Engineered Core–Shell Multifunctional Nano‐Tracer in Raman‐Silent Region with Highly Retained Affinity to Enhance Lateral Flow Immunoassays

Abstract

measurements and have recently attracted considerable interest in food safety, medical diagnosis, and environmental monitoring. [1] Among the available diagnostic tools, lateral flow immunoassays (LFIAs) dominated POC field during the past decades due to they are arguably the simplest, cheapest, and user-friendly paper-based POC tests. [2] Thanks to the enhanced Raman scattering of reporters adsorbed on noble metal substrate, the fusion of LFIAs with surface-enhanced Raman scattering (SERS) allow the narrow bandwidth, satisfactory photostability, and signal-readout enormously amplified that permit ultrasensitive analysis. [3] Nevertheless, both conventional Raman reporters, biological species, and nitrocellulose (NC) membrane display multiple spectral bands in the fingerprint region (<1800 cm −1 ), which are generally overlapped and difficult to separate (particularly at weakly test-line), thus compromising the performance and increasing analysis difficulty. [4] To efficiently eliminate interference in the fingerprint region, several chemical groups including nitrile, deuterium, and alkyne have been synthesized as backgroundfree Raman reporters with distinctive signals in the biologically silent region (1800-2800 cm −1 , where neither conventional Raman reporters nor biomolecules do not possess any Raman signal). [5] However, the complicated chemosynthesis and Stimulated surface-enhanced Raman scattering (SERS) in combination with engineered nano-tracer offers extraordinary potential in lateral flow immunoassays (LFIAs). Nonetheless, the investigation execution of SERS-LFIA is often compromised by the intricacy and overlap of the Raman fingerprint spectrum as well as the affinity-interference of nano-tracer to antibody. To circumvent these critical issues, an engineered core-shell multifunctional nano-tracer (named APNPs) with precise control of the size of nano-core (AuNPs) and coating of the nano-shell (Prussian blue nanomaterials) is prepared for SERS-LFIA via a modified enlarging particle size and coating modification strategy. Importantly, this nano-tracer exhibits enhanced coupling efficiency, highly retained affinity, reinforced colloid stability, and unique SERS signal (2156 cm −1 ) in the silent region (1800-2800 cm −1 ) with high signal-tobackground ratio simultaneously, all of which are beneficial to the enhancement of the analysis performance. With a proof-of-concept demonstration for detection of ractopamine (RAC), a dual-pattern LFIA that synergizes both the enlarged particle size and coating modification supported colorimetric/biological silence Raman dual-response (coined as the ECCRD assay) is demonstrated by integrating APNPs with the competitive-type immunoreaction. This research may contribute to the rational design of multifunctional nano-tracer, and the ECCRD assay can be expanded for a wide spectrum of applications in environmental monitoring and biomedical diagnosis.

Nature-Derived Hollow Micron-Tubular Signal Tracers Conquering the Size Limitations for Multimodal Immunochromatographic Detection of Antibiotics

“…The K D and k a were measured by indirect enzyme-linked immunoassay (in-ELISA). 28,29 The k a was calculated by the following formula:…”

“…Thanks to the multisignal features of functional materials, the fusion of ICA and STAs not only significantly improves the capability of environmental adaptation and quantitative readout, but also overcomes the drawbacks of the single detection mode. − Desirable STAs to achieve the multireadout ICA with significant performance should possess the following four properties. (1) The proposed STAs should have various excitation modes, allowing generation of more than one signal to provide mutual verification capability and environmental adaptability.…”

An Artificial Miniaturized Peroxidase for Signal Amplification in Lateral Flow Immunoassays

“…[21,22] Recent studies have therefore focused on developing signal enhancement strategies. [23][24][25][26] There are too many of these works to discuss in detail here, but some notable methodologies include: enlargement of the particle size by silver coating, [27] coating the AuNPs with a catalytic metal, [28,29] varying the geometry of the LFiA components, [30] engineering core-shell multifunctional AuNPs, [31] and tuning the flow rate using wax barriers. [32,33] Also, many efforts have been devoted to achieving signal amplification with enzyme-catalyzed chemical reactions, [34] exploiting the activity of enzymes on AuNP surfaces to convert substrates into colored products.…”

Supramolecular recognition enhanced electrochemical sensing: β-cyclodextrin and Pd nanoparticle co-decorated 3D reduced graphene oxide nanocomposite-modified glassy carbon electrode for the quantification of ractopamine

“…Long-term consumption of meat with RAC residues may lead to muscle tremors, limb numbness, arrhythmia, chromosomal abnormalities, and even cause malignant tumors. [3][4][5][6] Nevertheless, in general, residual RAC in animal tissues is difficult to be eliminated from the biological system. Accordingly, for the purpose of ensuring the safety of consumers, there is an urgent and challenging requirement to develop a simple and efficient method for detecting RAC residues in animal products.…”