Detection of amyloid-β42 using a waveguide-coupled bimetallic surface plasmon resonance sensor chip in the intensity measurement mode.

Yeon Kyung Lee,Won Mok Kim,Kyeong-Seok Lee,Young-Soo Sohn,Wei-Chun Chin

doi:10.1371/journal.pone.0098992

Yeon Kyung Lee, Won Mok Kim + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0098992

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Abstract

The waveguide-coupled bimetallic (WcBiM) surface plasmon resonance (SPR) chip had been utilized in the intensity interrogation detection mode to detect amyloid-β42 (Aβ42), a biomarker of the Alzheimer disease. The SPR reflectance curve of the WcBiM chip has the narrower full-width-at-half-maximum (FWHM) compared with the SPR reflectance curve of the conventional gold (Au) chip, resulting in the steeper gradient. For the enhancement of resolution, the light source was fixed at an angle where the slope of the reflectance curve is the steepest, and the change in the reflectance was monitored. For the detection of Aβ42, the antibody of Aβ42 (anti-Aβ42) was immobilized on the WcBiM SPR chip using the self-assembled monolayer. The SPR responses, the average changes in the reflectance to the Aβ42 at the concentrations of 100 pg/ml, 250 pg/ml, 500 pg/ml, 750 pg/ml, 1,000 pg/ml, and 2,000 pg/ml were 0.0111%, 0.0305%, 0.0867%, 0.1712%, 0.3021%, and 0.5577%, respectively, for the three replicates. From linear regression analysis, the calibration curve indicated that the SPR response had a linear relation with Aβ42 with the concentration in the range of 100 pg/ml to 2,000 pg/ml. A control experiment showed the anti-Aβ42-modified surface of the WcBiM chip had a high specificity to Aβ42. Thus, the enhanced resolution by utilizing the WcBiM SPR chip in the intensity interrogation detection mode aids the diagnosis of the Alzheimer disease by detecting the Aβ42 around the criteria concentration (500 pg/ml) without any labeling.

Highlights

The rapid development of medical technologies has led to an aging society, and the rate of the incidence of dementia is increasing [1]
Since the outer surface of the waveguide-coupled bimetallic (WcBiM) is comprised of Au metal, which is exactly the same metal that is used for the commercialized Au chip, the commercialized Au chip was utilized to carry out the high-density immobilization test of anti-Ab42 with another surface plasmon resonance (SPR) sensor (SPRmicro, K-MAC; Daejeon, Korea) in order to help insure easy data acquisition
We have investigated the characteristics of the WcBiM chip for the detection of Ab42 in order to diagnose Alzheimer disease (AD)

Summary

Introduction

The rapid development of medical technologies has led to an aging society, and the rate of the incidence of dementia is increasing [1]. Throughout the world, Alzheimer disease (AD) is one of the most frequently diagnosed types of dementias. It is estimated that about 80 million people across the globe will be diagnosed with AD by 2,050 [2,3], and the AD-related social medical costs will increase. Early diagnosis of diseases, including AD, is emphasized for successful prognosis and prevention. Identification and monitoring of diseases are essential for maintaining a high quality of human life. A high quality of life can be attributed to better treatment, improvements in survivability, and low medical costs [4,5]. Biosensors provide fast and accurate detection and can serve as a crucial tool in the early diagnosis of a disease [6,7,8]

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