The lateral flow immunosensor (LFI) is a widely used diagnostic tool for biomarker detection; however, its sensitivity is often insufficient for analyzing targets at low concentrations. Here, an electrochemiluminescent LFI (ECL‐LFI) is developed for highly sensitive detection of troponin I (TnI) using Ru(bpy)32+‐loaded mesoporous silica nanoparticles (RMSNs). A large amount of Ru(bpy)32+ is successfully loaded into the mesoporous silica nanoparticles with excellent loading capacity and shows strong ECL signals in reaction to tripropylamine. Antibody‐immobilized RMSNs are applied to detect TnI by fluorescence and ECL analysis after a sandwich immunoassay on the ECL‐LFI strip. The ECL‐LFI enables the highly sensitive detection of TnI‐spiked human serum within 20 min at femtomolar levels (≈0.81 pg mL−1) and with a wide dynamic range (0.001–100 ng mL−1), significantly outperforming conventional fluorescence detection (>3 orders of magnitude). Furthermore, TnI concentrations in 35 clinical serum samples across a low range (0.01–48.31 ng mL−1) are successfully quantified with an excellent linear correlation (R2 = 0.9915) using a clinical immunoassay analyzer. These results demonstrate the efficacy of this system as a high‐performance sensing strategy capable of capitalizing on future point‐of‐care testing markets for biomolecule detection.

C-reactive protein (CRP) is used as a general biomarker for inflammation and infection. During stroke and myocardial infarction, CRP increases and is present in a broad concentration range of 1−500 μg/mL. Therefore, full-range CRP detection is crucial to identify patients who need close follow-up or intensive treatment after a heart attack. Here, we report the first attempt to develop an electrochemiluminescent lateral flow immunosensor (ECL-LFI) that allows full-range CRP detection. Ru(bpy) 3 2+ -labeled gold nanoparticles (AuNPs) are used as a CRPtargeting probe and a signal generator; they form sandwich immunocomplexes at the test line of the strip and generate strong ECL emission via a Ru(bpy) 3 2+ /tripropylamine system. The ECL-LFI shows high sensitivity in detecting CRP in spiked serum, with a limit of detection of 4.6 pg/mL within 15 min, and a broad detection range of 0.01−1000 ng/mL, which is 2 orders of magnitude broader than that of conventional colorimetric LFI. The clinical usability of the ECL-LFI was evaluated using 30 clinical serum samples (200 ng/mL to 5 mg/mL), which showed a good linear correlation (R 2 = 0.9896), with a clinical chemistry analyzer. The results suggest that the ECL-LFI holds great potential for CRP detection in point-of-care diagnostics.

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The worldwide spread of coronavirus disease 2019 highlights the need for rapid, simple, and accurate tests to detect various variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The antigen test, based on the lateral flow immunoassay (LFI), is a suitable "first line of defense" test that enables early identification and timely isolation of patients to minimize viral transmission among communities. However, it is generally less accurate than nucleic acid testing, and its sensitivity needs improvement. Here, a novel rapid detection method is designed to sensitively detect SARS-CoV-2 using isolated gold nanoparticle (AuNP)assembled SiO 2 core−satellite nanoparticles (SiO 2 @Au CSNPs). Wellgrown AuNP satellites in the synthesis of SiO 2 @Au CSNPs significantly enhanced their light absorption, increased the detection sensitivity, and lowered the detection limit by 2 orders of magnitude relative to conventional gold colloids. The proposed system enabled highly sensitive detection of the SARS-CoV-2 nucleocapsid protein with a detection limit of 0.24 pg mL −1 within 20 min. This is the first study to develop a highly sensitive antigen test using the absorption-modulated SiO 2 @Au CSNPs. Our findings demonstrate the capacity of this platform to serve as an effective sensing strategy for managing pandemic conditions and preventing the spread of viral infections.

A simple and rapid As3+ detection method using 3-nitro-L-tyrosine (N-Tyr) is reported. We discovered the specific property of N-Tyr, which specifically chelates As3+. The reaction between As3+ and N-Tyr induces a prompt color change to vivid yellow, concomitantly increasing the absorbance at 430 nm. The selectivity for As3+ is confirmed by competitive binding experiments with various metal ions (Hg2+, Pb2+, Cd2+, Cr3+, Mg2+, Ni2+, Cu2+, Fe2+, Ca2+, Zn2+, and Mn2+). Also, the N-Tyr binding site, binding affinity, and As3+/N-Tyr reaction stoichiometry are investigated. The specific reaction is utilized to design a sensor that enables the quantitative detection of As3+ in the 0.1–100 μM range with good linearity (R2 = 0.995). Furthermore, the method’s applicability for the analysis of real samples, e.g., tap and river water, is successfully confirmed, with good recoveries (94.32–109.15%) using As3+-spiked real water samples. We believe that our discovering and its application for As3+ analysis can be effectively utilized in environmental analyses such as those conducted in water management facilities, with simplicity, rapidity, and ease.