as a powerful new tool for SM-SERS studies. Mapping the dynamic movement of SM-SERS centroid positions with +/- 5 nm resolution reveals the position-dependent SERS intensity as the centroid samples different positions in space. We have proposed that the diffusion of the SERS centroid is due to diffusion of a single molecule on the surface of the nanoparticle, which leads to changes in coupling between the scattering dipole and the optical near field of the nanoparticle. Finally, we combine an isotope-edited bi-analyte SERS spectral approach with super-resolution optical imaging and atomic force microscopy (AFM) structural analysis for a more complete picture of molecular dynamics in SERS hot spots. We demonstrate the ability to observe multiple molecule dynamics in a single hot spot and show that in addition to the single-molecule regime, a "few" molecule regime is able to report on position-dependent SERS intensities in a hot spot. Furthermore, we are able to identify multiple local hot spots in single nanoparticle aggregates.Chemistr
Monolayer to MTS : using SEM, HIM, TEM and SERS to compare morphology, nanosensor uptake and redox potential in MCF7 cells
No full textThis research received support from the QNano Project http://www.qnano-ri.eu which is financed by the European Community Research Infrastructures under the FP7 Capacities Programme (Grant No. INFRA-2010-262163), and its partner Trinity College Dublin.Cellular redox potential is important for the control and regulation of a vast number of processes occurring in cells. When the fine redox potential balance within cells is disturbed it can have serious consequences such as the initiation or progression of disease. It is thought that a redox gradient develops in cancer tumours where the peripheral regions are well oxygenated and internal regions, further from vascular blood supply, become starved of oxygen and hypoxic. This makes treatment of these areas more challenging as, for example, radiotherapy relies on the presence of oxygen. Currently techniques for quantitative analysis of redox gradients are limited. Surface enhanced Raman scattering (SERS) nanosensors (NS) have been used to detect redox potential in a quantitative manner in monolayer cultured cells with many advantages over other techniques. This technique has considerable potential for use in multicellular tumour spheroids (MTS) - a three dimensional (3D) cell model which better mimics the tumour environment and gradients that develop. MTS are a more realistic model of the in vivo cellular morphology and environment and are becoming an increasingly popular in vitro model, replacing traditional monolayer culture. Imaging techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM) and helium ion microscopy (HIM) were used to investigate differences in morphology and NS uptake in monolayer culture compared to MTS. After confirming NS uptake, the first SERS measurements revealing quantitative information on redox potential in MTS were performed
Study of merocyanine photoacidity by SERS technique
No full textopenLe specie molecolari che subiscono reversibilmente la dissociazione dei protoni acidi in seguito a
stimolazione elettromagnetica (i.e. luminosa) vengono chiamate “fotoacidi”. Questo controllo remoto
dei loro equilibri acido/base potrebbe fornire un modo per trasformare l’energia luminosa in altri tipi
di energia. In questo senso, le merocianine, un fotoacido sotto studio da pochi anni, risultano essere
ottimi candidati, riuscendo a produrre alte concentrazioni di protoni con alta efficienza e buona
reversibilità in soluzione acquosa, non acquosa, ed altresì quando inglobato in materiali polimerici.
Non meno importante, le merocianine mostrano attività con lunghezze d’onda tipiche dello spettro
visibile.
Scopo di questa tesi è approfondire l’evoluzione e la cinetica di questa specie in soluzione acquosa,
tramite l’utilizzo della spettroscopia Raman e della tecnica SERS
SERS-Active Composites with AuAg Janus Nanoparticles/Perovskite in Immunoassays for Staphylococcus aureus Enterotoxins
No full textThe accurate detection of Staphylococcus aureus enterotoxins (SEs) is vital
for food safety owing to their high
pathogenicity, which may be performed with surface-enhanced Raman
scattering (SERS) if SERS-active nanostructures are used. Herein,
a Au–Ag Janus nanoparticle (NPs)/perovskite composite-engineered
SERS immunoassay was developed for SEC detection. Plasmonic Au–Ag
Janus NPs demonstrated inherent SERS activity from the 2-mercaptobenzoimidazole-5-carboxylic
acid ligands. CsPbBr3@mesoporous silica nanomaterials (MSNs)
were prepared and transformed into CsPb2Br5@MSNs
in the aqueous phase. Paired SEC antibody–antigen-driven plasmonic
Au–Ag Janus NP-CsPb2Br5@MSN composites
were prepared. They showed amplified SERS activity, attributed to
the depressed plasmonic decay due to electromagnetic field enhancement
and the electron transfer mechanism. A positive relationship was established
between SERS signals of composites and the SEC concentration. An additive-free
SERS immunoassay was developed for simple, sensitive, and reproducible
SEC detection. This study will be extended to develop multiple additive-free
SERS-active plasmonic NP/perovskite composites that will open up the
possibility of exploring more SERS detection probes for food safety
monitoring
SERS-based DNA Sensors Using Morpholino Oligos
No full textIn this study we compare binding efficiencies of morpholino probes under 1.0M and 0.01M salt concentrations and examine DSNB-conjugated gold nanoparticles with silica-coated magnetic nanoparticles for use in SERS-based nucleic acid biosensors using morpholinos. Advancements in Surface Enhanced Raman Spectroscopy (SERS) have made possible devices capable of sensing a particular sequence of DNA in minutes. Applications of these devices include rapid identification of disease, possibly before symptoms arise. If practical use of such sensors is obtained, many false diagnoses could potentially be avoided. Equimolar solutions of target DNA and morpholino probes were prepared and biding efficiencies of morpholino-DNA were compared. Conjugated Gold and magnetic nanoparticles were exposed to two sequences of DNA; one being the target West Nile Virus (WNV) DNA and the other being Blue Tongue Virus DNA. Both DNA solutions were analyzed using SERS spectroscopy. We found that morpholino probes bind more efficiently at low salt concentrations. We demonstrated proof of concept of our DNA sensing method; however, future studies will be required to optimize this sensing protocol
NANOPARTICLES WITH SERS EFFECT FOR IDENTIFICATION OF TUMOR CELLS AND PATHOGENS
No full textopenLa spettroscopia Raman potenziata da superfici (SERS) sfrutta la risonanza plasmonica localizzata (LSPR), regolata dalla condizione di Frohlich per l'amplificazione del segnale ottenuta tramite risonanze plasmoniche in nanoparticelle metalliche. Questo meccanismo è impiegato in biomedicina attraverso approcci label-free e label-based (con strutture ingegnerizzate) per la diagnosi e il monitoraggio di patologie. Di particolare rilevanza sono le nanostrutture d'oro, favorite per la loro stabilità e funzionalizzate con agenti di targeting per mirare selettivamente biomarcatori nel sangue. Le prospettive future si concentrano sull'integrazione con l'Intelligenza Artificiale per la creazione di dispositivi portatili con l'obiettivo di trasformare il SERS in uno strumento clinico rapido e affidabile.Surface-enhanced Raman spectroscopy (SERS) exploits localized surface plasmon resonance (LSPR), tuned by the Frohlich condition, for signal amplification obtained through plasmonic resonances in metallic nanoparticles. This mechanism is used in biomedicine through label-free and label-based approaches (with engineered structures) for the diagnosis and monitoring of diseases. Gold nanostructures are particularly significant, favored for their stability and functionalized with targeting agents to selectively target biomarkers in the blood. Future prospects focus on integration with Artificial Intelligence for the creation of portable devices with the aim of transforming SERS into a rapid and reliable clinical tool
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