Facile Fabrication of Highly Quantum Dot/AuNP-Loaded Tags for a Dual-Modal Colorimetric/Reversed Ratiometric Fluorescence Immunochromatographic Assay

Abstract

Developing an easily-prepared, sensitive, and accurate point-of-need immunochromatographic assay (ICA) is significant in food safety screening, clinical diagnosis, and environmental monitoring. However, the current single-modal ICAs are limited in certain instinct drawbacks that restrict analytical performances. Herein, we introduce an ultrasensitive dual-modal colorimetric/reversed ratiometric fluorescence ICA based on facilely prepared immunoprobes with a high loading capacity of red quantum dots and AuNPs. By smartly integrating these red-colored/fluorescent signal probes with an immobilized green quantum dot antigen on the test lines, discrete “turn-on” visual inspection and reversed ratiometric quantification via a portable smartphone-based analyzer were accomplished. As an application, this method was employed to detect 11 phosphodiesterase-5 inhibitors in health foods with ultralow detection limits (0.0028–0.045 ng/mL), high repeatability (coefficient of variations of 0.3–1.91%), and reasonable accuracy (recoveries of 86.6–107%). The proposed method was further validated by the authorized liquid chromatography with tandem mass spectrometry method in actual sample detection. This new assay format can be extended to ultrasensitive flexible detection of other food contaminants, environmental pollutants, or tumor biomarkers within minutes, and it just requires simply prepared signal reporters, easy-to-operate procedures, and a low-cost miniaturized analyzer.

Sensitive and on-Site Detection of Staphylococcus aureus Based on CRISPR/Cas 13a-Assisted Chemiluminescence Resonance Energy Transfer

“…The CRISPR/Cas13a system, consisting of Cas13a protein and CRISPR RNA (crRNA), employs crRNA-guided Cas13a endonucleases (Cas13a/crRNA) for RNA targeting, followed by activating a trans cleavage effect with thousands of nonspecific RNA degradation . Given its unique advantages of rapidity, simplicity, and low cost, the immunochromatographic test strip (ICTS) has been considered as one of the most feasible on-site methods and extensively applied in the field of food safety control, disease screening, and environmental monitoring …”

Exonuclease III/Cas12a Cascade Amplification Strategy and Smartphone-Based Portable Fluorescence Detector to Repurpose the Commercial AFP Strip for the POCT of Multiple RNAs

“…Furthermore, the ratio of fluorescence signals from the test line to the control line (F T /F C ) was adopted as the final output, helping minimize external disturbances and improve detection accuracy. 27 As a proof of concept, we employed the AFP strip and SPFD to construct a novel NA-POCT device for the biosensing of RNA molecules. Since RNAs play essential roles in many biological processes, the POCT is of great value for biomedical research and clinical diagnostics.…”

Electrostatic Adsorption of Dense AuNPs onto Silica Core as High-Performance SERS Tag for Sensitive Immunochromatographic Detection of Streptococcus pneumoniae

“…Given its outstanding advantages of simple operation, real-time analysis, user-friendliness, and low cost, the gold nanoparticle (AuNP)-based immunochromatographic assay (ICA) has dominated the point-of-care testing (POCT) market over the past few decades [ 9 , 10 , 11 ]. However, the inherent defects of colorimetric signals from AuNP including low sensitivity and limited quantitative ability have blocked the further application of the ICA method in trace substance detection [ 12 , 13 , 14 ]. To improve the sensitivity of ICA strip, in recent years, researchers have introduced several kinds of novel signal materials such as fluorescent microspheres, magnetic particles, nano-enzyme materials, and surface-enhanced Raman scattering (SERS) tags to replace the colorimetric signal nanomaterials [ 15 , 16 , 17 , 18 , 19 , 20 ].…”