• Journal of Sensor Science and Technology
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• v.24 no.6
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• pp.423-428
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• 2015

A bimetallic chip made of gold and silver was investigated in intensity interrogation mode to confirm enhancement of the SPR sensor resolution. Both reflectance curves of the bimetallic chip and the conventional gold chip was acquired and compared. The line width of the reflectance curve of the bimetallic chip was narrower than that of the conventional Au chip, resulting in steeper tangential slope. The reflectance was monitored at the angle related to the steepest tangential slope. The change in reflectance of the bimetallic chip was larger than that of the Au chip. The critical angle was analyzed by differentiating the reflectance with respect to incident angle twice. Acquiring the critical angle regarding to the sample informs the refractive index of the sample. Using various concentration of Bovine Serum Albumin, we confirmed that refractive index was linearly related to variation of reflectance of the bimetallic chip.

• Applied Chemistry for Engineering
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• v.30 no.3
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• pp.379-383
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• 2019

The capability of detecting amyloid beta 42 ($A{\beta}42$), a biomarker of Alzheimer's disease, using a thiolated protein A-functionalized bimetallic surface plasmon resonance (SPR) chip was investigated. An optimized configuration of a bimetallic chip containing gold and silver was obtained through calculations in the intensity measurement mode. The surface of the SPR bimetallic chip was functionalized with thiolated protein A for the immobilization of $A{\beta}42$ antibody. The response of the thiolated protein A-functionalized bimetallic chip to $A{\beta}42$ in the concentration range of 50 to 1,000 pg/mL was linear. Compared to protein A without thiolation, the thiolated protein A resulted in greater sensitivity. Therefore, the thiolated protein A-functionalized bimetallic SPR chip can be used to detect very low concentrations of the biomarker for Alzheimer's disease.

• Journal of Sensor Science and Technology
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• v.25 no.4
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• pp.243-246
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• 2016

The characteristics of a bimetallic surface plasmon resonance (SPR) chip were investigated to detect a tumor biomarker, carcinoembryonic antigen (CEA). The linewidth and the tangential slope of the reflectance curve of the bimetallic SPR chip was compared with those of the reflectance curve of a conventional gold (Au) SPR chip. The changes in reflectance in response to the variation in CEA in the critical concentration range were analyzed at an angle where the tangential slope of the reflectance curve was maximum. From linear regression analysis, the sensitivity of the bimetallic SPR chip with respect to the CEA in critical concentration was obtained.