Classical Surface Plasmon Resonance Research Articles

Phthalocyanine and Porphyrin Derivatives and Their Hybrid Materials in Optical Sensors Based on the Phenomenon of Surface Plasmon Resonance

In this review, the state of research over the past fifteen years in the field of the applications of metal phthalocyanines and porphyrin derivatives as well as their hybrid materials with carbon nanotubes, metal oxides, and polymers in optical sensors based on the phenomenon of surface plasmon resonance (SPR) is analyzed. The first chapter of the review presents an analysis of works on the use of porphyrins and phthalocyanines in classical SPR sensors for the detection of gases and volatile organic vapors, as well as their improved modifications, such as total internal reflection ellipsometry (TIRE) and magneto-optical SPR (MOSPR) methods, while the second chapter is devoted to their application for the detection of various analytes in solutions. The third chapter of the review summarizes publications describing recent advances in the use of porous materials based on hybrids of carbon nanotubes and oxides with metal phthalocyanines. The fourth chapter describes two-dimensional metal-organic frameworks (MOFs) based on metal porphyrin derivatives as SPR sensitizers.

Label-Free Multiplexed Microfluidic Analysis of Protein Interactions Based on Photonic Crystal Surface Mode Imaging.

High-throughput protein assays are crucial for modern diagnostics, drug discovery, proteomics, and other fields of biology and medicine. It allows simultaneous detection of hundreds of analytes and miniaturization of both fabrication and analytical procedures. Photonic crystal surface mode (PC SM) imaging is an effective alternative to surface plasmon resonance (SPR) imaging used in conventional gold-coated, label-free biosensors. PC SM imaging is advantageous as a quick, label-free, and reproducible technique for multiplexed analysis of biomolecular interactions. PC SM sensors are characterized by a longer signal propagation at the cost of a lower spatial resolution, which makes them more sensitive than classical SPR imaging sensors. We describe an approach for designing label-free protein biosensing assays employing PC SM imaging in the microfluidic mode. Label-free, real-time detection of PC SM imaging biosensors using two-dimensional imaging of binding events has been designed to study arrays of model proteins (antibodies, immunoglobulin G-binding proteins, serum proteins, and DNA repair proteins) at 96 points prepared by automated spotting. The data prove feasibility of simultaneous PC SM imaging of multiple protein interactions. The results pave the way to further develop PC SM imaging as an advanced label-free microfluidic assay for the multiplexed detection of protein interactions.

Can classical surface plasmon resonance advance via the coupling to other analytical approaches?

For nearly 40 years, surface plasmon resonance (SPR) analysis has been used to better understand the binding interaction strength between surface immobilized bioreceptors and the analytes of interest. The advantage of surface plasmon resonance, over other affinity sensing approaches such as Western blots and ELISAs approaches, resides in its possibility to reveal binding kinetics in a label-free manner. The concept of surface plasmon resonance has in addition been widely employed for the development of biosensors capitalizing on its direct assay format, short response times, simple sample treatments along with multiplexed sensing possibilities. To this must be added the possibility to reach high sensitivity due to the capability of surface plasmon resonance to detect very small changes in refractive index at the sensing interfaces in particular for analytes of larger size such as cells (e.g., bacteria), proteins, peptides and oligonucleotides. Challenges inherent to all affinity approaches call for further research and include non-specific surface binding events, mass transportation restrictions, steric hindrance, and the risk of data misinterpretation in case of lack of selective analyte binding. This opinion article is devoted to outlining the different approaches proposed to address these challenges by e.g., coupling with fluorescence read out, electrochemical sensing, mass spectroscopy analysis and more recently to integrate lateral flow concepts into surface plasmon resonance. Other plasmonic methods such as localized surface plasmon resonance (LSPR), surface enhanced Raman spectroscopy (SERS) will not be considered in detail, as such techniques have nowadays their own standing.

Nonlinear interferometric surface-plasmon-resonance sensor.

A nonlinear interferometer can be constructed by replacing the beam splitter in the Mach-Zehnder interferometer with four-wave mixing (FWM) process. Meanwhile, the conventional surface plasmon resonance (SPR) sensors can be extensively used to infer the information of refractive index of the sample to be measured via either angle demodulation technique or intensity demodulation technique. Combined with a single FWM process, a quantum SPR sensor has been realized, whose noise floor is reduced below standard quantum limit with sensitivity unobtainable with classical SPR sensor. Therefore, in this work we have theoretically proposed a nonlinear interferometric SPR sensor, in which a conventional SPR sensor is placed inside nonlinear interferometer, which is called as I-type nonlinear interferometric SPR sensor. We demonstrate that near resonance angle I-type nonlinear interferometric SPR sensor has the following advantages: its degree of intensity-difference squeezing, estimation precision ratio, and signal-noise-ratio are improved by the factors of 4.6 dB, 2.3 dB, and 4.6 dB respectively than that obtained with a quantum SPR sensor based on a single FWM process. In addition, the theoretical principle of this work can also be expanded to other types of sensing, such as bending, pressure, and temperature sensors based on a nonlinear interferometer.

Dielectric-Loaded Waveguides as Advanced Platforms for Diagnostics and Application of Transparent Thin Films

An alternative approach to classical surface plasmon resonance spectroscopy is dielectric-loaded waveguide (DLWG) spectroscopy, widely used in the past decades to investigate bio-interaction kinetics. Despite their wide application, a successful and clear approach to use the DLWGs for the one-step simultaneous determination of both the thickness and refractive index of organic thin films is absent in the literature. We propose here, for the first time, an experimental protocol based on the multimodal nature of DLWGs to be followed in order to evaluate the optical constants and thickness of transparent thin films with a unique measurement. The proposed method is general and can be applied to every class of transparent organic materials, with a resolution and accuracy which depend on the nature of the external medium (gaseous or liquid), the geometrical characteristics of the DLWG, and the values of both the thickness and dielectric constant of the thin film. From the experimental point of view, the method is demonstrated in a nitrogen environment with an accuracy of about 3%, for the special case of electroluminescent thin films of Eu3+β-diketonate complexes, with an average thickness of about 20 nm. The high value of the refractive index measured for the thin film with the Eu(btfa)3(t-bpete) complex was confirmed by the use of a spectroscopic model based on the Judd-Ofelt theory, in which the magnetic dipole transition 5D0 → 7F1 (Eu3+) for similar films containing Eu3+ complexes is taken as a reference. The DLWGs are finally applied to control the refractive index changes of the organic thin films under UVA irradiation, with potential applications in dosimetry and monitoring light-induced transformation in organic thin films.

Amplitude- and Phase-Resolved Infrared Nanoimaging and Nanospectroscopy of Polaritons in a Liquid Environment.

Polaritons allow for strong light-matter coupling and for highly sensitive analysis of (bio)chemical substances and processes. Nanoimaging of the polaritons' evanescent fields is critically important for experimental mode identification and field confinement studies. Here we describe two setups for polariton nanoimaging and spectroscopy in liquid. We first demonstrate the mapping of localized plasmon polaritons in metal antennas with a transflection infrared scattering-type scanning near-field optical microscope (s-SNOM), where the tip acts as a near-field scattering probe. We then demonstrate a total internal reflection (TIR)-based setup, where the tip is both launching and probing ultraconfined polaritons in van der Waals materials (here phonon polaritons in hexagonal boron nitride flakes), laying the foundation for s-SNOM-based polariton interferometry in liquid. Our results promise manifold applications, for example, in situ studies of strong coupling between polaritons and molecular vibrations or chemical reactions at the bare or functionalized surfaces of polaritonic materials.

Performance improvement of plasmonic sensors using a combination of AC electrokinetic effects for (bio)target capture.

Analytes concentration techniques are being developed with the appealing expectation to boost the performance of biosensors. One promising method lies in the use of electrokinetic forces. We present hereafter a new design for a microstructured plasmonic sensor which is obtained by conventional microfabrication techniques, and which can easily be adapted on a classical surface plasmon resonance imaging (SPRI) system without further significant modification. Dielectrophoretic trapping and electro-osmotic displacement of the targets in the scanned fluid are performed through interdigitated 200μm wide gold electrodes that also act as the SPR-sensing substrate. We demonstrate the efficiency of our device's collection capabilities for objects of different sizes (200nm and 1μm PS beads, as well as 5-10μm yeast cells). SPRI is relevant for the spatial analysis of the mass accumulation at the electrode surface. We demonstrate that our device overcomes the diffusion limit encountered in classical SPR sensors thanks to rapid collection capabilities (<1 min) and we show a consequent improvement of the detection limit, by a factor >300. This study of an original device combining SPRI and electrokinetic forces paves the way to the development of fully integrated active plasmonic sensors with direct applications in life sciences, electrochemistry, environmental monitoring and agri-food industry.

Optimal conditions for SPR-imaging of nano-objects

Approaches commonly used for the description of surface plasmon resonance (SPR) presume infinite transverse dimensions of interacting layers. Obviously, the interaction of nano-sized objects with plasmon-generating surfaces contradicts this assumption. In the present work, a simple model accounting for the finite dimension of nano-objects is applied, explaining experimentally observed effects of SPR detection of such objects. The model considers the radiation of a plasmon appearing in the gold layer around a particle as a main factor of image formation. This secondary plasmon appears due to scattering of the primary plasmons excited in the gold layer near the SPR resonance. The new approach allows for the optimization of the angle of incidence as well as the sensor layer parameters, providing a more than 10-fold improvement of the sensitivity compared to using the parameters usually applied in classical SPR.

Functional assessment of antibody oxidation by native mass spectrometry

Oxidation of methionine (Met) residues is one of several chemical degradation pathways for recombinant IgG1 antibodies. Studies using several methodologies have indicated that Met oxidation in the constant IgG1 domains affects in vitro interaction with human neonatal Fc (huFcRn) receptor, which is important for antibody half-life. Here, a completely new approach to investigating the effect of oxidative stress conditions has been applied. Quantitative ultra-performance liquid chromatography mass spectrometry (MS) peptide mapping, classical surface plasmon resonance and the recently developed FcRn column chromatography were combined with the new fast-growing approach of native MS as a near native state protein complex analysis in solution. Optimized mass spectrometric voltage and pressure conditions were applied to stabilize antibody/huFcRn receptor complexes in the gas phase for subsequent native MS experiments with oxidized IgG1 material. This approach demonstrated a linear correlation between quantitative native MS and IgG-FcRn functional analysis.In our study, oxidation of the heavy chain Met-265 resulted in a stepwise reduction of mAb3/huFcRn receptor complex formation. Remarkably, a quantitative effect of the heavy chain Met-265 oxidation on relative binding capacity was only detected for doubly oxidized IgG1, whereas IgG1 with only one oxidized heavy chain Met-265 was not found to significantly affect IgG1 binding to huFcRn. Thus, mono-oxidized IgG1 heavy chain Met-265 most likely does not represent a critical quality attribute for pharmacokinetics.

Investigation of surface plasmon resonance phenomena by finite element analysis and Fresnel calculation

In this study, a novel simulated method was developed to provide a graphical and simplistic simulation technique for the purpose of enhancing feasibility of classical surface plasmon resonance (SPR) experiment. Winspall, the software based on the Fresnel equations and the matrix formalism was used to compute the reflectivity of optical multilayer systems. In a simulation study, SPR curves were plotted using Winspall with ultrapure water, 50% ethanol aqueous solvent and pure ethanol as the environmental media. SPR angles of 67.1°, 71.7° and 72.5° were obtained, respectively. These values displayed significant disparity from the experimental data of 62.7°, 65.1° and 65.3° under the same conditions. Finite element analysis (FEA) was then evaluated for its suitability as a better alternative method. By establishing a new Kretchmann SPR model and simulating the S11 parameters, the obtained SPR angles of 62.6°, 65.0° and 65.3° agreed well with the experimental results. Thus FEA method was a more feasible alternative based on our experimental conditions. Hence, an optimal methodology for the theoretical study of SPR detection was developed in this study which contains port boundary conditions, background filed and period boundary conditions. More importantly, this study has established a new avenue of SPR chip applications for portable SPR devices.

Metallic Nanowire Array–Polymer Hybrid Film for Surface Plasmon Resonance Sensitivity Enhancement and Spectral Range Enlargement

In this paper, the coupling interaction is investigated between a metallic nanowire array and a metal film under the Kretschmann condition. The plasmonic multilayer is composed of a metallic nanowire array embedded in a polymer layer positioned above a metal film, exploiting the classical surface plasmon resonance (SPR) configuration. We analyze the influence of various structural parameters of the metallic nanowire array on the SPR spectrum of thin metal film. The results show that the coupling interactions of nanowires with the metal film can greatly affect SPR resonance wavelength and increase SPR sensitivity. The coupling strength of metallic nanowire array and metal film also impacts resonance wavelength, which can be used to adjust SPR range but have little effect on its sensitivity. The results are confirmed using a dipole coupling resonance model of metallic nanowire. We demonstrated that this nanostructured hybrid structure can be used for high sensitivity SPR monitoring in a large spectral range, which is important for advanced SPR measurement including fiber-optic SPR sensing technology.

Simulated single-cycle kinetics improves the design of surface plasmon resonance assays

Instruments based on the surface plasmon resonance (SPR) principle are widely used to monitor in real time molecular interactions between a partner, immobilized on a sensor chip surface and another one injected in a continuous flow of buffer. In a classical SPR experiment, several cycles of binding and regeneration of the surface are performed in order to determine the rate and the equilibrium constants of the reaction. In 2006, Karlsson and co-workers introduced a new method named single-cycle kinetics (SCK) to perform SPR assays. The method consists in injecting sequentially increasing concentrations of the partner in solution, with only one regeneration step performed at the end of the complete binding cycle. A 10 base-pair DNA duplex was characterized kinetically to show how simulated sensorgrams generated by the BiaEvaluation software provided by Biacore™ could really improve the design of SPR assays performed with the SCK method. The DNA duplex was investigated at three temperatures, 10, 20 and 30°C, to analyze fast and slow rate constants. The results show that after a short obligatory preliminary experiment, simulations provide users with the best experimental conditions to be used, in particular, the maximum concentration used to reach saturation, the dilution factor for the serial dilutions of the sample injected and the duration of the dissociation and association phases. The use of simulated single-cycle kinetics saves time and reduces sample consumption. Simulations can also be used to design SPR experiments with ternary complexes.

Improved gas sensing performances in SPR sensors by transducers activation

In this paper, among all transduction methodologies reported in the field of solid state chemical sensors, the attention has been focused onto the optical sensing characterization by using surface plasmon resonance (SPR) technique and its evolution towards active plasmonics. Activation of the transducer by application of an oscillating magnetic field in a transversal configuration is demonstrated to improve the gas sensing performance of classical SPR sensors. To this purpose a new transducer, composed of metallic and magnetic materials and a proper sensing layer have been chosen. TiO2 sensing layers have been prepared by two different experimental routes and their optical and morphological features investigated and correlated with their sensing performances. A comparison between classical SPR technique and a new sensing probe based onto magneto-plasmonic effect in resonance condition has been reported. Improved gas sensing performance in terms of sensitivity has been demonstrated in the presence of different alcohol vapours concentration mixed in dry air.

Nanostructured substrates for portable and miniature SPR biosensors

Surface plasmon resonance (SPR) biosensing has matured into a valuable analytical technique for measurements related to biomolecules, environmental contaminants, and the food industry. Contemporary SPR instruments are mainly suitable for laboratory-based measurements. However, several point-of-measurement applications would benefit from simple, small, portable and inexpensive sensors to assess the health condition of a patient, potential environmental contamination, or food safety issues. This Trend article explores nanostructured substrates for improving the sensitivity of classical SPR instruments and nanoparticle (NP)-based colorimetric substrates that may provide a solution to the development of point-of-measurement SPR techniques. Novel nanomaterials and methodology capable of enhancing the sensitivity of classical SPR sensors are destined to improve the limits of detection of miniature SPR instruments to the level required for most applications. In a different approach, paper or substrate-based SPR assays based on NPs, are a highly promising topic of research that may facilitate the widespread use of a novel class of miniature and portable SPR instruments.

Contribution of gold nanoparticles to the signal amplification in surface plasmon resonance

Gold nanoparticle labelling has been shown to produce a remarkable improvement in sensitivity for small molecule detection based on Surface Plasmon Resonance (SPR) bio-sensing. The LSPR (localised SPR)-SPR coupling effect and size/mass-material properties associated with gold nanoparticles are the two main factors to change the SPR resonance condition and cause the enhancement. In this paper we examine the separation of these factors in the context of a classical SPR bio-interaction assay format, and consider the implications on the design of biodetection systems to maximise response. The coupling effect plays a distance dependent role, which allows it to be mapped. The dominant enhancement associated with this factor only occurs within ∼8 nm for a 20 nm gold nanoparticle and is changing by ∼7 nm wavelength shift/nm distance from the Au SPR thin film. Beyond this distance, the size/mass associated with the nanoparticle itself dominates the enhancement. This is demonstrated in a 20-mer DNA sequence sandwich detection, where the enhancement ratio between the coupling effect and the mass is ∼1.5 : 1. This simple method for deconvolution of the mass and coupling effects allows consideration of formats with LSPR nanoparticle labelling for small molecule detection and the best design of the labelling geometry.

Surface plasmon resonance spectro-imaging sensor for biomolecular surface interaction characterization

Surface plasmon resonance (SPR) techniques have become, over the last ten years, powerful tools to study biomolecular surface interaction kinetics in real-time without any use of labels. The highest resolution is currently obtained using spectroscopic SPR systems through the measurement of the complete surface plasmon resonance curve in angular or spectral configuration. But, these systems are limited to a few independent channels (<10). In order to expand their capability to an array format, SPR sensors have also been developed in an imaging mode, allowing parallel monitoring of hundreds of sensing spots onto a camera. However, such sensors rely on the intensity variation measurement at a single position of the resonance spectrum, hence resulting in smaller resolution. We present in this work a SPR spectro-imaging system which aims at keeping the advantage of a mono-channel SPR sensor based on the full resonance curve measurement while introducing an additional spatial dimension (linear multi-spot array). The system is based on the illumination of a biochip through a vertical slit (y-dimension) by a white light source. The reflected light spectrum obtained through a diffracting grating is then imaged on the x-dimension of the camera. The complete spectral resonance curve of a full column of sensing spots can be monitored in parallel and in real-time. We demonstrate that data processing is key to reduce the noise and to improve the resolution. We report on the detection of signals with resolution comparable to the one obtained with a classical SPR mono-channel spectroscopic sensor (3.5×10−7 Refractive Index Unit), gaining an order of magnitude compared to SPR imaging sensors. Eventually, we show that short base DNA–DNA hybridizations with concentrations as low as 100pM can be detected and discriminated in a few tens of minutes following injection by the SPR spectro-imaging system.

Cavity Plasmon Resonance Biosensing

Surface plasmon resonance (SPR) spectroscopy has demonstrated unprecedented performance in label-free real-time probing of various biopolymer, ligand, protein, and DNA interactions. Since its inception in the late sixties, the basic physical phenomenon underlying the SPR biosensing remained unchanged, namely, resonant absorption of TM-polarized light incident upon a metallic nanofilm above the critical total internal reflection angle. Since the SPR field is strictly confined to the metal-analyte interface, the measurements are usually limited to molecular adsorbates located in an immediate vicinity of this surface. Herein, we propose a novel biosensing method utilizing cavity plasmon resonance (CPR) excitation in nanofilms. As opposed to the classical TM-polarized SPR, the CPR is applicable for both TE and TM polarizations and does not require complicated evanescent field excitation conditions. It holds a promise for highly sensitive real-time probing of scalable amounts of analytes in a variety of frequency bands.

Surface Plasmon Resonance: Theoretical Evolutionary Design Optimization for a Model Analyte Sensitive Absorbing-Layer System

Surface plasmon resonance (SPR) has been widely used in a Kretschmann configuration to study optical thickness changes of layers on a Au surface in response to an analyte. The method has been popularized and optimized for protein layers, but has also been used in the same format for other layers without further optimization including those absorbing at the incident wavelength. In this paper, we examine whether SPR remains the "best"attenuated reflectivity format for absorbing overlayers. Experimental data from the SPR response of a copper phthalocyanine film to nitrogen dioxide are used as an input example for a design process using an evolutionary algorithm. The data showed a trend toward thinner gold layer systems ( approximately 25 nm gave an contrast-enhancement of 42.9% compared with approximately 50-nm Au) or Au-free solutions including a layer with low refractive index. From the evolutionary design predictions, further modification could be tested based on available materials and "redundant layers" could be eliminated from the final selection. By inclusion of the external optics, a design could be selected to accommodate poor precision (+/-0.5 degrees ) in the incident angle and a possible multilayer solution was shown using Teflon AF 1600, with refractive index approximately 1.3. The predicted NO(2) response showed an improvement compared with the classical SPR configuration, and the incident angle chosen by the SGA for the interrogation of these layers was close to a stationary point in the absolute response curve, thus offering very good tolerance to automatic position referencing to the reflectivity minimum.

Surface plasmon resonance of azobenzene‐incorporated polyelectrolyte thin films as an H+ indicator

AbstractAn azo‐dye‐incorporated polyionene was spin‐coated as thin films on silver evaporated glass substrates. The films were used in conjunction with surface plasmon resonance (SPR) spectroscopy to examine the utility of combining these techniques for optical H+‐ion sensing. A method suggested by Kano and Kawata was used to enhance the sensitivity of the classical SPR measurements toward absorption detection. With the exposure of the composite polyionene films to HCl vapor, changes in the reflectivity signal were obtained in proportion to the concentration of H+ ions and according to the analyzing wavelength. The transformation of the parent azobenzene into the azohydrazone polar form determined the displacement of the absorption band and was the basis for the absorption‐enhanced SPR measurements. The difference in the SPR signals for the neutral sample and that exposed to interaction with HCl was most demonstrated for the wavelength at which the sample spectrum changed from being nonabsorbing to absorbing. The results show that chromophoric polyionenes are good materials for the production of sensitive substrates and can be combined with SPR spectroscopy for the optical sensing of aggressive gaseous species. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1459–1464, 2002

Temperature-controlled surface plasmon resonance in VO_2 nanorods

The optical properties of VO(2) nanoparticles formed in an amorphous SiO(2) host by stoichiometric ion implantation of vanadium and oxygen and thermal annealing have been determined and correlated with the particle size and morphology. The results show that that the temperature-controlled semiconductor-to-metal phase transition of the VO(2) nanophase precipitates turns on the classical surface plasmon resonance, with specific features that depend on the size and aspect ratio of the VO(2) particles. This effect improves the optical contrast between the metallic and semiconducting states in the near-IR region of the spectrum as a result of dielectric confinement that is due to the SiO(2) host. A fiber-optic application is demonstrated, as is the ability to control the characteristics of the phase transition by using ion implantation to dope the VO(2) nanoparticles with tungsten or titanium ions.