We report the development of ah ighly sensitive ratiometric fluorescent lateral flowi mmunoassay( RFLFIA) strip for rapid and accurate detection of acute myocardial infarction biomarker,n amely heart-type fatty acid binding protein (H-FABP). The RFLFIA strip works in terms of ratiometric change of fluorescence signal, arising from blending of fluorescence emitted by two composite nanostructures conjugated to capture and probe antibodies and inner filter effect of gold nanoparticles.Inconjunction with using custom smartphone-based analytical device and tonality analysis, quantitative detection of H-FABP was achieved with al ow limit of detection at 0.21 ng mL À1 .T he RFLFIA strip can generate av isually distinguishable green-to-red color change around the threshold concentration of H-FABP (6.2 ng mL À1 ), thus allowing the semi-quantitative diagnosis by the naked eye.

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.

Antibiotics abuse has caused various problems threatening human health and ecological environment. Monitoring antibiotics residual levels is of great significance, yet still challenging for quantitative point-of-need testing with high-sensitivity and visual capability. Here we developed a competitive lateral flow immunoassay (CLFIA) platform with flexible readout for enrofloxacin (ENR), a regularly added antibiotic. To overcome the limitation of low sensitivity of traditional colloidal gold-based CLFIA, the three-dimensionally assembled gold nanoparticles (AuNPs) within dendritic silica scaffold were fabricated as signal reporters. The assembly structure effectively retained the intrinsic absorption features of hydrophobic AuNPs and greatly enhanced the light extinction ability of a single label for signal amplification. The obtained CLFIA strips can not only achieve qualitative screening of ENR at a very low concentration by naked eye (cutoff value: 0.125 ng/mL), but also enable ultrasensitive quantification of ENR by an optical scanner (limit of detection: 0.00195 ng/mL) or a smartphone (limit of detection: 0.0078 ng/mL). Moreover, to elaborate the visual inspection degree of CLFIA against traditional yes/no interpretation, a novel multirange gradient CLFIA strip was prepared for visually semiquantitative identification of ENR with four concentration ranges. The novel CLFIA platform demonstrated sensitive, specific, and reliable determination of ENR with flexible signal readout and provides a potential and invigorating pathway to point-of-need immunoassay of antibiotics.

Sensitive and specific point-of-care detection of methamphetamine in urine was achieved using novel structured gold nano-labels for signal amplification.

We report the development of ah ighly sensitive ratiometric fluorescent lateral flowi mmunoassay( RFLFIA) strip for rapid and accurate detection of acute myocardial infarction biomarker,n amely heart-type fatty acid binding protein (H-FABP). The RFLFIA strip works in terms of ratiometric change of fluorescence signal, arising from blending of fluorescence emitted by two composite nanostructures conjugated to capture and probe antibodies and inner filter effect of gold nanoparticles.Inconjunction with using custom smartphone-based analytical device and tonality analysis, quantitative detection of H-FABP was achieved with al ow limit of detection at 0.21 ng mL À1 .T he RFLFIA strip can generate av isually distinguishable green-to-red color change around the threshold concentration of H-FABP (6.2 ng mL À1 ), thus allowing the semi-quantitative diagnosis by the naked eye.

A reliable ratiometric nanoprobe with two reversible fluorescent signal changes has been constructed for high-sensitivity visual melamine quantification.

No abstract