Citation: Chen, R.; Wang, H.; Zhao,
Y.; Nan, X.; Wei, W.; Du, C.;
Zhang, F.; Luo, Q.; Yang, L.; Xiong, B.
Quantitative Detection of Mastitis
Factor IL-6 in Dairy Cow Using the
SERS Improved Immunofiltration
Assay. Nanomaterials 2022, 12, 1091.
https://doi.org/10.3390/
nano12071091
Academic Editors: Ki-Hyun Kim and
Deepak Kukkar
Received: 8 March 2022
Accepted: 25 March 2022
Published: 26 March 2022
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Article
Quantitative Detection of Mastitis Factor IL-6 in Dairy Cow
Using the SERS Improved Immunofiltration Assay
Ruipeng Chen
1,
*, Hui Wang
1
, Yiguang Zhao
1
, Xuemei Nan
1
, Wensong Wei
2
, Chunmei Du
1
, Fan Zhang
1
,
Qingyao Luo
1
, Liang Yang
1,
* and Benhai Xiong
1,
*
1
State Key Laboratory of Animal Nutrition, Institute of Animal Science,
Chinese Academy of Agricultural Sciences, Beijing 100193, China; wanghui_lunwen@163.com (H.W.);
zhaoyiguang@caas.cn (Y.Z.); xuemeinan@126.com (X.N.); duchunmeim@163.com (C.D.);
zhangfan19@139.com (F.Z.); luoqingyao@caas.cn (Q.L.)
2
Institude of Food Science and Technology, Chinese Academy of Agricultural Sciences,
Beijing 100193, China; weiwensong@caas.cn
* Correspondence: chenruipeng@caas.cn (R.C.); yangliang@caas.cn (L.Y.); xiongbenhai@caas.cn (B.X.);
Tel.: +86-010-62811680 (B.X.)
Abstract:
Interleukin-6 (IL-6) is generally used as a biomarker for the evaluation of inflammatory
infection in humans and animals. However, there is no approach for the on-site and rapid detection
of IL-6 for the monitoring of mastitis in dairy farm scenarios. A rapid and highly sensitive surface
enhanced Raman scattering (SERS) immunofiltration assay (IFA) for IL-6 detection was developed in
the present study. In this assay, a high sensitivity gold core silver shell SERS nanotag with Raman
molecule 4-mercaptobenzoic acid (4-MBA) embedded into the gap was fabricated for labelling.
Through the immuno-specific combination of the antigen and antibody, antibody conjugated SERS
nanotags were captured on the test zone, which facilitated the SERS measurement. The quantitation
of IL-6 was performed by the readout Raman signal in the test region. The results showed that the
detection limit (LOD) of IL-6 in milk was 0.35 pg mL
−1
, which was far below the threshold value
of 254.32 pg mL
−1
. The recovery of the spiking experiment was 87.0–102.7%, with coefficients of
variation below 9.0% demonstrating high assay accuracy and precision. We believe the immunosensor
developed in the current study could be a promising tool for the rapid assessment of mastitis by
detecting milk IL-6 in dairy cows. Moreover, this versatile immunosensor could also be applied for
the detection of a wide range of analytes in dairy cow healthy monitoring.
Keywords: cow mastitis; interleukin-6 (IL-6); immunofiltration assay (IFA); SERS nanotag
1. Introduction
Mastitis is a widespread disease in dairy cows, which not only great restricts the
development of the dairy industry, but also causes heavy economic losses in the dairy
farming industry. Due to the complex pathogenesis and low cure rate, the incidence
of dairy cow mastitis could be as high as 50~70% in China, and the treatment cost is
nearly 200 million yuan every year [
1
]. Many researchers are devoted to investigating the
underlying biological pathogenesis of mastitis to diagnose and manage this disease
[2–4]
.
Pathogen infection is the main cause of mastitis. When this occurs, cytokines are released
to participate in the immune responses and regulate the local inflammatory reactions [
5
].
Moreover, due to a rapid increase in milk yield in the early lactation stage of dairy cows,
mammary epithelial cells usually secrete some proinflammatory cytokines and trigger
immune responses [
6
]. Consequently, cow mastitis is closely related to the immune response
promoted by inflammatory cytokines.
Cytokines play important roles in the immune system of dairy cows by regulating
various cell physiological functions. In addition, they act as transmitters of cell communication
in the process of inflammation and immune response [
7
,
8
]. As a multifunctional cytokine,
Nanomaterials 2022, 12, 1091. https://doi.org/10.3390/nano12071091 https://www.mdpi.com/journal/nanomaterials
