Recent Advances in the Immunoassays Based on Nanozymes

Abstract

As a rapid and simple method for the detection of multiple targets, immunoassay has attracted extensive attention due to the merits of high specificity and sensitivity. Notably, enzyme-linked immunosorbent assay (ELISA) is a widely used immunoassay, which can provide high detection sensitivity since the enzyme labels can promote the generation of catalytically amplified readouts. However, the natural enzyme labels usually suffer from low stability, high cost, and difficult storage. Inspired by the advantages of superior and tunable catalytic activities, easy preparation, low cost, and high stability, nanozymes have arisen to replace the natural enzymes in immunoassay; they also possess equivalent sensitivity and selectivity, as well as robustness. Up to now, various kinds of nanozymes, including mimic peroxidase, oxidase, and phosphatase, have been incorporated to construct immunosensors. Herein, the development of immunoassays based on nanozymes with various types of detection signals are highlighted and discussed in detail. Furthermore, the challenges and perspectives of the design of novel nanozymes for widespread applications are discussed.

Keywords: immunoassays; nanozymes; signal amplification; target detection.

Scheme 1

Schematic diagram of (A) classical (traditional) immunoassays based on natural enzyme and (B) current (modified) immunoassays based on nanozyme.

Figure 1

(A) Schematic diagram of PBNP-based sandwich NLISA [26]. Reprinted with permission from ref. [26]. Copyright 2018 American Chemical Society. (B) Scheme of mechanism of catalytic oxidation of TMB by photo-activated TiO₂−CA for the quantitation of ALP [30]. Reprinted with permission from ref. [30]. Copyright 2015 American Chemical Society. (C) Scheme of the cascade reaction for the detection of PSA by FeSA−PtC nanozymes based ELISA [35]. Reprinted with permission from ref. [35]. Copyright 2021 American Chemical Society. (D) Scheme of sandwich-type TLISA for the detection of IL-6 by using TMB NPs [37]. Reprinted with permission from ref. [37]. Copyright 2019 American Chemical Society.

Figure 2

(A) Scheme of the detection principle of cardiac biomarkers based on SANs-lateral flow immunoassay [44]. Reprinted with permission from ref. [44]. Copyright 2021 American Chemical Society. (B) Schematic diagram of mechanism of the simultaneously immunodetection of the BChE activity and total amount of BChE [51]. Reprinted with permission from ref. [51]. Copyright 2018 American Chemical Society. (C) Scheme of nanomaterial-enhanced 3D-printed sensor platform for simultaneous detection of two herbicides [53]. Reprinted with permission from ref. [53]. Copyright 2021 Elsevier.

Figure 3

(A) Schematic diagram of a ratiometric fluorescence ELISA for CRP detection based on MnO2 NFs coupled with CDs [55]. Reprinted with permission from ref. [55]. Copyright 2018 Royal Society of Chemistry. (B) Schematic illustration of the label-free nanozyme-based chemiluminescent immunosensor by using CuONRs for CEA detection [58]. Reprinted with permission from ref. [58]. Copyright 2018 Elsevier. (C) Schematic illustration of CL imaging nanozyme immunoassay of multiple chicken cytokines and an immunosensor array [60]. Reprinted with permission from ref. [60]. Copyright 2018 Royal Society of Chemistry.

Figure 4

(A) Schematic diagram of the construction of electrochemical immunosensing platform by using PtDEN for lung cancer biomarker detection [62]. Reprinted with permission from ref. [62]. Copyright 2020 Elsevier. (B) Schematic of a sandwich-type electrochemical immunosensor for thyroid-stimulating hormone detection using the catalytic ester hydrolysis function of PtNP and AB [64]. Reprinted with permission from ref. [64]. Copyright 2020 Wiley Online Library. (C) Schematic of a near-infrared ECL immunoassay for detection of PRRSV [67]. Reprinted with permission from ref. [67]. Copyright 2017 Elsevier.

Figure 5

(A) Schematic illustration of nanozyme-based ratiometric SERS immunosorbent assay by using AuNPs doped COFs for detection of food allergy proteins [70]. Reprinted with permission from ref. [70]. Copyright 2019 American Chemical Society. (B) Schematic illustration of the CdS/PdPt based PEC immunoassay for CEA detection [72]. Reprinted with permission from ref. [72]. Copyright 2021 American Chemical Society. (C) Schematic illustration of the construction of sandwichtype ultrasensitive PEC immunosensor using a nanozyme with duple enzyme activity [73]. BiOS: Bi10O6S9 nanosheet arrays; 4-CN: 4-chloro-1-naphthol; 4-CD: enzo-4-chlorohexadienone; CYFRA: cytokeratin 19 fragment 21-1. Reprinted with permission from ref. [73]. Copyright 2021 Elsevier.

Figure 6

(A) Schematic diagram of the microfluidic immunosensor for Salmonella detection [75]. Reprinted with permission from ref. [75]. Copyright 2021 American Chemical Society. (B) Schematic illustration of the principle of nanozyme-linked immunosorbent assay for dual colorimetric and ratiometric fluorescent determination of cTnI [76]. Reprinted with permission from ref. [76]. Copyright 2019 Elsevier. (C) Schematic illustration of the proximity hybridization-based multiple stimuli-responsive immunosensing platform for ECL, colorimetry and photothermal sensing of ovarian cancer biomarkers [78]. Reprinted with permission from ref. [78]. Copyright 2020 Elsevier.