**4. Applications**

The SPR sensors are available for both concentration and reaction kinetic detections [28]. Their application fields include biological and chemical analyses, drug screening, environmental and food safety monitoring [29].

The concentrations of the biomarkers are essential information for the early diagnose of disease [30]. The reaction kinetics is a crucial parameter for drug screening [31], biological molecules interactions, and chemical industry. The association/dissociation constant is helpful on estimating the strength of the bond [32, 33]. The SPR sensor equipped with different chips affords a friendly condition for the biological molecular reactions. And the chips modified with specific materials (fibronectin, polylysine, and so on) can satisfy the condition for cell culturing [34]. This enlarges the applications of the SPR sensors on biomarker concentration detections, reaction kinetics of molecules, and reaction kinetics between cell membrane and molecules [8].

Natural compounds are usually more biocompatible than synthetic ones, thus they are more suitable drug candidates. But natural compound normally has a low concentration and mixes with other chemicals. The low detection limit and the convenient kinetic detection method make SPR sensors to be widely used in small molecule drug screenings [35]. Furthermore, the high throughput [36, 37] and

*Surface Plasmon Resonance Sensors for Concentration and Reaction Kinetic Detections DOI: http://dx.doi.org/10.5772/intechopen.92549*

mapping technique allow a quick grasp of drugs from natural compounds [22, 23], and even reprocessing of approved drugs.

The contaminants in the environment and food are harmful to our healthy [38, 39]. The SPR sensors not only can detect the concentration of a certain contaminant, but also can make a rough screening of the unknown chemical and biological contaminants. For possible contaminants, the SPR sensor can grasp the molecules or cells for further analyses.

## **5. Summary**

ubiquitous and reliable for most of the concentration calculations, the standard samples normally cannot be obtained for a novel biomarker. This significantly

At a total mass transport limited condition, the binding rate of analytes is

where *C*<sup>0</sup> is the analyte concentration in the bulk solution, and *MW* is the molecular weight of the analyte. At the beginning of the binding process, *C* is zero.

where the value of *dR=dt* approximately is equal to the slope of the curve at the

Bimolecular reaction is the basic reaction in some multistep reaction. For instance, the Eq. (21) can be expressed as Eq. (22), which contains two bimolecular

> <sup>2</sup>*<sup>A</sup>* <sup>þ</sup> *<sup>B</sup>*! *ka*

*<sup>A</sup>* <sup>þ</sup> *<sup>B</sup>* ! *ka*<sup>1</sup>

screening, environmental and food safety monitoring [29].

*kd*1

*kd*

*AB* <sup>þ</sup> *<sup>A</sup>* ! *ka*<sup>2</sup> *kd*2

The SPR sensors are available for both concentration and reaction kinetic detections [28]. Their application fields include biological and chemical analyses, drug

The concentrations of the biomarkers are essential information for the early diagnose of disease [30]. The reaction kinetics is a crucial parameter for drug screening [31], biological molecules interactions, and chemical industry. The association/dissociation constant is helpful on estimating the strength of the bond [32, 33]. The SPR sensor equipped with different chips affords a friendly condition for the biological molecular reactions. And the chips modified with specific materials (fibronectin, polylysine, and so on) can satisfy the condition for cell culturing [34]. This enlarges the applications of the SPR sensors on biomarker concentration detections, reaction kinetics of molecules, and reaction kinetics between cell

Natural compounds are usually more biocompatible than synthetic ones, thus they are more suitable drug candidates. But natural compound normally has a low concentration and mixes with other chemicals. The low detection limit and the convenient kinetic detection method make SPR sensors to be widely used in small molecule drug screenings [35]. Furthermore, the high throughput [36, 37] and

*dt* <sup>¼</sup> *km*ð Þ *<sup>C</sup>*<sup>0</sup> � *<sup>C</sup>* <sup>∙</sup> *MW* <sup>∙</sup> <sup>10</sup><sup>9</sup> (19)

*dt* <sup>¼</sup> *kmC*<sup>0</sup> <sup>∙</sup> *MW* <sup>∙</sup> <sup>10</sup><sup>9</sup> (20)

*A*2*B* (21)

*A*2*B* (22)

hinders the development of the corresponding detection methods.

*dR*

*dR*

*Analytical Chemistry - Advancement, Perspectives and Applications*

decided by the mass transport rate.

Thus, this equation can be expressed as

beginning of the bimolecular interaction.

**3.2 Other reactions**

**4. Applications**

membrane and molecules [8].

**98**

reactions.

The binding and unbinding of analytes on the SPR sensor chip surface induces the refractive index change next to the thin metallic film. Surface plasmon resonance sensors are sensitive to this refractive index change and transfer this change to the shift of the resonance angle. By a real time recording of the angle change, we obtained the SPR signal for data processing.

The bimolecular reaction is a basic reaction on the sensor chip. By making a good match of the simulated and experimental SPR sensorgrams, we obtained the kinetic constants. Furthermore, we also use the SPR sensors on concentration detections. The concentration detection method based on the *R*eq value is sensitive but time consuming. The novel calibration free method based on the curve at the beginning of the binding process is time saving. Besides, it efficiently avoids the demand of standard samples. Although its sensitivity is not high, it is still a promising method.

Right now, SPR sensors have been applied in the field of biological and chemical analyses, drug screening, environmental and food safety monitoring. As its integration with new technologies, the application fields of SPR sensors will be further enlarged.

## **Acknowledgements**

Xiaoying Wang participated in the manuscript writing.
