Encyclopedia of Cancer

2017 Edition
| Editors: Manfred Schwab

Surface Plasmon Resonance

Reference work entry
First Online:
DOI: https://doi.org/10.1007/978-3-662-46875-3_5595
Download entry PDF
How to cite

Definition

Surface plasmon resonance (SPR) is one of several optical phenomena known to occur on two-dimensional metal surfaces (typically gold or silver films) when a total internal reflection of incident light occurs at the interface of two different substances, one with a high refraction index and the other with a low refraction index. The SPR biosensor, which exploits the SPR phenomenon, is a label-free and surface-sensitive spectroscopic system, which utilizes measured changes in the local refraction index upon adsorption. This sensor may be applicable to disease diagnostics and high-throughput screening (HTS) in drug discovery, as well as to studies of biomolecular interaction.

Characteristics

Detection Principle of SPR Biosensor

Surface plasmon polaritons (SPPs), which are also referred to more simply as surface plasmons (SPs), are longitudinal and collective oscillations of electrons occurring on a metal-dielectric interface. The frequencies of these longitudinal oscillations are linked to the wave vector (ksp) by a dispersion relation. The incidence of light can induce the excitation of the SPs when the momentum of the SPs matches that of the incident light. In such cases, the well-characterized surface plasmon resonance phenomenon occurs. As SP waves are inherently longitudinal, the waves can be coupled only with the transverse magnetic (TM) mode of electromagnetic waves, the polarized direction of which is parallel to the incident plane. It has been determined that this wave-matching condition can be quite readily disrupted by even miniscule changes in the interface conditions. Hence, in cases in which the light excitation condition is fixed, the SPR technique not only allows for the precise measurement of changes in the refractive index or the thickness of the medium adjacent to the metal film but also enables the detection of changes in the adsorption layer on the metal surface. As is shown in Fig. 1a, the surface plasmons have a larger wave vector than do light waves of the same energy ≤ ω. In order to excite the SPs with photons, the wave vector of the photons must be increased. Thus far, two basic apparatus can be utilized to achieve this: (i) a prism coupler and (ii) a grating coupler. The Kretschmann geometry of the ATR method, using a prism, is currently the approach most often employed in SPR sensors. This is a special case of ATR in which a thin metal film exists at the ATR interface. As can be observed in Fig. 1b, the light wave is reflected completely at the interface, and excites the SP via the evanescent field. Detection is thus accomplished by recording the changes in the resonance angle or the wavelength.
Surface Plasmon Resonance, Fig. 1

(a) The dispersion relation of non-radiative SPs, and (b) the configuration of the ATR method. See text for details

Properties of the SPR Biosensor

As has been thoroughly documented, the SPR biosensor is a versatile optical spectroscopic system and represents a promising technology for the real-time, label-free analysis of affinity-based measurements in the fields of analytical biochemistry, experimental biology, and medicine. Following the introduction of the SPR biosensor by Jonsson et al. in 1991, the applications of SPR technology have expanded significantly, coming to encompass a wide-ranging field of topics. However, the applications of SPR technology in biomedical science are particularly salient; as many as 5,000 review and research articles concerning SPR have been published over the last 15 years. SPR-based biosensor technologies remain a subject of intensive research, and technical advances in the approach are continually opening new opportunities for the application of the general method. Numerous SPR apparatus are being developed and exploited on the basis of theoretical developments. One such promising approach is the coupling of SPR to mass spectrometry (SPR-MS), an approach that may prove to be extraordinarily useful in the field of functional proteomics. This hybrid SPR-MS system has shown itself to be a rapid and effective method for the identification of interaction partners in complex biological mixtures. The other principal SPR-associated technology involves the application of the technique to imaging systems. With regard to SPR imaging (SPRI), this system detects the change in the reflectivity of incident light, due to the binding of biomolecules to chip surfaces at a fixed angle of incidence, in contrast to SPR systems involving the detection of shifts in the SPR angle or wavelength. SPR imaging using optical array detectors appears to constitute a promising new direction in parallel or multichannel biosensing and thus may allow for high-throughput drug screening. Additionally, SPRI technology may also be applicable to the diagnosis of different types of disease including human cancers in the near future. Currently, commercially obtainable SPR instruments are large and expensive and are therefore inappropriate for applications requiring portability and affordability, such as point-of-care technology (POCT). For this reason, miniaturization efforts that render the development of a portable system feasible have been undertaken in parallel with other components of research into more advanced SPR instrumentation.

Biomedical Applications

The most extensively employed application of SPR sensor technology is the monitoring of affinity scale in the study of biomolecular interactions. The many SPR-based affinity analysis applications currently available have become extremely significant in biomedicine and other fields. Biomedical applications of SPR can be categorized into three general fields; (i) biomolecular interaction analysis, (ii) high-throughput screening, and (iii) proteomics research.

Biomolecular Interaction Analysis (BIA)

The most common application of SPR biosensors is biomolecular interaction analysis (BIA), a critical component of protein function research. SPR technology has been applied to the monitoring of a variety of biological events, including kinetic analyses of ligand–receptor interactions, kinetic analyses of DNA binding to proteins with captured DNA, interaction analyses of enzymes with their substrates, dynamic analyses of antigen–antibody binding, epitope mapping, DNA hybridization, and real-time monitoring of DNA manipulation. In addition, the spectral SPR profile has been shown to be influenced by changes in the optical thickness of the sensor metal film, as well as by changes in the refraction index occurring near the metal surface (within ∼200 nm). Because these optical indicators can be affected by structural transitions in proteins, SPR has also been utilized in the characterization of the conformational alterations of immobilized proteins upon binding to small molecules or in a variety of environments.

High-Throughput Screening (HTS)

SPR-based biosensors can be employed not only for the real-time monitoring of the kinetics of ligands with their receptors but also in the development of pharmaceuticals, as SPR can be employed in drug screening procedures for single molecules in drug discovery studies. The application of SPR technology to high-throughput screening (HTS) is another trend in drug screening. SPR systems have been configured into a variety of formats, including array format, multichannel unit format, and SPR imaging (SPRI) format, which allow for simultaneous real-time measurement in the range of hundreds to thousands of binding reactions on the surface of a chip. Despite the profound versatility of SPR technology, SPR biosensors are also known to have a significant drawback that makes them inappropriate for high-throughput screening, as this system does not allow for the analysis of many samples in parallel. By way of contrast, SPR imaging technology using optical array detectors not only allows for high-throughput multiplex analysis but also provides a sensitivity almost identical to that of classical SPR. Therefore, SPR imaging systems are more appropriate for high-throughput label-free detection than any other optical technique. SPR imaging methods allow for the quantitative characterization of biomolecular interactions, including DNA–DNA duplexes and DNA–drug interactions, in an HTS manner. Furthermore, the targeting of single-base mismatches in the alteration of DNA–DNA hybridization properties has been achieved in DNA arrays, using SPRI biosensors. Another technology that uses the SPR imaging system has been applied to the monitoring of real-time interactions of proteins to a DNA-patterned chip surface in a high-throughput manner. For example, this approach has been used for the high-throughput analysis of interactions occurring between the p53 protein and multiple DNA sequences. A novel SPR imaging-based HTS system for anticancer drug discovery was developed by Ro et al. in 2006. In the research, in order to determine whether the SPR imaging system was capable of screening for small molecules that inhibit protein–protein interactions, the interaction between the retinoblastoma tumor suppressor RB1/pTP53 and the human papillomavirus (HPV) E7 protein was selected for use as a model system. The RB-E7 interaction was challenged by the spotting of the RB protein in the presence of the RB-binding peptide (PepC). The SPR imaging results showed that PepC inhibited the RB-E7 interaction in a concentration-dependent manner, thereby indicating that SPR imaging-based HTS technology could potentially provide a versatile tool for the selection of small-molecule inhibitors, via the targeting of protein–protein interactions.

Proteomics Research

One powerful method by which the biological function of most proteins can be anticipated is the identification of the interaction partners of “bait” proteins, which results in the discovery of protein biomarkers for disease diagnosis and drug screening. These functional proteomics studies, including “ligand fishing” from complex biological mixtures, can be performed efficiently using SPR biosensors coupled with mass spectrometry (MS). This combined SPR-MS system, when utilized as a tool for ligand fishing, allows for the identification of interaction partners with the desired drug candidate characteristics, biomarkers in a variety of therapeutic areas, epitopes or antibody-binding sites on protein antigens, and enzyme inhibitors in extracts constructed from diverse organisms. Conventional SPR-MS approaches can be used to characterize unknown proteins that have been captured on the sensor surface, both via SPR technology and by exact direct mass measurement with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS. As SPR detection is nondestructive and non-labeling, the combination of these two systems is quite relevant to possible approaches to the identification of binding partners directly after interaction analysis, followed by mass spectrometric assays. A new analytical protocol, in which SPR is coupled to electrospray ionization (ESI) MS, has created a new opportunity for the identification and secondary characterization of interaction partners. This system is, potentially, an extremely effective method for the identification of novel binding partners. Therefore, the combined SPR-MS system is expected to become a powerful tool in the area of quantitative analysis of functional proteomics, a field which includes large-scale “ligand fishing” assays.

Cross-References

References

  1. Englebienne P, Van Hoonacker A, Verhas M (2003) Surface plasmon resonance: principles, methods and applications in biomedical sciences. Spectroscopy 17:255–273CrossRefGoogle Scholar
  2. Jonsson U, Fagerstam L, Ivarsson B et al (1991) Real-time biospecific interaction analysis using surface plasmon resonance and a sensor chip technology. Biotechniques 11:620–627PubMedGoogle Scholar
  3. Ro HS, Koh BH, Jung SO et al (2006) Surface plasmon resonance imaging protein arrays for analysis of triple protein interactions of HPV, E6, E6AP, and p53. Proteomics 6:2108–2111PubMedCrossRefGoogle Scholar

See Also

  1. (2012) Biosensor. In: Schwab M (ed) Encyclopedia of cancer, 3rd edn. Springer Berlin Heidelberg, p 415. doi:10.1007/978-3-642-16483-5_646Google Scholar
  2. (2012) Electrospray ionization. In: Schwab M (ed) Encyclopedia of cancer, 3rd edn. Springer Berlin Heidelberg, p 1216. doi:10.1007/978-3-642-16483-5_1846Google Scholar
  3. (2012) Label-free analysis. In: Schwab M (ed) Encyclopedia of cancer, 3rd edn. Springer Berlin Heidelberg, p 1967. doi:10.1007/978-3-642-16483-5_3257Google Scholar
  4. (2012) Matrix-assisted laser desorption/ionization-time of flight. In: Schwab M (ed) Encyclopedia of cancer, 3rd edn. Springer Berlin Heidelberg, p 2187. doi:10.1007/978-3-642-16483-5_3555Google Scholar
  5. (2012) P53. In: Schwab M (ed) Encyclopedia of cancer, 3rd edn. Springer Berlin Heidelberg, p 2747. doi:10.1007/978-3-642-16483-5_4331Google Scholar

Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  1. 1.BioNanotechnology Research CenterKorea Research Institute of Bioscience and BiotechnologyYuseongRepublic of Korea