SPR History

Wood's anomalies

Between 1902 and 1912 R.M. Wood (1868-1955) at Johns Hopkins University (Baltimore, USA) noticed that when he shone polarized light onto a metal-backed diffraction grating, a pattern of unusual dark and light bands appeared in the reflected light (1),(2). Although he speculated about how the light, gratings and metal interacted, a clear answer to the phenomenon was not provided.

The first theoretical treatment of these anomalies was by Lord Rayleigh in 1907 (3). He based his "dynamical theory of the grating" on an expansion of the scattered electromagnetic field in terms of outgoing waves only. With this assumption, he found that the scattered field was singular at wavelengths for which one of the spectral orders emerged from the grating at the grazing angle. He then observed that these wavelengths, which have come to be called the Rayleigh wavelengths λR, correspond to the Wood anomalies. Furthermore, these singularities appeared only when the electric field was polarized perpendicular to the rulings, and thus accounted for the S anomalies; for P polarization, his theory predicted a normal behaviour near λR (4).

Wood's later papers, (5),(2) however, suggest that P anomalies could sometimes be observed. Palmer (6),(7) very clearly demonstrated that P anomalies did exist in deeply ruled gratings. Thus, anomalies of both the S and P type were obtainable, but P anomalies were found only on gratings with deep grooves (4).

Wood's anomaly

In the fifties more experimentation was done on electron energy losses in gasses and on thin foils (8),(9). Pines and Bohm suggested (10),(11),(12) that the energy losses were due to the excitation of conducting electrons creating plasma oscillations or plasmons. Further research (9) revealed that the energy loss resulted from excitation of a surface plasma oscillation in which, part of the restoring electric field extended beyond the specimen boundary. Therefore, the presence of any film or contaminant on the specimen surface affects the surface plasma oscillation. This effect was later described in terms of excitation of electromagnetic ‘evanescent’ waves at the surface of the metal, and in the 1970s evanescent waves were described as a means to study ultra-thin metal films and coatings (13).

Surface plasmons

In the late sixties, optical excitation of surface plasmons by means of attenuated total reflection was demonstrated by Kretschmann (14),(15) and Otto (16).

There have been two major approaches to optical excitation of surface plasma waves: attenuated total reflection in prism coupler-based structures and diffraction at diffraction gratings. The application of surface plasma waves excited by the attenuated total reflection method for sensing has been pioneered by Nylander and Liedberg (17). Particularly because of its relative simplicity, this method has been widely applied for characterization of thin films (18),(19) and (bio)chemical sensing (20),(21),(22).

The use of diffraction grating-based systems for SPR sensing has been advocated by Cullen et al. (23). The grating-based surface plasmon resonance (SPR) sensors have been studied as an alternative to prism-based systems (24),(25).

In the 1980s, surfaces plasmon resonance (SPR) and related techniques exploiting evanescent waves were applied to the interrogation of thin films, as well as biological and chemical interactions (18),(26),(27),(28),(20). These techniques allow the user to study the interaction between immobilized receptors and analytes in solution, in real time and without labelling of the analyte. By observing binding rates and binding levels, there are different ways to provide information on the specificity, kinetics and affinity of the interaction, or the concentration of the analyte.

SPR biosensors

In 1980, Pharmacia became interested in SPR and began investigating the possibilities of the technique. In 1984, Pharmacia founded the company Pharmacia Biosensor AB to develop, produce and market a functional SPR-machine. The development of appropriate sensor surfaces by Pharmacia Biosensor (29),(30) and the fabrication of the silicon microfluidic cartridge brought an easy-to-use SPR-machine closer to becoming a reality (31).

In a short period, many publications from Pharmacia Biosensor described the new hydrogel of dextran (29),(30), the correlation between the SPR signal and the RIA assay (32),(33) and gave a description of the BIACORE machine (32),(34). BIACORE instruments make use of a wedge-shaped laser beam and a diode array for detection, which results in no moving parts in the detection unit.

In 1990 the first BIACORE was sold (35). In 1994 a simplified machine, the BIAlite was released. With this machine, the sample handling was manual instead of computer controlled. The development of different, more sensitive and specialized machines gave us the BIACORE X, BIACORE 2000, 3000 and Q for quality control. Other developments involved the way the liquid was handled.

Typically, SPR machines use microfluidic channels with valves to address the sample to different sensor spots. In 2005 the first machine (BIACORE A100) with dynamic addressing was released (36). The four flow channels in the microfluidic cartridge are much wider and have five detection spots in each channel. The spots can be hydrodynamically addressed by changing the flow rate from two inlet channels, one with sample and one with buffer.

Biacore optics

Over the years, different manufacturers developed other SPR systems. The ProteOn XPR36 system from Bio-Rad uses a crisscross 6 x 6-interaction array capable of simultaneous measurements of 36 interactions. Some machines make use of a cuvette system (e.g. the IBIS Biosensor, IAsys Biosensor) in which binding of large cells is possible. Other machines use a resonant mirror to determine the resonance angle (e.g. IAsys Biosensor). The Spreeta Evaluation module of Sensata Technologies, which can be used to make an in-house system, is probably the simplest SPR measuring device.

With the new instruments, the machine control software has greatly improved by taking the scientist by the hand in performing experiments. In addition, the software that analyses the sensorgrams is much better nowadays. For instance, most programs have routines for automatic cleaning and aligning of the curves. From analysing curve by curve, to global analysis of one single dataset, the new software also makes it possible to analyse several datasets consisting of several different analytes in different concentrations at the same time.
However, manufacturers provide software that is dedicated to their machine. The buyer is greatly dependent on the options of the software and it is difficult to reanalyse results with different software programs.

Biacore A100 flow cell


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(2) Wood, R. W. Diffraction gratings with controlled groove form and abnormal distribution of intensity. Philysophical magazine 23: 310-317; (1912).
(3) Lord Rayleigh Dynamical theory of the grating. Proc.Roy.Soc.(London) A79: 399 (1907).
(4) Hessel, A and Oliner, A. A. A new theory of Wood's anomalies on optical gratings. Appl.Opt. 4: 1275 (1965).
(5) Wood, R. W. Anomalus diffracting gratings. Physical Review 48: 928-937; (1935).
(6) Palmer, C. H. Parallel diffraction grating anomalies. J.Opt.Soc.Am. 42: 269 (1952).
(7) Palmer, C. H. Diffraction grating anomalies. II. Coarse gratings. J.Opt.Soc.Am. 46: 50- (1956).
(8) Ritchie, R. H. Plasma losses by fast electrons in thin films. Physical Review 106: 874 (1957).
(9) Powell, C. J. and Swan, J. B. Effect of oxidation on the characteristic loss spectra of aluminium and magnesium. Physical Review 18: (1960).
(10) Pines, D and Bohm, D. A Collective Description of Electron Interactions. I. Magnetic Interactions. Physical Review 82: 625-634; (1951).
(11) Pines, D and Bohm, D. A Collective Description of Electron Interactions: II. Collective vs Individual Particle Aspects of the Interactions. Physical Review 85: 338-353; (1952).
(12) Pines, D and Bohm, D. A Collective Description of Electron Interactions: III. Coulomb Interactions in a Degenerate Electron Gas. Physical Review 92: 609-626; (1953).
(13) Burstein, E. et al Surface polaritons - propagating electromagnetic modes at interfaces. J.Vac.Sci.Technol. 11: 1004-1019; (1974).
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(16) Otto, A. Exitation of nonradiative surface plasma waves in silver by the method of frustrated total reflection. Z Phys 216: 398-410; (1968).
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(19) Peterlinz, K. A. and Georgiadis, R. Two-color approach for determination of thickness and dielectric constant of thin films using surface plasmon resonance. Opt.Commun. 130: 260-266; (1996).
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(22) Striebel, Ch. et al Characterization of biomembranes by spectral elipsometry, surface plasmon resonance and interferometry with regard to biosensor application. Biosens.Bioelectron. 9: 139-146; (1994).
(23) Cullen, D. C. et al Detection of immunocomplex formation via surface plasmon resonance on goldcoated diffraction gratings. Biosensors 3: 211-225; (1987).
(24) Jory, M. J. et al A surfaceplasmon-based optical sensor using acousto-optics. Measurement Sci.Technol. 6: 1193-1200; (1995).
(25) Lawrence, C. R. et al Surface plasmon resonance studies of immunoreactions utilizing disposable diffraction gratings. Biosens.Bioelectron. 11: 389-400; (1996).
(26) Bernhard, B. and Lengeler, B. Electronic structure of noble metals and polariton-mediated light scattering. (1978).
(27) Flanagan, M. T. and Pantell, R. H. Surface plasmon resonance and immunosensors. Electron Lett. 20: 968-970; (1984).
(28) Nylander, C. et al Gas detection by means of surface plasmons resonance. Sensors and Actuators B 3: 79-88; (1982).
(29) Lofas, S. and Johnsson, B. A novel hydrogel matrix on gold surfaces in surface plasmon resonance sonsors for fast en efficient covalent immobilization of ligands. J.chem.soc., chem commun. 1526-1528; (1990).
(30) Lofas, S. Dextran modified self-assembled monolayer surfaces for use in biointeraction analysis with surface plasmon resonance. Pure & Appl.Chem. 67: 829-834; (1995).
(31) Sjolander, S. and urbaniczky, C. Integrated fluid handling system for biomolecular interaction analysis. Analytical Chemistry 63: 2338-2345; (1991).
(32) Lofas, S. et al Bioanalysis with surface plasmon resonance. Sensors and Actuators B 5: 79-84; (1991).
(33) Stenberg, E. et al Quantitative determination of surface concentration of protein with surface plasmon resonance by using radiolabelled proteins. J.Colloid Interface Sci. 143: 513-526; (1991).
(34) Karlsson, R. et al Kinetic analysis of monoclonal antibody-antigen interactions with a new biosensor based analytical system. Journal of Immunological Methods 229-240; (1991).
(35) Liedberg, B. et al Biosensing with surface plasmon resonance - how it all started. Biosens.Bioelectron. 10: i-ix; (1995).
(36) Safsten, P. et al Screening antibody-antigen interactions in parallel using Biacore A100. Analytical Biochemistry (2006).