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Phenotypic and Metabolic Profiling of Biological Samples in Near Real-Time Using Raman SpectroscopyZu, Theresah Nom Korbieh 22 October 2014 (has links)
Raman spectroscopy, together with multivariate statistical analyses, has proven to be a near real-time analytical technique capable of phenotyping cells, tissues and organs. This dissertation will show exclusively the application of the Raman spectroscopy phenotypic profiling method to; (i) microbial toxicity, (ii) ex-vivo organ perfusion, and (iii) subcellular location targeting.
Real-time analytical methods for monitoring living biological systems will enable study of the physiological changes associated with growth, genetic manipulations, and adverse environmental conditions. Most existing analytical methods (NMR exempt), though highly accurate, must be performed off-line and most require destruction of the studied sample. These attributes make these methodologies less desirable to the study of physiological changes of cells, tissues, and organs. In this work, Raman spectroscopy has been identified and shown to be a good candidate for real-time analysis mainly because it can be performed: (i) in near real-time, (ii) non-destructively and with minimal sample preparation, (iii) through a glass barrier (i.e., can be performed in situ), and (iv) with minimal spectral interference from water. Here, Raman spectroscopy was used in combination with multivariate statistics to analyze the differing toxic effects of 4-C chain alcohols on E. coli. Good correlations were established between Raman spectra and off-line analytical techniques used to measure: (i) saturated, unsaturated, and cyclopropane fatty acids; (ii) amino acid composition of total protein; and (iii) cell membrane fluidity. Also, Raman 'fingerprint' analysis was used to discriminate among different phenotypic responses of cells. In addition, this methodology was applied to analyze perfusates of organs maintained by the VasoWave® organ perfusion system. Raman fingerprints can be used to assess organ health, and it is believed this data can be used to inform decisions such as whether or not to transplant an organ.
Finally, molecular biology techniques were used to design and produce specific protein targets harboring a silver binding domain fusion, which upon release migrate to specific subcellular locations. By employing the related technique of surface-enhanced Raman scattering (SERS), which produces a highly amplified Raman signal in the presence of metallic nanoparticle substrates (e.g., silver nanoparticles), different regions of the E. coli cell structure were studied. The target regions studied by the technique included: (i) outer cell membrane, (ii) periplasm, and the (iii) cytoplasm. / Ph. D.
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Advanced Applications of Raman Spectroscopy for Environmental AnalysesLahr, Rebecca Halvorson 09 January 2014 (has links)
Due to an ever-increasing global population and limited resource availability, there is a constant need for detection of both natural and anthropogenic hazards in water, air, food, and material goods. Traditionally a different instrument would be used to detect each class of contaminant, often after a concentration or separation protocol to extract the analyte from its matrix. Raman spectroscopy is unique in its ability to detect organic or inorganic, airborne or waterborne, and embedded or adsorbed analytes within environmental systems. This ability comes from the inherent abilities of the Raman spectrometer combined with concentration, separation, and signal enhancement provided by drop coating deposition Raman (DCDR) and surface-enhanced Raman spectroscopy (SERS).
Herein the capacity of DCDR to differentiate between cyanotoxin variants in aqueous solutions was demonstrated using principal component analysis (PCA) to statistically demonstrate spectral differentiation. A set of rules was outlined based on Raman peak ratios to allow an inexperienced user to determine the toxin variant identity from its Raman spectrum. DCDR was also employed for microcystin-LR (MC-LR) detection in environmental waters at environmentally relevant concentrations, after pre-concentration with solid-phase extraction (SPE). In a cellulose matrix, SERS and normal Raman spectral imaging revealed nanoparticle transport and deposition patterns, illustrating that nanoparticle surface coating dictated the observed transport properties. Both SERS spectral imaging and insight into analyte transport in wax-printed paper microfluidic channels will ultimately be useful for microfluidic paper-based analytical device (𝜇PAD) development. Within algal cells, SERS produced 3D cellular images in the presence of intracellularly biosynthesized gold nanoparticles (AuNP), documenting in detail the molecular vibrations of biomolecules at the AuNP surfaces. Molecules involved in nanoparticle biosynthesis were identified at AuNP surfaces within algal cells, thus aiding in mechanism elucidation.
The capabilities of Raman spectroscopy are endless, especially in light of SERS tag design, coordinating detection of analytes that do not inherently produce strong Raman vibrations. The increase in portable Raman spectrometer availability will only facilitate cheaper, more frequent application of Raman spectrometry both in the field and the lab. The tremendous detection power of the Raman spectrometer cannot be ignored. / Ph. D.
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Visualization, Characterization, and Analysis of Gold Nanoparticles Fate and Transport in Aqueous Porous Media Environment with Advanced Photonics TechniqueChan, Matthew Yunho 27 April 2017 (has links)
Increased proliferation of nanotechnology has led to concerns regarding its implication to the water environment. Gold nanoparticles (AuNP) were used as a model nanomaterial to investigate the fate and dynamics of nanoparticles in the complex water environment. A column study was performed to examine the fate and transport of gold nanoparticles with two different coatings in porous media. The resulting data suggested that gold nanoparticles aggregate significantly in the porespace of the column interior, a finding that is not predicted by traditional colloidal filtration theory or Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Surface-enhanced Raman spectroscopy (SERS) was developed as a new technique to investigate AuNP aggregation in water with varying salt levels. The SERS technique proved valuable as an analytical technique, elucidating information about aggregation as well as AuNP surface interactions with dissolved halides in water. A thorough investigation examining Aunt aggregation with monovalent and divalent salts utilizing SERS, ultraviolet-visible light (UV-Vis) spectroscopy, and dynamic light scattering (DLS) was conducted. Each technique provided data describing different aspects of the dynamic behavior of AuNPs in complex water environments. Results suggest that in addition to attractive and repulsive interactions described by DLVO theory, chemical interactions between the AuNP surface and dissolved halides were also a significant driving force for aggregation and other transformative behaviors of AuNPs in water. The SERS technique developed in this work was shown to be a viable tool to help unveil the vastly complex dynamics of nanomaterial in the water environment. / Ph. D.
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Development of a Temperature Controlled Cell for Surface Enhanced Raman Spectroscopy for in situ Detection of GasesAppelblad, André January 2014 (has links)
This work describes a master’s thesis in engineering physics at Umeå University carried out during the spring semester of 2014. In the thesis the student has constructed and tested a temperature controlled cell for cooling/heating of surface-enhanced-Raman-spectroscopy (SERS) substrates for rapid detection of volatile substances. The thesis was carried out at the Swedish Defence Research Agency (FOI) in Umeå, Sweden. A Linkam Scientific Instruments TS1500 cell was equipped with a Peltier element for cooling/heating and a thermistor temperature sensor. A control system was constructed, based on an Arduino Uno microcontroller board and a pulse-width-modulated (PWM) H-bridge motor driver to control the Peltier element using a proportional-integral (PI) control algorithm. The temperature controlled cell was able to regulate the temperature of a SERS substrate within -15 to +110 °C and maintain the temperature over prolonged periods at ±0.22 °C of the set point temperature. Gas phase of 2-chloro-2-(difluoromethoxy)-1,1,1-trifluoro-ethane (isoflurane) was flowed through the cell and SERS spectra were collected at different temperatures and concentrations. This test showed that the signal is increased when the substrate is cooled and reversibly decreased when the substrate was heated. Keywords: temperature control, Raman scattering, surface enhanced Raman spectroscopy SERS, SERS substrate, volatile substances, Peltier module, thermistor, PWM, H-bridge, PI(D) control. / Detta dokument beskriver ett examensarbete för civilingenjörsexamen i teknisk fysik vid Umeå Universitet som utförts under vårterminen 2014. I examensarbetet har en kyl-/värmecell för temperaturkontroll av substratytor för ytförstärkt ramanspektroskopi (SERS) för snabb detektion av farliga flyktiga ämnen konstruerats och testats. Arbetet utfördes vid Totalförsvarets forskningsinstitut (FOI) i Umeå, Sverige. Utgångspunkten var ett Linkam Scientific Instruments TS1500 mikroskopsteg, vilket utrustades med ett Peltierelement för kylning/värmning och en termistor för temperaturövervakning. Ett styrsystem baserat på ett Arduino Uno mikrostyrenhetskort konstruerades med ett motordrivkort (H-brygga) vilket använder pulsbreddsmodulering (PWM) för att reglera spänningen till Peltierelementet utifrån en PI-regulator. Den färdiga cellen klarade att reglera temperaturen på ett SERS-substrat i ett temperaturspann på ungefär -15 till +110 °C med en temperaturstabilitet på ±0.22 °C av måltemperaturen. Cellen testades sedan på flyktiga ämnen för att visa dess funktion. Difluorometyl-2,2,2-trifluoro-1-kloroetyleter (isofluran) i gasfas, med instrumentluft som bärargas, flödades genom cellen och SERS-spektra erhölls vid olika koncentrationer och temperaturer. Vid samtliga koncentrationer visades att lägre temperatur ger ökad signalstyrka. När ytan sedan värmdes upp sjönk signalen reversibelt tillbaka till ursprungsvärdet. Nyckelord: temperaturkontroll, ytförstärkt ramanspektroskopi, SERS, flyktiga ämnen, Peltierelement, thermistor, PWM, H-brygga, PI(D)-regulator.
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Surface- and tip-enhanced resonant Raman scattering from CdSe nanocrystalsSheremet, E., Milekhin, A. G., Rodriguez, R. D., Weiss, T., Nesterov, M., Rodyakina, E. E., Gordan, O. D., Sveshnikova, L. L., Duda, T. A., Gridchin, V. A., Dzhagan, V. M., Hietschold, M., Zahn, D. R. T. 27 February 2015 (has links) (PDF)
Surface- and tip-enhanced resonant Raman scattering (resonant SERS and TERS) by optical phonons in a monolayer of CdSe quantum dots (QDs) is demonstrated. The SERS enhancement was achieved by employing plasmonically active substrates consisting of gold arrays with varying nanocluster diameters prepared by electron-beam lithography. The magnitude of the SERS enhancement depends on the localized surface plasmon resonance (LSPR) energy, which is determined by the structural parameters. The LSPR positions as a function of nanocluster diameter were experimentally determined from spectroscopic micro-ellipsometry, and compared to numerical simulations showing good qualitative agreement. The monolayer of CdSe QDs was deposited by the Langmuir–Blodgett-based technique on the SERS substrates. By tuning the excitation energy close to the band gap of the CdSe QDs and to the LSPR energy, resonant SERS by longitudinal optical (LO) phonons of CdSe QDs was realized. A SERS enhancement factor of 2 × 10<sup>3</sup> was achieved. This allowed the detection of higher order LO modes of CdSe QDs, evidencing the high crystalline quality of QDs. The dependence of LO phonon mode intensity on the size of Au nanoclusters reveals a resonant character, suggesting that the electromagnetic mechanism of the SERS enhancement is dominant. Finally, the resonant TERS spectrum from CdSe QDs was obtained using electrochemically etched gold tips providing an enhancement on the order of 10<sup>4</sup>. This is an important step towards the detection of the phonon spectrum from a single QD. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Design, characterisation and biosensing applications of nanoperiodic plasmonic metamaterials / Conception, caractérisation et applications de métamatériaux nanopériodiques plasmoniques pour biocapteursDanilov, Artem 11 April 2018 (has links)
Cette thèse considère de nouvelles architectures prometteuses des métamatériaux plasmoniques pour biosensing, comprenant: (I) des réseaux périodiques 2D de nanoparticules d'Au, qui peuvent supporter des résonances des réseaux de surface couplées de manière diffractive; (II) Reseaux 3D à base de cristaux plasmoniques du type d'assemblage de bois. Une étude systématique des conditions d'excitation plasmonique, des propriétés et de la sensibilité à l'environnement local dans ces géométries métamatérielles est présentée. On montre que de tels réseaux peuvent combiner une très haute sensibilité spectrale (400 nm / RIU et 2600 nm / RIU, ensemble respectivement) et une sensibilité de phase exceptionnellement élevée (> 105 deg./RIU) et peuvent être utilisés pour améliorer l'état actuel de la technologie de biosensing the-art. Enfin, on propose une méthode de sondage du champ électrique excité par des nanostructures plasmoniques (nanoparticules uniques, dimères). On suppose que cette méthode aidera à concevoir des structures pour SERS (La spectroscopie du type Raman à surface renforcée), qui peut être utilisée comme une chaîne d'information supplémentaire à un biocapteur de transduction optique. / This thesis consideres novel promissing architechtures of plasmonic metamaterial for biosensing, including: (I) 2D periodic arrays of Au nanoparticles, which can support diffractively coupled surface lattice resonances; (II) 3D periodic arrays based on woodpile-assembly plasmonic crystals, which can support novel delocalized plasmonic modes over 3D structure. A systematic study of conditions of plasmon excitation, properties and sensitivity to local environment is presented. It is shown that such arrays can combine very high spectral sensitivity (400nm/RIU and 2600 nm/RIU, respectively) and exceptionally high phase sensitivity (> 105 deg./RIU) and can be used for the improvement of current state-of-the-art biosensing technology. Finally, a method for probing electric field excited by plasmonic nanostructures (single nanoparticles, dimers) is proposed. It is implied that this method will help to design structures for SERS, which will later be used as an additional informational channel for biosensing.
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Application of Raman and Fluorescence Spectroscopy to Single Chromatographic BeadsLarsson, Mina January 2005 (has links)
<p>Chromatography is a powerful technique, essential in chemical analyses and preparative separation in industry and research. Many different kinds of chromatographic material are needed, due to the large variety of applications. Detailed methods of characterisation are needed to design new chromatographic materials and understand their properties. In this thesis, confocal Raman spectroscopy and surface enhanced Raman spectroscopy (SERS) have been applied to micrometer-size chromatographic beads, for which these techniques have not been used earlier. New methodology, optimized for use with the chromatographic beads, has been developed and evaluated. </p><p>Confocal spectroscopy has been used to determine distributions of functional groups within single chromatographic beads. This distribution is of great importance in determining the chromatographic properties, since the material is porous and the solute molecules can diffuse inside the beads. Most of the confocal experiments have been performed with Raman spectroscopy; fluorescence spectroscopy, using Nd<sup>3+</sup> ions or dye-labelled proteins as fluorescence probes, has been used for comparison. </p><p>The concentration of adsorbed analytes is very low within the beads. SERS was therefore used to enhance the Raman signal. SERS-active surfaces were prepared by incorporating gold nano-particles into the interior of the bead. TEM measurements showed that the gold nano-particles could be observed throughout, and it was possible to record analyte spectra from different positions within the bead. Enhanced spectra could be obtained both for small test molecules and for larger bio-molecules, although the spectra for the smaller analytes were much more intense.</p>
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Application of Raman and Fluorescence Spectroscopy to Single Chromatographic BeadsLarsson, Mina January 2005 (has links)
Chromatography is a powerful technique, essential in chemical analyses and preparative separation in industry and research. Many different kinds of chromatographic material are needed, due to the large variety of applications. Detailed methods of characterisation are needed to design new chromatographic materials and understand their properties. In this thesis, confocal Raman spectroscopy and surface enhanced Raman spectroscopy (SERS) have been applied to micrometer-size chromatographic beads, for which these techniques have not been used earlier. New methodology, optimized for use with the chromatographic beads, has been developed and evaluated. Confocal spectroscopy has been used to determine distributions of functional groups within single chromatographic beads. This distribution is of great importance in determining the chromatographic properties, since the material is porous and the solute molecules can diffuse inside the beads. Most of the confocal experiments have been performed with Raman spectroscopy; fluorescence spectroscopy, using Nd3+ ions or dye-labelled proteins as fluorescence probes, has been used for comparison. The concentration of adsorbed analytes is very low within the beads. SERS was therefore used to enhance the Raman signal. SERS-active surfaces were prepared by incorporating gold nano-particles into the interior of the bead. TEM measurements showed that the gold nano-particles could be observed throughout, and it was possible to record analyte spectra from different positions within the bead. Enhanced spectra could be obtained both for small test molecules and for larger bio-molecules, although the spectra for the smaller analytes were much more intense.
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Spectroelectrochemistry of self-assembled monolayers of 2- and 4-mercaptopyridinesHassan, Nazly 10 July 2007 (has links) (PDF)
Die Elektrochemie und die Spektroelektrochemie von selbst-organisiererten Monoschichten (selfassembled
monolayers, SAMs) gebildet aus 2-Mercaptopyridin (2MP) und 4-Mercaptopyridin
(4MP) wurden an polykristallinen Goldelektroden in wässrigen Elektrolytlösungen untersucht.
Folgende Untersuchungsmethoden wurden angewandt: zyklische Voltammetrie, elektrochemische
Impedanzmessungen (EIM) und oberflächenverstärkte Raman Streuung (surface-enhanced Raman
scattering, SERS).
Die elektrochemischen Untersuchungen von 2MP und 4MP in wässriger saurer Lösung (0.5 M
H2SO4) zeigten, dass 2MP stärker adsorbiert wird als 4MP aufgrund der Bildung eines S-Au-N Chelates,
wobei die S-Au-Interaktionen bei 4MP stärker sind. Die Bildung eines Chelates im Falle
von 2MP verringert die Wahrscheinlichkeit der Bildung eines Dimers. In sauren Lösungen wird
das N-Atom von 2MP protoniert, was zu einer schwächeren Bindung von 2MP-Molekülen zur
Substratoberfläche führt. Die Ergebnisse der SERS-Untersuchungen stimmen mit den Resultaten
aus der zyklischen Voltammetrie überein. Man erhält eine Au-S-Streckschwingungsbande für
2MP zwischen 225 bis 250 cm-1 bei Abscheidung aus wässriger oder saurer Lösung und für 4MP
bei ca. 263 cm-1 in beiden Lösungen. Die SERS-Experimente ergaben eine senkrechte Orientierung
zur Goldoberfläche sowohl für 2MP als auch für 4MP. Die Thion-Thiol-Tautomerie von 2-
Mercaptopyridinen wurde ebenfalls in Betracht gezogen.
Die Unter- und Überpotentialabscheidung von Kupfer auf einer polykristallinen Goldelektrode in
wässriger 0.1 M Schwefelsäure in An- und Abwesenheit von SAMs von 2- und 4-
Mercaptopyridin wurde mit zyklischer Voltammetrie untersucht. Es zeigte sich, daß bei Vorhandensein
der SAMs die Elektrodeposition von Kupfer verhindert wird, was auf starke Wechselwirkungskräfte
zwischen dem Adsorbat (MP) und der Goldoberfläche zurückzuführen ist. 2MP zeigt
eine grössere Inhibierung, was höchstwahrscheinlich auf die Bildung der Chelatstruktur zurückzuführen
ist. Es wurden ebenso Untersuchungen zum Einfluss von 2MP und 4MP auf die abgeschiedene
Kupfermonolage auf der Goldelektrode durchgeführt. Es zeigte sich, daß die Kupfermonolage
teilweise durch 2MP oder 4MP ersetzt wird.
Die Elektronenaustauschgeschwindigkeit für das Fe2+/Fe3+-Redoxsystem in An- und Abwesenheit
von 2MP- oder 4MP-Monolagen wurde mit zyklischer Voltammetrie und elektrochemischen Impedanzmessungen
(EIM) untersucht. Es stellte sich heraus, dass der Elektronenaustausch höchstwahrscheinlich
über Defektstellen in der Monolage (Pinholes) erfolgt. In einer wässrigen Lösung
verringert 4MP den Elektronenaustausch stärker als 2MP. Da die Packungsdichte bei 4MP größer
ist als bei 2MP ist wahrscheinlich auch die Zahl der Pinholes geringer in der 4MP-Monolage. In
saurer Lösung liegen die N-Atome protoniert vor. Man kann davon ausgehen, dass in saurer Lösung
zwei Prozesse gleichzeitig ablaufen, die für den Elektronenaustausch entscheidend sind. Erstens
kommt es zu einer Abstoßung zwischen der positiv geladenen Monolage und den positiv geladenen
Redoxionen. Und zweitens erfolgt eine Abstoßung zwischen den positiv geladenen Molekülen
der SAMs, was zu einer geringeren Packungsdichte führt. Der Ladungsaustausch wird dominiert
durch den zweiten Effekt.
Mit Hilfe von EIM wurden die Elektronenaustauschgeschwindigkeit und der Bedeckungsgrad bestimmt.
Die korrosionshemmende Wirkung von 2MP und 4MP auf Stahl in 3.5 % wässriger NaCl-Lösung
wurde mit Hilfe der EIM untersucht. 2MP zeigte eine grössere Hemmung als 4MP. / The electrochemistry and spectroelectrochemistry of the self-assembled
monolayers (SAMs) prepared of 2-mercaptopyridine (2MP) and 4-mercaptopyridine
(4MP) dissolved either in water or 0.1 M H2SO4 have been investigated at polycrystalline
gold electrodes in aqueous electrolyte solutions using cyclic voltammetry, electrochemical
impedance measurements (EIM) and surface enhanced Raman spectroscopy
(SERS).
Electrochemical studies of 2MP and 4MP monolayers in aqueous acidic solution
(0.5 M H2SO4) suggest that 2MP is adsorbed more strongly than 4MP due to the
formation of S-Au-N chelate. However, the S-Au bond was found to be stronger in
4MP as compared with 2MP. The formation of the chelate in case of 2MP diminishes
the probability of dimer formation. In the acidic solvent, the N-atom of 2MP molecule
will be protonated leading to a weaker interaction of 2MP molecules with the substrate
surface. The SERS results are in good agreement with the cyclic voltammetry
results. The Au-S stretching band was obtained in the region from 215 to 245 cm-1 for
2MP deposited from water and acidic solvent and around 263 cm-1 for 4MP in both
solvents. The SERS measurements showed also a perpendicular orientation of both
2MP and 4MP on the gold surface. In explaining the SERS results, the thione-thiol
tautomerisations of the mercaptopyridines were also taken into consideration.
The under- and overpotential deposition of copper on a polycrystalline gold
electrode in aqueous 0.1 M sulfuric acid in the presence and in the absence of SAMs
of 2- and 4-mercaptopyridine has been studied using cyclic voltammetry. In general,
the presence of these SAMs has been found to inhibit the electrodeposition process of
copper, suggesting very strong interactions between these adsorbates and the Au surface.
2MP shows a higher degree of inhibition, which is due to a stronger interaction
probably due to the formation of the chelate structure. Studies have also been made of
the influence of mercaptopyridines SAMs on the copper monolayer electrodeposited
on the gold surface. The copper adlayer was found to be partially displaced by 2MP
and 4MP monolayers.
The rate of electron transfer for the Fe3+/2+ redox system on the gold electrode
has been probed in the absence and presence of 2MP and 4MP monolayers by cyclic
voltammetry and electrochemical impedance measurements (EIM). The charge transfer
process was suggested to occur through the defects (pinholes) in the monolayer. In
case of aqueous solvent 4MP decreases the electron transfer reaction stronger than
2MP. Since the packing density for 4MP is higher than that of 2MP the number of
pinholes might be lower in 4MP monolayer. In acidic solvent the N-atoms of the mercaptopyridines
will be protonated. It is proposed that two effects, which exist at the
same time, are responsible for the electron transfer process in acidic solution. First,
there will be a repulsive interaction between the positively charged monolayer and the
positively charged redox probe. Second, there is a repulsion among the positively
charged monolayer molecules that results in a less compact monolayer. The charge
transfer is dominated due to the latter effect. With the EIM the rate of electron transfer
and the surface coverage were determined.
2MP and 4MP were examined as steel corrosion inhibitors in 3.5% aqueous
NaCl solution using EIM. 2MP shows higher inhibition efficiency than 4MP.
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Development of Epidermal Growth Factor Receptor (EGFR) Specific Nanoprobes for Surface Enhanced Raman Spectroscopy (SERS)Lucas, Leanne Jennifer 29 July 2013 (has links)
Novel biocompatible nanoprobes for optical imaging of Epidermal Growth Factor receptor (EGFR) were created. 5 and 18 nm gold nanoparticles (AuNPs) and 5 and 45 nm diameter silver nanoparticles (AgNPs) were conjugated to EGF protein via ?-lipoic acid. AgNPs were not previously attached to EGF. TOF-MS confirms EGF-linker formation. ELISA verifies the linked-EGF activity alone and with EGF-NPs. Core-shell silver-gold nanoparticles (AgAuNPs) gave similar results. TEM staining with uranyl acetate exhibits a bright ring, smaller than EGF, around nanoparticles. Dark field microscopy shows localized, intense cytoplasmic scattering, possibly lipid droplets, in cancer cells incubated with or without nanoprobes. Following injection, mice organs were harvested for EGF-NP immune response determination. Sterilization likely inactivated EGF before ICP-MS. Intense surface enhanced Raman scattering (SERS, 632.8 nm) follows MgSO4 induced EGF-AgNPs aggregation. Pelleted EGF-AgNP tagged cancer cells lack SERS indicative intensity contrast. AgAuNPs could provide increased stability, brighter SERS, and reduced silver biocompatibility concerns.
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