Shift Of Surface Plasmon Resonance Wavelength Research Articles

Design considerations for surface plasmon resonance-based fiber-optic detection of human blood group

A fiber-optic surface plasmon resonance (SPR) sensor for the detection of human blood groups is proposed. Previous experimental results describing the wavelength-dependent refractive index variation of multiple samples of different blood groups are considered for theoretical calculations. The spectral interrogation method, along with silica fiber and silver layer, is considered. The sensor's performance is closely analyzed in terms of shift in SPR wavelength and SPR curve width in order to optimize the design parameters for a reliable and accurate blood-group identifier. The sensor design parameters include silver layer thickness, fiber core diameter, sensing region length, and temperature variation. The results are explained in terms of light coupling and plasmon resonance condition. The proposed sensing probe is able to provide high sensitivity and accuracy of blood-group detection, thereby opening an easy and reliable window for medical applications.

Inverted Size-Dependence of Surface-Enhanced Raman Scattering on Gold Nanohole and Nanodisk Arrays

Surface-enhanced Raman scattering (SERS) on gold nanohole and nanodisk arrays with precisely controlled size and spacing fabricated via electron beam lithography was investigated. These nanostructures exhibit strong SERS signals at 785 nm excitation but not at 514 nm. When the edge-to-edge distance is maintained, enhancement increases for nanoholes but decreases for nanodisks as diameter is increased. It is shown that the observed enhancement results from the local surface plasmon resonance wavelength shifts to the near-infrared regime as nanohole diameter increases. The large tolerance on dimensions and the empty space confined by nanoholes suggest promise for their use as a functional component in sensing, spectroscopy, and photonic devices.

Integrated-optic biosensor by electro-optically modulated surface plasmon resonance

We present a new integrated-optic surface plasmon resonance (SPR) biosensor based on electro-optical modulation. The SPR characteristics for the analyte concentration detection can be electro-optically modulated by applying the voltage on the electrodes of the biosensor fabricated on lithium niobate, which is an excellent electro-optic material. Two measurement methods, electro-optically modulated SPR spectral measurement and electro-optically modulated SPR intensity measurement, are demonstrated and their measurands are the SPR wavelength and the output optical intensity, respectively. Human serum albumin is coated on the gold film surface of the proposed biosensor to detect the concentration of beta-blocker, which is a remedy for heart disease. As the applied voltage increases such that the effective index of guided mode rises, the SPR wavelength shifts toward the long wavelength side and the output optical intensity at the wavelength of 632.8 nm diminishes. The linear regression slope of the relation between the measurand and the applied voltage is dependent on the analyte concentration and can be used to determine the concentration variation. Experimental results measured by the electro-optically modulated SPR methods are compared with those measured by the conventional spectral and intensity methods, and the effects of waveguide width on the biosensor performance are discussed.

Development of Protein Chip for Diagnosis of Chlamydophia Pneumoniae

Background; The diagnosis of chlamydial infection is based on serology. The current gold standard of diagnosis is MIF(microimmunofluorescence), but this modality is subjective and time-consuming. Protein microarray with using a SPR(surface plasmon resonance) sensor has recently been suggested as a method for detecting infection. For developing a protein chip to diagnose chlamydial infection, EBs(elementary bodies) were immobilized on a gold chip and the interaction between an antibody for Chlamydophila pneumoniae and the EBs(elementary bodies) immobilized on the surface of the gold chip was measured by using an SPR sensor. Methods; For the surface antigen, the EBs of Chlamydophila pneumoniae LKK1 were purified. Charged arrays were prepared by using PDDA(polydiallyldimethylammonium chloride) which has a positive charge. After immobilization of the chlamydial EBs on the PDDA surface, the investigation of the surface was done with using atomic force microscopy. After the antibody for C. pneumoniae was applied on chip, we monitored the SPR wavelength-shift to detect any antigen-antibody interaction with using a self-assembled SPR sensor. Results; The chlamydial EBs on the positively charged PDDA were visible on the surface with using atomic force microscopy. The SPR wavelength increased after interaction of antibody for C. pneumoniae with the EBs immobilized on charged gold surface. The wavelength-shift was correlated with the concentration of antigens. Conclusion; The surface immobilization of EBs on the gold surface with the charged arrays was identified and the antigen-antibody interaction on the gold chip was detected via the SPR sensor. Further investigations are needed to apply this technique to the clinical field.

Integrated-optic surface-plasmon-resonance biosensor using gold nanoparticles by bipolarization detection

A new integrated-optic surface-plasmon-resonance (SPR) biosensor using gold nanoparticles with the ability of bipolarization interrogation is demonstrated. Although the previous SPR biosensor using gold nanoparticles can excite the surface plasma wave by the TM- and the TE-polarized lightwave, the sensitivity to the environmental index change for the TE-polarized lightwave is too low to be useful. The new integrated-optic SPR biosensor with a ridge waveguide structure can produce the obvious SPR wavelength shifts varied with the analyte concentration for two orthogonal polarizations. Therefore, two kinds of analytes can be separately detected by the TM- and the TE- polarized modes in one SPR biosensor, and the number of detectable biomaterials by the biosensor array in one chip can be doubled. This SPR biosensor is designed for the concentration measurement of beta-blocker, which is a remedy for heart disease. In the linear operation range, the SPR wavelength increases with the concentration of beta-blocker at a rate of 0.073 and 0.029 nm/ppm for the TM- and the TE- polarized modes, respectively.

Analysis of protein interactions on protein arrays by a wavelength interrogation-based surface plasmon resonance biosensor.

We have investigated whether surface plasmon resonance (SPR) sensors based on the wavelength interrogation are able to analyze protein interactions on protein arrays. The spectral SPR sensor was self-constructed and its detection limit, expressed as the minimal refractive index variation, was calculated to be 6.6x10(-5) with the signal fluctuation of 1.0x10(-5). The protein array surface was modified by a mixed thiol monolayer to immobilize proteins. Protein arrays were analyzed by the line-scanning mode of the SPR sensor, which scanned every 100 microm along the central line of array spots and the scanned results were presented by color spectra from blue to red. Glutathione S-transferase (GST)-rac1 caused a concentration-dependent increase of SPR wavelength shift on protein arrays. The surface structure of the protein arrays was analyzed by atomic force microscopy. Specific interactions of antigens with antibodies were analyzed on the protein arrays by using three antibodies and eight proteins. These results suggest that the wavelength interrogation-based SPR sensor can be used as the biosensor for the high-throughput analysis of protein interactions on protein arrays.

Surface Plasmon Resonance Waveguide Biosensor by Bipolarization Wavelength Interrogation

A new surface-plasmon-resonance (SPR) waveguide biosensor with the capability of bipolarization wavelength interrogation is presented. In the conventional SPR biosensors, only the transverse magnetic (TM)-polarized lightwave can couple with the surface plasma wave. The proposed SPR biosensor can make both the TM- and the transverse electric (TE)-polarized lightwave to produce the SPR. Therefore, two kinds of biomaterials can be separately detected by the signals from the TM- and the TE-polarized modes, and the number of detectable materials in a single chip can be doubled. Human serum albumin is coated on the device to sense the concentration of beta-blocker. Experimental results show that the concentration of beta-blocker is related to the SPR wavelength shift at a rate of 0.08 and 0.027 nm/ppm for the TM- and the TE-polarized modes, respectively.

Near-Infrared Surface Plasmon Resonance Measurements of Ultrathin Films. 2. Fourier Transform SPR Spectroscopy

The application of surface plasmon resonance (SPR) measurements to the study of ultrathin organic films adsorbed onto gold surfaces utilizing near-infrared (NIR) excitation from a Fourier transform (FT) spectrometer is described. The FT-SPR experiment measures the NIR reflectivity spectrum from a prism/gold film/water assembly at a fixed angle of incidence approximately 1−2° greater than the critical angle. A strong reflectivity minimum is observed in the FT-SPR spectrum; this minimum can be shifted from 12 000 to 6000 cm-1 by tuning the angle of incidence. Upon adsorption of a thin biopolymer film from solution, a shift in the minimum is observed that can be correlated to a film thickness using Fresnel calculations. From experiments on the adsorption of electrostatically bound poly(lysine)/poly(glutamic acid) multilayers, an ∼60-cm-1 shift per 10-Å change in film thickness was measured. Frequency shifts of 2 cm-1 (corresponding to a thickness change of the polymer layer of ∼0.3 Å) can be easily measured from the FT-SPR spectra, demonstrating that this technique has sensitivity equivalent to or better than other visible SPR angle shift or wavelength shift measurements. Furthermore, the ability to perform FT-SPR measurements over a wide range of NIR wavelengths allows one to avoid any absorption bands that might otherwise interfere with the analysis.

Use of colloidal gold surface plasmon resonance peak shift to infer affinity constants from the interactions between protein antigens and antibodies specific for single or multiple epitopes.

The surface plasmon resonance (SPR) wavelength of colloidal gold particles coated with a monoclonal antibody is red-shifted when the antibody interacts with its specific ligand. This shift results from the change in the refractive index of the particles as induced by ligand binding. This property is used to monitor in real-time the association and dissociation kinetics of the interaction in solution. The monitoring is performed in a clinical chemistry automated analyzer during a few minutes of incubation at 37 degrees C. Data treatment allows calculation of the affinity constant of the interaction. The SPR wavelength shift does not necessarily require agglutination or aggregation of the particles to occur since particles coated with one monoclonal antibody specific for a single epitope on the ligand can be used in the procedure. The affinity constants measured by this procedure correlate with those calculated from Scatchard plots or BIAcore data.