Heavy Metal Ion Detection Based on Lateral Flow Assay Technology: Principles and Applications

Abstract

Heavy metal ions pose a significant threat to the environment and human health due to their high toxicity and bioaccumulation. Traditional instrumentations, although sensitive, are often complex, costly, and unsuitable for on-site rapid detection of heavy metal ions. Lateral flow assay technology has emerged as a research hotspot due to its rapid, simple, and cost-effective advantages. This review summarizes the applications of lateral flow assay technology based on nucleic acid molecules and antigen-antibody interactions in heavy metal ion detection, focusing on recognition mechanisms such as DNA probes, nucleic acid enzymes, aptamers, and antigen-antibody binding, as well as signal amplification strategies on lateral flow testing strips. By incorporating these advanced technologies, the sensitivity and specificity of lateral flow assays have been significantly improved, enabling highly sensitive detection of various heavy metal ions, including Hg²⁺, Cd²⁺, Pb²⁺, and Cr³⁺. In the future, the development of lateral flow assay technology for detection of heavy metal ions will focus on multiplex detection, optimization of signal amplification strategies, integration with portable devices, and standardization and commercialization. With continuous technological advancements, lateral flow assay technology will play an increasingly important role in environmental monitoring, food safety, and public health.

Keywords: antigen–antibody; environmental monitoring; food safety; heavy metal ion detection; lateral flow assay; nucleic acids.

Figure 1

(a) Schematic diagram of DNA probe-based detection principle. (b) Schematic diagram of aptamer-assisted recognition principle. (c) Schematic diagram of nucleic acid enzyme-mediated analysis principle. (d) Schematic diagram of antigen–antibody immunoassay technique principle.

Figure 2

(a) The sensing principle of the traditional lateral flow strip. (b) The sensing principle of the signal amplified lateral flow strip. (c) The test line and control line of the signal amplified lateral flow strip. Adapted with permission from [55].

Figure 3

Schematic diagram of LFA based on an isothermal amplification strategy for the detection of Hg²⁺ and Ag⁺. Adapted with permission from [60].

Figure 4

Principle of test strip detection: (a) structural diagram; (b) with Pb²⁺; (c) without Pb²⁺. Adapted with permission from [61].

Figure 5

Schematic illustration of LFAA for simultaneous multiple targets detection. (A) The structure of the developed LFAA. (B) In the absence of target, UCNP probes were separately hybridized with the corresponding complementary DNA. (C) In the presence of targets, the aptamers preferentially bonded to the corresponding targets and caused fewer aptamers to be hybridized with complementary DNA, thereby liberating UCNPs and resulting in fluorescence decrease. (D) A smartphone-based portable device is used to read the detection results. (E) The schematic of the smartphone-based portable device. Adapted with permission from [64].

Figure 6

Schematic illustration of (A) colorimetric and (B) lateral flow assay approaches for the detection of Tl(I) and Pb(II) ions. Adapted with permission from [67].

Figure 7

Schematic illustration of the Hg²⁺ detection assay where (A) MNAzyme-based cleavage reaction occurs only in the presence of Hg²⁺ and (B) the reaction products are analyzed by the NALFA strip. Adapted with permission from [69].

Figure 8

Schematic representation of the catalytic and stem-loop signal amplification strategy-based Cu²⁺ lateral flow assay. Adapted with permission from [70].

Figure 9

Characterization and Detection Principle of Cd²⁺ Using AuNS and AuNF-Labeled Lateral Flow Test Strips. (A) Transmission electron microscopy (TEM) image and colloidal solution of AuNS. (B) Schematic diagram of the detection principle for Cd²⁺ using AuNS-based lateral flow test strips. (C) Scanning electron microscopy (SEM) image and colloidal solution of AuNF. (D) Schematic diagram of the detection principle for Cd²⁺ using AuNF-based lateral flow test strips. Adapted with permission from [76].

Figure 10

(a) Illustration of the competitive lateral flow immunoassay. (b) Schematic of the microfiber long-period grating (mLPG) and its fabrication procedure using the electric arc discharge method. (c) Schematic of the encapsulated mLPG with a UV-curable polymer overlay supported by a glass slide. (d) Illustration of the experimental setup for the proposed biosensor. (e) Sensing mechanism of the signal transduction. (f) Spectral change during measurement with the proposed biosensor. Adapted with permission from [77].