Hierarchical Plasmonic-Fluorescent Labels for Highly Sensitive Lateral Flow Immunoassay with Flexible Dual-Modal Switching

Abstract

Lateral flow immunoassay (LFIA), as a prominent point-of-care (POC) test platform, has been extensively adopted for rapid, on-site, and facile diagnosis of pathogen infections and disease biomarkers. Exploring novel structured optical labels of LFIA with amplified signal and complementary detection modes favors the sensitive and flexible POC diagnosis. Here, bimodal labels with both colorimetric and fluorescent readout were fabricated via a layered sequential assembly strategy based on affinity templates and hydrophobic metal-containing nanounits. High-quality colorimetric and fluorescent nanoparticles were densely incorporated into the colloidal supports and confined in separated regions, without interfering with each other. The hierarchical integration of gold nanoparticles and quantum dots with high loading density and good optical preservation realized dual readout and amplified signals from the assemblies of individual single nanoparticles. The "all-in-one" optical labels allowed both colorimetric and fluorescent detection of cystatin C (Cys C) after surface conjugation with antibodies. The LFIA strips revealed noninterfering dual signals for both visual inspection and quantitative detection of Cys C via the naked eye and portable devices, respectively. The limits of detection by colorimetric and fluorescent modes were 0.61 and 0.24 ng mL −1 , respectively. The novel LFIA platform demonstrated sensitive, specific, and reproducible POC testing of biomarkers with flexible detection modes and was reliable for clinical diagnosis.

Quantum dots assembly enhanced and dual-antigen sandwich structured lateral flow immunoassay of SARS-CoV-2 antibody with simultaneously high sensitivity and specificity

“…The iSQS was generated by the reaction of the carboxyl group of SQS-PAA nanospheres with the amino group of RBD to form amide bond. The synthesis step was based on the previous protocol by adopting different nanospheres and antigen ( Huang et al, 2020 ).…”

“…Prior to assembly, the conjugate pad was first treated with optimized blocking buffers and dried at 37 °C. The iSQS reporter, RBD and mouse anti-His antibody were dispersed on the strip according to the previous protocol ( Huang et al, 2020 ). The details are shown in supporting information.…”

“…Therefore, a certain false negative cases would be mistakenly considered as non-infectious, resulting in a huge risk of further transmission in the community ( Chen et al, 2020 ; Huang et al, 2013 ; Koller et al, 2021 ). Compared with colorimetric analysis, the fluorometric LFIA provides improved signal contrast and lower background interference ( Huang et al, 2020 ; Wang et al, 2021 ). Quantum dots (QDs) as an emerging class of fluorescent label exhibit high single-particle brightness, none photo-bleaching and versatile nanostructure engineering for integration and functionalization ( Zhou et al, 2015 ).…”

Advances in nanoparticle‐based lateral flow immunoassay for point‐of‐care testing

“…[ 16 ] QDs can also be doped/encapsuled into or coated on the surface of nanocarriers to further improve the chemical and photo stability, signal intensity, hydrophilicity, and dispersion, bioconjugation capability, and reduce the environmental toxicity. [ 17–20 ] Semiconducting polymer dots have the advantages of biocompatibility, luminescent property, and surface activity, thus, developing rapidly in recent years. [ 21 ]…”

Development of an ultrasensitive fluorescent immunochromatographic assay based on multilayer quantum dot nanobead for simultaneous detection of SARS-CoV-2 antigen and influenza A virus

“…As such, QD nanoprobes can provide intense and quantifiable fluorescence signal for ICA. Moreover, QD beads (QBs) can be fabricated by encapsulating many QDs into a polymer or silica micelles, which can provide high luminescence and stability [ [31] , [32] , [33] , [34] , [35] ]. Thus, integrating high-performance QBs into an ICA system is likely to overcome the deficiencies of traditional ICA method and achieve sensitive detection of respiratory viruses.…”