Plasmon Resonance Spectroscopy Research Articles

A review of spectroscopic probes constructed from aptamer-binding gold/silver nanoparticles or their dimers in environmental pollutants' detection.

The issue of environmental pollutant residues has gained wide public attention all along. Therefore, it is necessary to develop simple, rapid, economical, portable, and sensitive detection techniques, which have become the focus of research in the pollutants detection field. Spectroscopy is one of the most convenient, simple, rapid, and intuitive analytical tools that can provide accurate information, such as ultraviolet spectroscopy, fluorescence spectroscopy, Raman spectroscopy, plasmon resonance spectroscopy, etc. Gold nanoparticles, silver nanoparticles, and their dimers with unique optical properties are commonly used in the construction of spectroscopic probes. As a class of oligonucleotides that can recognize specific target molecules, aptamers also have a strong ability to recognize small-molecule pollutants. The application of aptamer-binding metal nanoparticles in biosensing detection presents significant advantages for instance high sensitivity, good selectivity, and rapid analysis. And many spectroscopic probes constructed by aptamer-binding gold nanoparticles, silver nanoparticles, or their dimers have been successfully demonstrated for detecting pollutants. This review summarizes the progress, advantages, and disadvantages of aptamer sensing techniques constructed by visual colorimetric, fluorescence, Raman, and plasmon resonance spectroscopic probes combining gold/silver nanoparticles or their dimers in the field of pollutants detection, and discusses the prospects and challenges for their future.

Interactions of Ag nanoparticles with humic acid present in surface water

The present paper reports aggregation behaviour of humic acid (HA) in the presence of silver nanoparticles. Aggregation behaviour has been studied from dynamic light scattering (DLS) measurement, in the presence of silver nanoparticle. Silver nanoparticle has been prepared through chemical route and characterized by plasmon resonance spectroscopy. HA used in the study has been characterized by UV–Vis and fluorescence study; its charged state has been evaluated from the study of its interaction with a cationic dye ruthenium bipyridine. It has been found that HA forms small–medium- and large-sized aggregates in the presence of silver nanoparticle as obtained from DLS diameter. The result has been explained in terms of Langmuir–Hinshelwood adsorption model. It has been proposed that hydrogen bonding and hydrophobic interaction play an important role in the formation of aggregates of HA.

Insight into dual fluorescence effects induced by molecular aggregation occurring in membrane model systems containing 1,3,4-thiadiazole derivatives

This work reports on biophysical insights into the excited state intramolecular proton transfer (ESIPT) processes taking place in three 1,3,4-thiadiazole derivatives that served as model compounds, on which electronic absorption, fluorescence, Fourier-transform infrared spectroscopy (FTIR), surface plasmon resonance (SPR) and electrochemical impedance spectroscopy (EIS) studies were performed. The fluorescence spectra recorded in various solvents revealed an interesting dual fluorescence effect. In molecules in their monomeric form, the effect is associated with the ESIPT phenomenon, and may be further enhanced by aggregation-related effects, such as aggregation-induced emissions. Other spectroscopic studies on the selected molecules in a liposomal medium as a model revealed that, in a biomimetic environment, they can exist in both monomeric and aggregated forms. In both cases, however, the effects observed are closely related to the lipid’s main phase transition temperature and the structure of the molecule. Introduction of specific substituents to the phenyl moiety either allows or prevents proton transfer from occurring in the excited state. The hydrophobicity changes in a lipid environment may result in an emergence of specific molecular forms and therefore either facilitate or hinder ESIPT processes. SPR and EIS confirmed the significant hydrophobicity changes in the model lipid systems, while FTIR measurements revealed a notable influence of 1,3,4-thiadiazoles on the fluidity of liposomal membranes. The results obtained clearly show that the thiadiazole derivatives are very good model molecules for studying hydrophobic-hydrophilic environments, and particularly with polymers or liposomes used as drug delivery systems.

Serotonin Promotes Serum Albumin Interaction with the Monomeric Amyloid β Peptide.

Prevention of amyloid β peptide (Aβ) deposition via facilitation of Aβ binding to its natural depot, human serum albumin (HSA), is a promising approach to preclude Alzheimer’s disease (AD) onset and progression. Previously, we demonstrated the ability of natural HSA ligands, fatty acids, to improve the affinity of this protein to monomeric Aβ by a factor of 3 (BBRC, 510(2), 248–253). Using plasmon resonance spectroscopy, we show here that another HSA ligand related to AD pathogenesis, serotonin (SRO), increases the affinity of the Aβ monomer to HSA by a factor of 7/17 for Aβ40/Aβ42, respectively. Meanwhile, the structurally homologous SRO precursor, tryptophan (TRP), does not affect HSA’s affinity to monomeric Aβ, despite slowdown of the association and dissociation processes. Crosslinking with glutaraldehyde and dynamic light scattering experiments reveal that, compared with the TRP-induced effects, SRO binding causes more marked changes in the quaternary structure of HSA. Furthermore, molecular docking reveals distinct structural differences between SRO/TRP complexes with HSA. The disintegration of the serotonergic system during AD pathogenesis may contribute to Aβ release from HSA in the central nervous system due to impairment of the SRO-mediated Aβ trapping by HSA.

Abstract A10: Quantitative biophysical analysis defining key components modulating KRAS recruitment to the plasma membrane

Abstract The KRAS fraction in the plasma membrane (PM) correlates with activation of the MAPK pathway and subsequent cellular proliferation. Understanding KRAS interaction with the PM constitutes a challenge given the complexity of the cellular environment. To gain insight on key components necessary for KRAS signal transduction at the membrane, we make use of reconstituted liposomes and giant unilamellar vesicles as synthetic membranes. Using surface plasmon resonance (SPR) spectroscopy, we demonstrate that KRAS and RAF1 domains interact with these membranes primarily through electrostatic interactions with negatively charged lipids reinforced by additional interactions involving phosphatidyl ethanolamine and cholesterol. RAF1 52-188 (RBDCRD) interacts with the membrane significantly more strongly than the isolated RBD or CRD domains and synergizes KRAS membrane partitioning. Calmodulin and PDE6 delta, but not galectin3, passively sequester KRAS and prevent it from binding to the PM. RAF1 RBDCRD interacts with membranes preferentially at non-raft lipids domains. The carboxyterminal O-methylation is crucial for KRAS membrane localization. These results contribute to a better understanding of how KRAS-membrane interaction can be tuned by multiple factors. Citation Format: Bindu Lakshman, Simon Messing, Eva M. Schmid, Jeffrey D. Clogston, William K. Gillette, Dominic Esposito, Bailey Kessing, Daniel A. Fletcher, Dwight V. Nissley, Frank McCormick, Andrew G. Stephen, Frantz L. Jean-Francois. Quantitative biophysical analysis defining key components modulating KRAS recruitment to the plasma membrane [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr A10.

Use of LSPR Spectroscopy Biosensing for In Situ Identification of Arsenic from Bioleaching of Realgar by Acidithiobacillus ferrooxidans

Localized surface plasmon resonance (LSPR) spectroscopy has received extensive attention as a new method in chemical and biological analysis that can be integrated with nanotechnology. As a new analytical method, LSPR possesses various advantages over the traditional bioanalysis method of enzyme-linked immunosorbent assay (ELISA), including a label-free procedure, low cost, high response speed, simple operation and structure, and ease of storage and transport. Additionally, in situ and high-throughput measurements can be achieved. This study aims to solve the problem of the lack of in situ and highly efficient monitoring methods for current realgar bioleaching processes. An LSPR chip is made to monitor the changes in arsenic content in the process of realgar bioleaching. A convenient, fast, sensitive, and high-throughput method of bioleaching process investigation based on the LSPR spectroscopic in situ monitoring technique is proposed. The LSPR chip provided a highly specific selectivity and a linear detection of arsenic content in the range of 1.0–100.0 μM with detection limit (LOD) 0.898 μM. The developed chip was applied to the quantification of realgar bioleaching sample with satisfactory results.

Metal ion binding and tolerance of bacteria cells in view of sensor applications

Abstract. The biotechnological use of bacterial cells and cell components for the detection and accumulation of valuable substances, such as metals and rare earth elements in aqueous systems, is possible by utilizing innate binding characteristics of microorganisms. We have studied the bacteria cells of Lysinibacillus sphaericus JG-B53 and Sporosarcina ureae ATCC 13881 to assess their potential applicability for the detection of rare earth elements, base metals or precious metals in water. First, we have demonstrated the interactions of the cells with the metal complexes of Au, Ho and Y by studying the color changes of the respective solutions, scanning electron microscopy (SEM) imaging of the metal cluster decoration on the cell surfaces and cell growth tolerance tests. Based on these results, we have developed two potential sensor systems. A colorimetric sensor was established by applying gold nanoparticles (AuNPs) functionalized with surface-layer (S-layer) proteins SslA of S. ureae ATCC 13881 or Slp1 of L. sphaericus JG-B53 for the selective detection of YCl3 up to 1.67 × 10−5 mol L−1 in water. Additionally, a regenerative sensor layer of S-layer proteins on a thin gold film was developed for the detection of 1 × 10−4 mol L−1 YCl3 in water by surface plasmon resonance (SPR) spectroscopy.

Peptide-functionalized iron oxide magnetic nanoparticle for gold mining

Here, we present our work on preparing a novel nanomaterial composed of inorganic binding peptides and magnetic nanoparticles for inorganic mining. Two previously selected and well-characterized gold-binding peptides from cell surface display, AuBP1 and AuBP2, were exploited. This nanomaterial (AuBP-MNP) was designed to fulfill the following two significant functions: the surface conjugated gold-binding peptide will recognize and selectively bind to gold, while the magnetic nano-sized core will respond and migrate according to the applied external magnetic field. This will allow the smart nanomaterial to mine an individual material (gold) from a pool of mixture, without excessive solvent extraction, filtration, and concentration steps. The working efficiency of AuBP-MNP was determined by showing a dramatic reduction of gold nanoparticle colloid concentration, monitored by spectroscopy. The binding kinetics of AuBP-MNP onto the gold surface was determined using surface plasmon resonance (SPR) spectroscopy, which exhibits around 100 times higher binding kinetics than peptides alone. The binding capacity of AuBP-MNP was demonstrated by a bench-top mining test with gold microparticles.Graphical abstract

Enhanced Signal and Quantitative Detection of Anti-Interferon-Gamma Antibody by Using a Nanometer Biolinker.

For rapid screening and quantification of an antisera antibody, a nanometer bithiophene-based conductive biolinker can enhanced signal performance and can be used to verify the interaction of an anti-IFN-γ antibody with an IFN-γ protein. The experimental measurements take a generic approach which takes advantage of the functionality of thiophene-based linkers for biosensors. Effects associated with using bithiophene as a biolinker for surface plasmon resonance (SPR) spectroscopy are examined in this paper. By using an atomic force microscope (AFM), it was observed that the morphology of the bithiophene modified gold sensor surface became smoother than the original gold surface. We compared the response and concentration of the anti-IFN-γ antibody on a bithiophene-coated and dextran-coated biochip as well as on different thickness-modified surfaces under SPR relevant conditions. The results indicate that a response to IFN-γ molecules immobilized on a sensor using a bithiophene biolinker improved more than 8-fold when compared to that of a sensor using a dextran biolinker. Furthermore, the regeneration ability of the sensor surface shows good repeatability as only less than a 1% decrease was found after repeating the experimental work over 6 cycles. The characteristics provided us with a good platform for rapid screening, real-time monitoring and quantitative concentration of the autoimmune antibody activities.

Monitoring human serum albumin cell cultures using surface plasmon resonance (SPR) spectroscopy

Abstract. Continuously monitoring cell cultures is essential for both controlling critical parameters and improving understanding of key processes. An ideal technique in this context is surface plasmon resonance (SPR) spectroscopy, which essentially exploits changes in the angle of incident light that occur when molecules bind to a surface. It provides the ability to monitor real-time changes in small concentrations of various molecules, with no need for additional labels or sample preparation. Here we present an SPR-based immunoassay for monitoring concentrations of human serum albumin (HSA), and compare its sensitivity when used in conjunction with a Biacore platform and the cheaper, smaller liSPR system. In conjunction with either system, the immunoassay can detect HSA (a hepatocyte viability marker) at concentrations typically present in three-dimensional hepatocyte cultures mimicking the liver used to evaluate effects of drug candidates before exposure to humans or animals. Furthermore, in conjunction with the liSPR system, it is sufficiently sensitive to measure the much lower HSA levels present in skin–hepatocyte co-cultures.

In Situ Study of Electropolymerized Poly(3-aminobenzoic acid) Thin Film on BD-R and DVD-R Grating Substrates by Electrochemical-Transmission Surface Plasmon Resonance Spectroscopy

The electropolymerization process and doping/dedoping properties of poly(3-aminobenzoic acid) (PABA) thin films on gold-coated commercial BD-R and DVD-R grating substrates were simultaneously studied by the combination of electrochemical technique and transmission surface plasmon resonance (TSPR) spectroscopy. The optical property as a function of the applied potentials and time dependence during electropolymerization were studied. The obtained TSPR wavelength scan spectra after electropolymerization showed that the maximum wavelength slightly shifted to longer wavelength indicating the increase of film thickness. In addition, the change during construction of PABA-based immunosensor for label-free detection of human immunoglobulin G can be observed.

Linking Ag Nanoparticles by Aliphatic α,ω-Dithiols: A Study of the Aggregation and Formation of Interparticle Hot Spots

Linear α,ω-dithiols have been used as linkers to control the aggregation of silver nanoparticles. The characterization of the resulting nanoparticle clusters thus formed was carried out using plasmon resonance spectroscopy and transmission electron microscopy in both independent and correlated measurements. The obtained nanoparticle assemblies present morphologies that vary according to the dithiol length, displaying controllable-size interparticle gaps (plasmonic hot spots) with potential application in the detection of a large list of hydrophobic analytes.

Abstract 5563: Targeting the PH domain of TIAM1 to inhibit prostate cancer metastasis.

Abstract TIAM1 (T-lymphoma invasion and metastasis-inducing protein-1) is a highly conserved guanine nucleotide exchange factor and contains an Dbl Homology (DH)/C-terminal Pleckstrin Homology (PH) domain. The crystal structure of DH-PH of TIAM1 in complex with Rac-1 has been reported. TIAM1 has been found to be over-expressed cancers such as breast, colon and prostate cancers. An increase in TIAM1 expression has been shown to be associated with increased metastatic potential of breast cancer cell lines and is also correlated with poor prognosis of patients with prostate cancer. TIAM1 is thus a novel PH domain-containing drug target directly related to cancer progression, metastasis and patient survival. We have identified and characterized novel small molecule inhibitors targeting the phosphoinositide lipid binding PH domain of TIAM1 in order to selectively inhibit cell migration, invasion and survival. An In Silico screen of our internal and Maybridge library using the crystal structure of TIAM1 has identified 11 compounds that bind to the PH domain. In vitro assays revealed that compounds TPH-3 and TPH-15 significantly reduced the amount of active Rac1 in PC-3 prostate cancer cells (EC50 of 2.73±0.13 and 2.38±0.98 μM) by binding to PH-TIAM1 with high affinity (KD in the micromolar range) using surface plasmon resonance (SPR) spectrometry. Both compounds displaced PtdIns-3,4,5-P3 in a SPR competitive binding assay. TPH-3 and TPH-15 inhibited cell proliferation with EC50 of 19.8±3.2 and 28.7±1.7 μM in prostate cancer cells LnCaP and EC50 of 18.6±1.8 and 33.3±6.7 μM in PC-3. Wound healing assays and lamellipodia formation were both inhibited by the compounds. TPH-15 inhibited ≈70% of PC-3 invasion using a matrigel invasion assay. Finally, TPH-15 exhibits anti-tumor properties in a PC-3 mouse xenograft study (%T/C≈38.8) with good pharmacokinetic properties (T1/2≈5 hours). Cardio-injection of prostate PC-3 cells in SCID mice was used to test the effects of TPH-15 in the prevention of bone metastasis. Mice were treated with 50mg/kg ip of TPH-15 once a day for 5 days. TPH-15-treated mice developed significantly less pelvic bone lesions than the untreated group and TPH-15 treated mice lived longer, on average, than the untreated group. Overall, we have identified novel compounds which exhibit the ability to reduce prostate cancer bone metastasis by binding to the PH domain of TIAM1, an important GEF in the process of metastasis. Citation Format: Emmanuelle J. Meuillet, Sylvestor A. Moses, Jana Jandova, Eugene A. Mash, Shuxing Zhang. Targeting the PH domain of TIAM1 to inhibit prostate cancer metastasis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5563. doi:10.1158/1538-7445.AM2013-5563

Fabrication of Carboxylated Conducting Polymer/CNTs Composites Thin Films for Immunosensor Application

Electropolymerization of carboxylated conducting polymer/carbon nanotubes (CNTs) composites thin films has been studied by in situ electrochemical-surface plasmon resonance (EC-SPR) spectroscopy. Two derivatives of benzothiophene, thianaphthene-2-carboxylic acid and benzothiophene-2-propionic acid, composited with CNTs were electropolymerized in an acetonitrile with the potential range between 0 and 1.2 V at scan rate of 20 mV/s. The obtained films were characterized by in situ EC-SPR spectroscopy, UV-vis absorption spectroscopy, and atomic force microscopy. It was found that CNTs can improve properties of polymer/CNT composites films. Moreover, the obtained thianaphthene-2-carboxylic acid film can be further used for construction of immunosensor for detection of human IgG.

Multi-Functional Biomemory Device Composed of Recombinant Metalloprotein

We developed a multi-functional biomemory device composed of cytochrome c and recombinant azurins which have different metal ions in the core. Azurin, one of the well-known metalloproteins, was modified by attaching cysteine residue containing thiol functional group for direct immobilization without chemical linkers. The immobilization of metalloproteins was confirmed by atomic force microscopy (AFM) and surface plasmon resonance (SPR) spectroscopy. The redox properties of immobilized recombinant azurin were validated with cyclic voltammetry (CV), and memory functions using various metalloprotein structures were confirmed by the technique of open circuit potential amperometry (OCPA). We achieved various practical functions based on basic memory functions including write, erase, and read using recombinant azurin and other metalloproteins, and this proposed multifunctional biodevice could be directly applied to the realization of bioelectronics device for next generation, such as single molecular functional device, bioprocessor and biocomputing system.

Role of Defects in the Phase Transition of VO2 Nanoparticles Probed by Plasmon Resonance Spectroscopy

Defects are known to affect nanoscale phase transitions, but their specific role in the metal-to-insulator transition in VO(2) has remained elusive. By combining plasmon resonance nanospectroscopy with density functional calculations, we correlate decreased phase-transition energy with oxygen vacancies created by strain at grain boundaries. By measuring the degree of metallization in the lithographically defined VO(2) nanoparticles, we find that hysteresis width narrows with increasing size, thus illustrating the potential for domain boundary engineering in phase-changing nanostructures.

Lipid Vesicle-mediated Affinity Chromatography using Magnetic Activated Cell Sorting (LIMACS): a Novel Method to Analyze Protein-lipid Interaction

The analysis of lipid protein interaction is difficult because lipids are embedded in cell membranes and therefore, inaccessible to most purification procedures. As an alternative, lipids can be coated on flat surfaces as used for lipid ELISA and Plasmon resonance spectroscopy. However, surface coating lipids do not form microdomain structures, which may be important for the lipid binding properties. Further, these methods do not allow for the purification of larger amounts of proteins binding to their target lipids. To overcome these limitations of testing lipid protein interaction and to purify lipid binding proteins we developed a novel method termed lipid vesicle-mediated affinity chromatography using magnetic-activated cell sorting (LIMACS). In this method, lipid vesicles are prepared with the target lipid and phosphatidylserine as the anchor lipid for Annexin V MACS. Phosphatidylserine is a ubiquitous cell membrane phospholipid that shows high affinity to the protein Annexin V. Using magnetic beads conjugated to Annexin V the phosphatidylserine-containing lipid vesicles will bind to the magnetic beads. When the lipid vesicles are incubated with a cell lysate the protein binding to the target lipid will also be bound to the beads and can be co-purified using MACS. This method can also be used to test if recombinant proteins reconstitute a protein complex binding to the target lipid. We have used this method to show the interaction of atypical PKC (aPKC) with the sphingolipid ceramide and to co-purify prostate apoptosis response 4 (PAR-4), a protein binding to ceramide-associated aPKC. We have also used this method for the reconstitution of a ceramide-associated complex of recombinant aPKC with the cell polarity-related proteins Par6 and Cdc42. Since lipid vesicles can be prepared with a variety of sphingo- or phospholipids, LIMACS offers a versatile test for lipid-protein interaction in a lipid environment that resembles closely that of the cell membrane. Additional lipid protein complexes can be identified using proteomics analysis of lipid binding protein co-purified with the lipid vesicles.

Lipid Vesicle-mediated Affinity Chromatography using Magnetic Activated Cell Sorting (LIMACS): a Novel Method to Analyze Protein-lipid Interaction

The analysis of lipid protein interaction is difficult because lipids are embedded in cell membranes and therefore, inaccessible to most purification procedures. As an alternative, lipids can be coated on flat surfaces as used for lipid ELISA and Plasmon resonance spectroscopy. However, surface coating lipids do not form microdomain structures, which may be important for the lipid binding properties. Further, these methods do not allow for the purification of larger amounts of proteins binding to their target lipids. To overcome these limitations of testing lipid protein interaction and to purify lipid binding proteins we developed a novel method termed lipid vesicle-mediated affinity chromatography using magnetic-activated cell sorting (LIMACS). In this method, lipid vesicles are prepared with the target lipid and phosphatidylserine as the anchor lipid for Annexin V MACS. Phosphatidylserine is a ubiquitous cell membrane phospholipid that shows high affinity to the protein Annexin V. Using magnetic beads conjugated to Annexin V the phosphatidylserine-containing lipid vesicles will bind to the magnetic beads. When the lipid vesicles are incubated with a cell lysate the protein binding to the target lipid will also be bound to the beads and can be co-purified using MACS. This method can also be used to test if recombinant proteins reconstitute a protein complex binding to the target lipid. We have used this method to show the interaction of atypical PKC (aPKC) with the sphingolipid ceramide and to co-purify prostate apoptosis response 4 (PAR-4), a protein binding to ceramide-associated aPKC. We have also used this method for the reconstitution of a ceramide-associated complex of recombinant aPKC with the cell polarity-related proteins Par6 and Cdc42. Since lipid vesicles can be prepared with a variety of sphingo- or phospholipids, LIMACS offers a versatile test for lipid-protein interaction in a lipid environment that resembles closely that of the cell membrane. Additional lipid protein complexes can be identified using proteomics analysis of lipid binding protein co-purified with the lipid vesicles.

Abstract 2273: Validation of putative stem cell factor SOX2 as predictive marker in breast cancer – with overall poor prognosis

Abstract As member of the high-mobility-group (HMG)-domain containing proteins – SOX2 (Sex determining Region Y – box 2) transcriptional activator is known for its pivotal role in maintaining self-renewal, pluripotency and cellular identity in embryonic stem cells. While its status in adult tissue, e.g. in homeostasis – is still less understood and controversy – SOX2 has shown recently to be up regulated in a huge variety of human tumors like oesophagus, lung, brain and breast. Within this study whole sections – provided as formalin-fixed paraffin-embedded tumor samples, derived from 86 patients with advanced breast cancer disease were stained via immunohistochemistry (IHC) for SOX2 positivity. Further on – six breast cancer cell lines (MCF-7, MDA-MB231, MDA-MB453, SK-BR3, SUM-159, T47-D) as well as an individual based tissue micro array (TMA) containing 1080 fine needle biopsies were additionally analyzed using IHC and qRT-PCR. Initially – all samples have been evaluated for their particular molecular subtype (Luminal A, Luminal B, Normal-like, HER2 Overexpressing, Basal-like) and their histopathological parameters (histological subtype, grade, size, lymph node metastasis). For further proof of principle the applied SOX2 polyclonal antibody (SOX2 PAb AF2018, R&D SystemsTM) was validated for its marker capacity via Surface Plasmon Resonance (SPR) Spectroscopy and Western Blot to determine the kinetic profile, limit of detection, epitope variety and specificity of this antibody. With the so called ‘fishing’ opportunity for analyte recovery in SPR, native putative antigen bound by the SOX2 PAb can be enriched and further characterized from whole cell lysates. In conclusion – SOX2 showed association to overall bad prognosis due to high grade (p<0.001), huge size (p=0.003), lymph node metastasis (p<0.001) as well as histological and molecular subtypes with poor overall-survival (p<0.001). Further on it is independent (p=0.6) of oestrogen receptor (ER) presence but correlated to EGFR expression (p=0.007). During antibody-based validation – SOX2 PAb revealed to possess high specificity, sensitivity and affinity to native and recombinant SOX2 full length protein finally. In this way SOX2 – as marker, can be applied to predict overall poor prognosis in breast cancer in an ER- and subtype-independent fashion. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2273. doi:10.1158/1538-7445.AM2011-2273

A surface plasmon resonance study on the optical properties of gold nanoparticles on thin gold films

We report on an investigation of the optical properties of gold nanoparticles assembled as thin films of different thickness. The nanoparticles were linked to the surface of a gold chip by dithiol reagents and studied by surface plasmon resonance (SPR) spectroscopy and atomic force microscopy. There is good correlation between the experimental findings and theoretical simulation, and the respective data reveal the presence of ordered nanostructures in the assemblies. The shift in the SPR angle is linearly dependent on the particle size and the ratio of the different particles. SPR spectroscopy also reveals important information in terms of the optical constants of such films. This shall be further applied to in-situ quality control in the fabrication of optoelectronic, solar cell and semiconductor devices.