Citation: Li, S.; He, D.; Li, S.; Chen,
R.; Peng, Y.; Li, S.; Han, D.; Wang, Y.;
Qin, K.; Ren, S.; et al. Magnetic
Halloysite Nanotube-Based SERS
Biosensor Enhanced with Au@Ag
Core–Shell Nanotags for Bisphenol A
Determination. Biosensors 2022, 12,
387. https://doi.org/10.3390/
bios12060387
Received: 4 May 2022
Accepted: 30 May 2022
Published: 2 June 2022
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Article
Magnetic Halloysite Nanotube-Based SERS Biosensor Enhanced
with Au@Ag Core–Shell Nanotags for Bisphenol A Determination
Sen Li
1,†
, Defu He
1,2,†
, Shuning Li
1,3
, Ruipeng Chen
1,3
, Yuan Peng
1
, Shuang Li
1
, Dianpeng Han
1
, Yu Wang
1
,
Kang Qin
1
, Shuyue Ren
1
, Ping Chen
2,
* and Zhixian Gao
1,
*
1
Tianjin Key Laboratory of Risk Assessment and Control Technology for Environment and Food Safety,
Tianjin Institute of Environmental and Operational Medicine, Tianjin 300050, China;
lisen2021@foxmail.com (S.L.); hedefu0919@gmail.com (D.H.); lishuning121@163.com (S.L.);
chenruipeng2016@163.com (R.C.); dalidao@139.com (Y.P.); liza3320@163.com (S.L.);
15210520025@126.com (D.H.); wangyuyu9210@163.com (Y.W.); qinkang2020@foxmail.com (K.Q.);
renshuyue2018@163.com (S.R.)
2
School of Food Science and Engineering, Jilin Agricultural University, Changchun 130118, China
3
State Key Laboratory of Food Nutrition and Safety, Tianjin University of Science & Technology,
Tianjin 300457, China
* Correspondence: ccchenping@sina.com (P.C.); gaozhx@163.com (Z.G.)
† These authors contributed equally to this work.
Abstract:
Bisphenol A (BPA) has emerged as a contaminant of concern because long-term exposure
may affect the human endocrine system. Herein, a novel aptamer sensor based on magnetic separation
and surface-enhanced Raman scattering (SERS) is proposed for the extremely sensitive and specific
detection of trace BPA. Moreover, the capture unit was prepared by immobilizing thiolated (SH)-BPA
aptamer complementary DNA on AuNP-coated magnetic halloysite nanotubes (MNTs@AuNPs),
and SH-BPA aptamer-modified Au@4-MBA@Ag core–shell SERS nanotags acted as signal units.
By the complementary pairing of the BPA aptamer and the corresponding DNA, MNTs@AuNPs
and Au@4-MBA@AgCS were linked together through hybridization-ligation, which acted as the
SERS substrate. In the absence of BPA, the constructed aptamer sensor generated electromagnetic
enhancement and plasmon coupling to improve the sensitivity of SERS substrates. Owing to the high
affinity between BPA and the aptamer, the aptamer probe bound to BPA was separated from the
capture unit by an externally-induced magnetic field. Thus, the Raman intensity of the MNTs@AuNP-
Ag@AuCS core–satellite assemblies was negatively correlated with the BPA concentration. High
sensitivity measurements of BPA might be performed by determining the decline in SERS signal
strength together with concentration variations. The proposed aptasensor is a promising biosensing
platform for BPA detection.
Keywords:
surface-enhanced Raman scattering (SERS); aptasensor; bisphenol A; core–satellite assemblies
1. Introduction
Bisphenol A (BPA), also known as 2,2-bis(4-hydroxyphenyl) propane, has a chem-
ical structure similar to that of endogenous estrogens and can mimic or interfere with
endogenous estrogen action to exert estrogenic effects; it is a typical endocrine-disrupting
chemical [
1
]. BPA is a commonly used industrial compound, mainly used in the manu-
facturing of polycarbonates and resins and other products required for daily life, such
as medical equipment and sports items. Refreshments are protected from direct contact
with metals using epoxy resins as an inner coating for cans, commonly used in food and
beverage containers, including milk bottles, and as additives to other plastics [
2
]. Studies
have shown that polymerized BPA molecules found in epoxy resins, bound with ester
bonds, can leach into water and food containers and baby bottles under high-temperature,
acidic, or alkaline conditions and can induce chronic conditions such as diabetes, congenital
Biosensors 2022, 12, 387. https://doi.org/10.3390/bios12060387 https://www.mdpi.com/journal/biosensors
