Standard Surface Plasmon Resonance Research Articles

Green Synthesis of Silver Nanoparticles Using Aqueous Fruit Peel Extract of Citrus aurantifolia: Optimization, Its Characterization and Stability Test

In this present study, silver nanoparticles were synthesized by green biological synthesis method using plant extract from fruit peel of Citrus aurantifolia as reducing agents. All the parameters in the synthesis of silver nanoparticles (AgNPs) were optimized to achieve a better yield, controlled size and stability of the particles. The biosynthesis of silver nanoparticles was monitored via UV-vis spectrophotometer and stability test was done. The resulting UV-Vis spectra of synthesized AgNPs from C. aurantifoliafruit peel extract (CAFPE) showed standard surface plasmon resonance band at 420 nm which indicated the presence of AgNPs. The optimum result was obtained with an optimum concentration at 4 mM AgNO3, leaving in a dark room temperature for 24 h and using a concentration 1:3 ratio (extract: silver nitrate). Moreover, the stability of the CAFPE-AgNPs was also observed after 30 days of synthesis and even up to 10 months, indicating optimization plays major role towards the stability fate of nanoparticles. The FTIR analysis showed possible functional groups of biomolecules that play roles in the bioreduction and capping of silver nanoparticles. In addition, it is believed that these parameters are highly suitable for bulk production of single spherical AgNPs with diameter 29.6- 45.2 nm confirmed via FESEM. Thus, the obtained results clearly suggest that optimization of silver nanoparticles may have important role in attaining a better yield and stability of metal nanoparticles, refraining back to its original structure or particles.

Fiber Optic Sensor of Ammonia Gas Using Plasmonic Extraordinary Optical Transmission.

While standard surface plasmon resonance (bio) sensing, relaying on propagating surface plasmon polariton sensitivity on homogeneous metal/dielectric boundaries, represents nowadays a routine sensing technique, other alternatives, such as inverse designs with nanostructured plasmonic periodic hole arrays, have been far less studied, especially in the context of gas sensing applications. Here, we present a specific application of such a plasmonic nanostructured array for ammonia gas sensing, based on a combination of fiber optics, extraordinary optical transmission (EOT) effect, and chemo-optical transducer selectively sensitive to ammonia gas. The nanostructured array of holes is drilled in a thin plasmonic gold layer by means of focused ion beam technique. The structure is covered by chemo-optical transducer layer showing selective spectral sensitivity towards gaseous ammonia. Metallic complex of 5-(4'-dialkylamino-phenylimino)-quinoline-8-one dye soaked in polydimethylsiloxane (PDMS) matrix is used in place of the transducer. Spectral transmission of the resulting structure and its changes under exposition to ammonia gas of various concentrations is then interrogated by fiber optics tools. The observed VIS-NIR EOT spectra are juxtaposed to the predictions performed by the rigorous Fourier modal method (FMM), providing useful theoretical feedback to the experimental data, and ammonia gas sensing mechanism of the whole EOT system and its parameters are discussed.

Adsorption independent silver colloids index measurement with metal-cladding optical waveguide

The refractive index measurements of silver nanoparticles colloids can provide chemical composition and nanostructure details. Although the standard surface plasmon resonance (SPR) approach improves index measurement precision, it is restricted by silver nanoparticles adsorption and incapable of detecting the colloid index due to the evanescent nature of the surface wave. Herein, a method utilizing metal-cladding optical waveguide (MCOW) was proposed to measure the volume refractive index of silver nanoparticles colloids, importantly, which is independent of particle adsorption. The experimental results show that the sensitivity of the refractive index measurement using the MCOW approach is at least 10−6 RIU (Refractive Index Unit) owing to the oscillating ultrahigh-order modes, this work not only presents a high-sensitivity, high-yield, simple-to-process, and effective refractive index measuring technique, but also recommends a more practical and adaptable colloidal particle characterization approach.

AC-Electroosmosis-Assisted Surface Plasmon Resonance Sensing for Enhancing Protein Signals with a Simple Kretschmann Configuration.

A surface plasmon resonance (SPR) sensor chip fabricated with a comb-shaped microelectrode array to supply alternating current (AC) voltage is reported. The chip induces circulating flow near the surface (i.e., AC electroosmosis). The circulating flow provides a mixing effect, which enhances the binding of the analyte molecules. We evaluated the SPR characteristics of the chip and demonstrated an improvement in protein binding to the chip surface. SPR sensor chips with comb-shaped microelectrodes were fabricated using standard UV lithography. Sensing experiments were conducted using a standard Kretschmann-type SPR measurement system. To demonstrate the mixing effect of AC electroosmosis, we evaluated the binding of immunoglobulin G molecules onto the sensor surface where anti-immunoglobulin G antibodies were covalently immobilized. The result indicates that the amount of binding increases by a factor of 1.7 above that achieved by using a conventional chip, suggesting enhancement of the protein signal.

Real Time SPR Assessment of the Structural Changes of Adaptive Dynamic Constitutional Frameworks as a New Route for Sensing.

Cross linked gold-dynamic constitutional frameworks (DCFs) are functional materials of potential relevance for biosensing applications, given their adaptivity and high responsivity against various external stimuli (such as pH, temperature) or specific interactions with biomolecules (enzymes or DNA) via internal constitutional dynamics. However, characterization and assessment of their dynamic conformational changes in response to external stimuli has never been reported. This study proves the capability of Surface Plasmon Resonance (SPR) assays to analyse the adaptive structural modulation of a functional matrix encompassing 3D gold-dynamic constitutional frameworks (Au-DCFs) when exposed to pH variations, as external stimuli. We analyse Au-DCFs formed from Au nanoparticles, (AuNP) connected through constitutionally dynamic polymers, dynamers, with multiple functionalities. For increased generality of this proof-of-concept assay, Au-DCFs, involving DCFs designed from 1,3,5-benzene-tricarbaldehyde (BTA) connecting centres and polyethylene glycol (PEG) connectors, are covalently attached to standard SPR sensing chips (Au nanolayers, carboxyl terminated or with carboxymethyl dextran, CMD top-layer) and analysed using state-of-the art SPR instrumentation. The SPR effects of the distance from the Au-DCFs matrix to the Au nanolayer of the sensing chip, as well as of Au-DCFs thickness were investigated. This study reveals the SPR response, augmented by the AuNP, to the conformational change, i.e., shrinkage, of the dynamer and AuNP matrix when decreasing the pH, and provides an unexplored insight into the sensing applicability of SPR real-time analysis of adaptive functional materials.

Sensitivity enhancement of surface plasmon resonance sensor using 2D material barium titanate and black phosphorus over the bimetallic layer of Au, Ag, and Cu

A unique surface plasmon resonance (SPR) biosensors is proposed computationally in this paper, combining recently developed Perovskite (e.g., BaTiO 3) with 2D materials (e.g., black phosphorus) atop of standard SPR biosensors. The performance of the proposed structure, such as sensitivity, the figure of merit (FOM), and the quality factor (QF) of the sensors, are evaluated using the attenuated total reflection (ATR) approach. The Ag/BaTiO 3/BP, Au/BaTiO 3/BP and Cu/BaTiO 3/BP structures, respectively, have exceptionally high sensitivity of 360°/RIU, 299°/RIU, and 378°/RIU, which are 1.5, 0.55, and 1.86 times greater than the conventional silver (Ag), gold (Au), copper (Cu) based sensors, with equivalent FOM and QF. For the bimetallic layer first metal Ag, Au, and Cu-based sensors, the thickness of Ag/Au/Cu is 50/40/35nm, and the thickness of the second metal layer is 10 nm, and the number of BP layers is 0.34 for Ag/Au/Cu-based sensors. BaTiO 3 is employed in all cases with an optimum thickness of 5 nm. The proposed biosensors’ remarkable performance will pave the road for their implementation in future medical diagnostics and biological detection applications.

A Kretschmann setup at acoustic frequencies for studying molecular vibration

In this study, simultaneous measurement of surface plasmon resonance (SPR) and surface enhanced Raman scattering (SERS) on flat metallic surfaces was demonstrated in a setup based on the Kretschmann configuration at acoustic frequency. This asset facilitates matching the photon and the surface plasmon polaritons wavevectors by tunneling the photon in the total internal reflection geometry and we demonstrate the compensation for the absence of hotspots typical on rough surfaces. The optomechanical asset allows detecting the two signals and prevents their interference. Experimental and numerical analyses were done for characterizing the two signals. The results emphasize the enhancement of the electromagnetic field at the surface, which provides high sensitivity for detecting the signals coming from the Raman probe molecules such as Congo red and thiols such as cysteamine. The combination of simultaneous SPR–SERS microspectroscopy at low frequencies opens up interesting prospects that facilitate experimental conditions using standard SPR setups, with a dramatic reduction in sensor cost.

Improved Detection of Plasmon Waveguide Resonance Using Diverging Beam, Liquid Crystal Retarder, and Application to Lipid Orientation Determination.

Plasmon waveguide resonance (PWR) sensors exhibit narrow resonances at the two orthogonal polarizations, transverse electric (TE) and transverse magnetic (TM), which are narrower by almost an order of a magnitude than the standard surface plasmon resonance (SPR), and thus the figure of merit is enhanced. This fact is useful for measuring optical anisotropy of materials on the surface and determining the orientation of molecules with high resolution. Using the diverging beam approach and a liquid crystal retarder, we present experimental results by simultaneous detection of TE and TM polarized resonances as well as using fast higher contrast serial detection with a variable liquid crystal retarder. While simultaneous detection makes the system simpler, a serial one has the advantage of obtaining a larger contrast of the resonances and thus an improved signal-to-noise ratio. Although the sensitivity of the PWR resonances is smaller than the standard SPR, the angular width is much smaller, and thus the figure of merit is improved. When the measurement methodology has a high enough angular resolution, as is the one presented here, the PWR becomes advantageous over other SPR modes. The possibility of carrying out exact numerical simulations for anisotropic molecules using the 4 × 4 matrix approach brings another advantage of the PWR over SPR on the possibility of extracting the orientation of molecules adsorbed to the surface. High sensitivity of the TE and TM signals to the anisotropic molecules orientation is found here, and comparison to the experimental data allowed detection of the orientation of lipids on the sensor surface. The molecular orientations cannot be fully determined from the TM polarization alone as in standard SPR, which underlines the additional advantage of the PWR technique.

Correlation of antibacterial and time resolved photoluminescence studies using bio-reduced silver nanoparticles conjugated with fluorescent quantum dots as a biomarker

This report lays the foundation stone for the real time detector to control and monitor antibiotic resistant bacteria’s. To start with, firstly, the green synthesis of silver nanoparticles were done by the bio-reduction of silver nitrate using different concentrations of medicinal plant extract taken from the leaves of Azadirachta indica (neem). The well-known standard surface plasmon resonance (SPR) wavelength of 430 nm and the characteristic brown color of the solution confirms the formation of eco-friendly silver nanoparticles. The silver nanoparticle size in the range of 10–20 nm was observed from TEM measurements for the sample showing best SPR which was further selected for conjugation with QDs. Secondly glutathione capped ZnS:Mn QDs were synthesized and conjugated with silver nanoparticles (0.09–0.1 mg/mL) and then their zone of inhibition studies were done using antibiotic resistant gram positive as well as gram negative bacteria’s i.e. Staphylococcus aureus and Escherichia coli respectively. Lastly, time resolved photoluminescence studies of the conjugated system were done to correlate zone of inhibition (antibiotic sensitivity) with silver nanoparticle concentration in both the cases of a gram positive bacteria and gram negative bacteria. Luminescence intensity of glutathione capped QDs conjugated silver nanoparticles decreases with increasing concentration of silver nanoparticles in tune with the increasing zone of inhibition (antibiotic sensitivity). This is very important for making a fluorescence based detector to monitor antibiotic resistant bacteria’s.

Multiplex blood group typing by cellular surface plasmon resonance imaging.

Blood-group typing of donors and patients is essential to avoid incompatible transfusions. Transfusion of incompatible RBCs may result in alloimmunization complicating future transfusions or in the presence of antibodies in adverse reactions. With more than 300 blood group antigens identified, it is difficult to provide fully compatible blood. Currently, standard practice is to match for the most immunogenic antigens. While the current agglutination-based RBC-typing methods are reliable for testing a selected number of antigens, they are not easily adaptable for high-throughput multiplex blood typing beyond the current standard. Surface plasmon resonance (SPR) is a label-free method to follow molecular-and, very recently, also cellular-interactions in real time. Demonstration of binding of RBCs to blood group antigen-specific antibodies by SPR has already been achieved. Here, we demonstrate the generation of an SPR array equipped with clinically relevant blood group antibodies (A, B, and Rh blood groups). To validate this method, we blindly compared typing of 946 blood donors with results of current diagnostic agglutination-based methods. RBC typing was achieved by monitoring RBC binding to blood group-specific antibodies on the sensor simultaneously within 5 minutes per sample. Regeneration of the chip was robust, allowing for typing of at least 100 samples. The typing results gave a 100% match with classical serology with all antibodies tested besides anti-E/e monoclonals, which gave inconsistent results due to low antibody specificity. This study demonstrates that SPR-based RBC typing for multiple antigens can be realized simultaneously with high-quality antibodies, enabling reduced hands-on time and possibly improving cost efficiency.

Expression of Recombinant β2GPI and Site-Directed Mutants Provides Insight into the Pathogenesis of Antiphospholipid Syndrome

Introduction:Antiphospholipid syndrome (APS) is an autoimmune disorder caused by “antiphospholipid” antibodies (aPL) directed against β2-glycoprotein I (β2GPI). In the presence of β2GPI, aPL activate endothelial cells through TLR4-mediated and other pathways. Previous studies suggest that a region encompassing amino acids 39-43 of β2GPI domain 1 comprises an important binding site for pathogenic aPL. However, due to difficulty in expressing full-length recombinant β2GPI, antibody specificity has only been tested using individual, recombinant β2GPI domains. Further definition of antibody specificity using intact recombinant β2GPI provides a new approach for diagnostic and mechanistic studies. In the present study we describe the expression of full-length, wild-type recombinant β2GPI and site-directed mutants encompassing the putative β2GPI binding region in domain 1. Binding of APS patient-derived anti-β2GPI antibodies to these proteins and their ability to support anti-β2GPI-mediated endothelial cell activation was determined.Methods:Full length APOH cDNA with a modified signal peptide (spm) was cloned into the lentiviral vector pLenti CMV Puro DEST. We generated two mutants spanning the 39 to 43 amino acid region: SEGVG (R39S; G40E; M42V; R43G) and AAGMA (R39A; G40A; R43A). The final recombinant plasmids were termed as pDEST-spmAPOH-WT; pDEST-spmAPOH-SEGVG and pDEST-spmAPOH-AAGMA. Lentivirus was produced using the Lentiviral Gateway Expression kit using GP2-293 (HEK) cells. Stable cell lines were generated by transducing HEK cells with APOH-lentivirus and selecting against puromycin. Stable cell lines were transferred to serum-free media and grown in suspension. Cell culture supernatants containing secreted β2GPI were filtered and concentrated, and recombinant β2GPI was purified using a hitrap-heparin column.Anti-β2GPI antibody binding to plasma-derived and rβ2GPI was determined using a standard β2GPI ELISA and SPR (Surface Plasmon Resonance) on a Biacore 3000. Biosensor analysis was performed by crosslinking β2GPI to carboxymethyl-dextran coated sensor chips using amine coupling. Anti-β2GPI antibodies at concentrations ranging from 1-15,000 nM, were flowed through channels until equilibrium binding was achieved, at which point dissociation was assessed over a 10 minute interval. The BIAevaluation program was used to calculate association and dissociation rates. Endothelial cell activation was assessed by measuring cell surface E-selectin expression after incubating cells with control IgG or anti-β2GPI antibodies in the presence or absence of wild-type or mutant rβ2GPI. Molecular modeling was performed using PyMol.Results:After transduction with lentivirus encoding β2GPI with a modified signal peptide, HEK-293 cells were able to express and efficiently secrete rβ2GPI and site-directed mutants. Using a standard β2GPI-ELISA and SPR we found no significant differences in binding affinity of aPL towards plasma-derived and wild-type rβ2GPI. However, in the anti-β2GPI ELISA, binding of patient-derived aPL (APS21) to both mutants was reduced by ~70% compared to wild-type rβ2GPI. Consistent with binding specificity for a region encompassing aa 39-43, the Kd for binding of APS21 anti-β2GPI antibodies to wild-type and rβ2GPI-SEGVG determined by SPR was 20 nM and 5000 nM, respectively. Moreover, the ability of patient-derived APS21 anti-β2GPI antibodies to activate endothelial cells was reduced by >60% in the presence of rβ2GPI-SEGVG compared to wild-type rβ2GPI. Molecular modeling of β2GPI demonstrated that a mutation in the aa 39-43 region is predicted to cause a change from a net positive to a net negative charge without any structural change (Figure 1).Conclusion:These studies are the first to assess binding of human anti-β2GPI antibodies to rβ2GPI and site-directed mutants expressed in mammalian cells. No significant differences between binding of aPL to plasma derived and wild-type rβ2GPI were observed. APS21 aPL has specificity towards epitope 39-43 of β2GPI domain 1 and its binding affinity to rβ2GPI-SEGVG was significantly reduced. Functional studies demonstrate the importance of β2GPI aa 39 to 43 in supporting endothelial cell activation by anti-β2GPI antibodies. These recombinant proteins should facilitate further studies concerning the role of aPL-β2GPI interactions in the diagnosis and pathogenesis of APS. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Surface-plasmon optical-heterodyne clock biosensor

Surface-plasmon resonance (SPR) sensors represent a formidable technology for molecular biology and bioanalytics applications. Here, we devise a new interrogation architecture that transforms a standard SPR chip into an optical-heterodyne clock detector comparable with the best SPR instruments. The key ingredients are (i) the conversion of refractive-index changes on the SPR chip into frequency shifts of an oscillatory electronic signal (ii) a differential probe & reference optical-cavity scheme that cancels out most source/detector noise contributions. A rigorous characterization of the sensor performance with the integration time demonstrates a refractive-index resolution on the 10−8-RIU level over a 1-s timescale using a bare, unstabilized SPR element. A bio-sensing test with a functionalized surface interfaced with a microfluidic flow-cell is carried out, showing detection of streptavidin via covalent bond down to concentrations of 90 fg/mm2.

Detection of tuberculosis in patients with the use of portable SPR device

Tuberculosis (TB) is still one of the important causes of death worldwide. Its detection is challenging and new tools for TB diagnostics are highly needed. In this work, we investigated a possibility of using surface plasmon resonance (SPR) phenomenon in detection of TB bacteria in sputum. For this purpose we designed a portable SPR apparatus. We compared its performance with a standard desktop SPR platform designed to work in laboratory by measuring response to Ag85 – TB secretory protein. We examined samples of suspended Mycobacterium tuberculosis cultures and sputum samples of TB patients. The device was able to detect M. tuberculosis secretory protein (Ag85) in concentration of 10 ng/ml which was comparable to the desktop SPR equipment. It has been also able to detect TB bacteria cultures in concentration of 1*104 cfu/ml with no significant interfering response from two other bacteria species. Finally, detection of bacteria in sputum of confirmed tuberculosis patients has been demonstrated.

Sensitivity enhancement of a surface plasmon resonance sensor using porous metamaterial layers

In this work, the surface plasmon resonance (SPR) device with two porous left handed metamaterial (LHM) layers separated by an insulator gap, is investigated. The effect of the insulator gap thickness and its refractive index (RI) on the angular response of the device is analyzed. The results show that the sensitivity of the SPR sensor is enhanced compared to the standard SPR sensors. Here, the multilayer structure is probed with 738 nm-wavelength, and electromagnetic properties of active porous LHM layers are described from the effective medium theory (EMT). Furthermore, in the increase of the porosity from 0 to 0.6, the designed nanocavity exhibits a fundamental SPR mode long-range (LR) type and it can be of interest in high-performance SPR sensing.

Surface Plasmon Sensor Based on a Dual Dielectric–Silver Photonic Crystal

We present a new type of biosensor. The principle of operation of the device is similar to conventional surface plasmon sensors, except that the ordinary metallic film in surface plasmon sensors is replaced by a one-dimensional photonic bandgap array. The advantages of using a photonic bandgap structure, instead of a metallic film, include enhanced sensitivity, physical and chemical robustness, and the ability to engineer the optical response of the device. We propose and elaborate a biosensor based on a onedimensional (1D) photonic crystal (PC) with a surface plasmon resonance (SPR). In comparison with standard SPR sensors that use silver (Ag ) or gold (Au) films, PC–Ag–PC–Au structures have narrower resonance widths, lower minimum reflectance, and higher sensitivity, making them a much better choice for biosensing applications. Moreover, the structure is compact (H = 1.139 μm), providing a better option in biosensing in comparison with other PC-SPR and conventional SPR sensors.

Plasmonic Perfect Absorbers for Biosensing Applications

We present a theoretical modal investigation of plasmonic perfect absorbers (PPAs) based on the localized surface plasmon resonance (LSPR) for biosensing applications. We design the PPA geometry with a layer of periodic metallic nanoparticles on one side of a dielectric substrate and a single metallic layer on the opposite side. The electromagnetic (EM) fields confine partly in the surrounding medium above the substrate and within the substrate itself. We examine the modes of the PPA geometry for a wavelength range of 600–1500 nm. The fundamental mode of the system provides perfect absorption for a wide angle of incidence 0–70°. The second-order mode shows a strong angular dependence with a sharp resonance and exhibits perfect optical absorption when the critical coupling condition for LSPR is achieved. The coupling condition depends on the size, periodicity, dielectric spacer, and the surrounding material of the system. The strong dependence on the surrounding material makes it a promising candidate for biosensing applications. We introduce a novel approach to investigate the angular dependence of the refractive index change for the PPA system. This novel technique contributes the significant attributes of the LSPR sensors, can be used for any required resonance wavelength depending on geometric design, and it also provides sensitivity analogous to the standard surface plasmon resonance (SPR) biosensors.

Investigation of DNA sequence recognition by a streptomycete MarR family transcriptional regulator through surface plasmon resonance and X-ray crystallography

Consistent with their complex lifestyles and rich secondary metabolite profiles, the genomes of streptomycetes encode a plethora of transcription factors, the vast majority of which are uncharacterized. Herein, we use Surface Plasmon Resonance (SPR) to identify and delineate putative operator sites for SCO3205, a MarR family transcriptional regulator from Streptomyces coelicolor that is well represented in sequenced actinomycete genomes. In particular, we use a novel SPR footprinting approach that exploits indirect ligand capture to vastly extend the lifetime of a standard streptavidin SPR chip. We define two operator sites upstream of sco3205 and a pseudopalindromic consensus sequence derived from these enables further potential operator sites to be identified in the S. coelicolor genome. We evaluate each of these through SPR and test the importance of the conserved bases within the consensus sequence. Informed by these results, we determine the crystal structure of a SCO3205-DNA complex at 2.8 Å resolution, enabling molecular level rationalization of the SPR data. Taken together, our observations support a DNA recognition mechanism involving both direct and indirect sequence readout.

Hydrogenated amorphous silicon nitride photonic crystals for improved-performance surface electromagnetic wave biosensors

We exploit the properties of surface electromagnetic waves propagating at the surface of finite one dimensional photonic crystals to improve the performance of optical biosensors with respect to the standard surface plasmon resonance approach. We demonstrate that the hydrogenated amorphous silicon nitride technology is a versatile platform for fabricating one dimensional photonic crystals with any desirable design and operating in a wide wavelength range, from the visible to the near infrared. We prepared sensors based on photonic crystals sustaining either guided modes or surface electromagnetic waves, also known as Bloch surface waves. We carried out for the first time a direct experimental comparison of their sensitivity and figure of merit with surface plasmon polaritons on metal layers, by making use of a commercial surface plasmon resonance instrument that was slightly adapted for the experiments. Our measurements demonstrate that the Bloch surface waves on silicon nitride photonic crystals outperform surface plasmon polaritons by a factor 1.3 in terms of figure of merit.

Self‐Assembled Arrays of Dendrimer–Gold‐Nanoparticle Hybrids for Functional Cell Studies

Engineered surfaces with nanoscale features of gold on silicon or glass have recently been used to improve the understanding of adhesion-mediated environmental sensing of cells. Often such surfaces present a cell-binding ligand, such as arginine–glycine–aspartic acid (RGD) peptide motifs, at controlled intramolecular distances on an inert background surface such as polyethylene glycol (PEG). The adhesion mechanism of macromolecular ligands in which direct interaction with cells is nonspecific is not known and the cell response is dictated by the type and the concentration of proteins adsorbed from solution. Dendrimers may increase the availability and multivalency of cell-interacting ligands as a consequence of their branched shape and inherently high concentration of end groups. It is therefore interesting to examine the eventual effect of the macromolecular architecture on the cell viability by the controlled reduction of ligands on a surface. Herein, we demonstrate the fabrication of selfassembledmacromolecular hybrid arrays in which the relative position of two anionic macromolecules of different architectures—a carboxy-functionalized dendrimer and a linear polymer—is straightforwardly controlled on a PEG surface. We also show how the interaction of primary human endothelial cells with these surfaces is modulated by the molecular spacing and how protein binding to the macromolecular arrays can be evaluated by using a standard surface plasmon resonance (SPR) technique. Self-assembled, short-range-ordered Au nanoparticle (NP) arrays were used as a versatile template to arrange polymeric entities at the nanometer scale (Figure 1a). This

Enhanced gas sensing performance of TiO2 functionalized magneto-optical SPR sensors

Porous TiO2 thin films deposited by glancing angle deposition are used as sensing layers to monitor their sensing capabilities towards Volatile Organic Compounds both in a standard Surface Plasmon Resonance (SPR) sensor and in Magneto-Optical Surface Plasmon Resonance (MO-SPR) configuration in order to compare their sensing performances. Here our results on the enhanced sensing capability of these TiO2 functionalized MO-SPR sensors with Au/Co/Au transducers with respect to traditional SPR gas sensors are presented.