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Respiratory viruses have become a major global health challenge which would benefit from advances in screening methods for early diagnosis. Respiratory syncytial virus (RSV) is one of the most important pathogen causing severe lower respiratory tract infections. Here we present a novel surface-enhanced Raman scattering (SERS) enzyme-catalyzed immunoassay of RSV by employing peroxidase substrate 3, 3′–5, 5′-tetramethylbenzidine (TMB) as Raman molecule. Horseradish peroxidase (HRP) attached to the detection antibody in a novel sandwich immunoassay catalyzes the oxidation of TMB by H 2 O 2 to give a radical cation (TMB + ), which could be easily adsorbed on the negatively charged surface of silver nanoparticles (AgNPs) through electrostatic interaction, inducing the aggregation of AgNPs and thus giving a strong SERS signal. A linear relationship was obtained between the Raman intensity and the amount of RSV in the range from 0.5 to 20 pg/mL, and the minimum detectable concentration of this SERS-based enzyme immunoassay was 0.05 pg/mL, which was 20 times lower than that found in the colorimetric method. [ABSTRACT FROM AUTHOR]

Abstract Carbon quantum dots (CQDs), prepared by one-step hydrothermal treatment of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and triethylamine (TEA), could be exfoliated or delaminated into single-layered graphene quantum dots (s-GQDs) with methanol for the first time, with fluorescence (FL) emission at 500 nm when excited at 417 nm. The s-GQDs, with more sufficient carboxyl groups on the surface than CQDs, could be induced to be aggregated by metal ion dysprosium (Dy3+), resulting in aggregation-induced emission quenching effect subsequently. However, the presence of phosphate (PO 4 3-) destroys the Dy3+-induced aggregates of s-GQDs owing to the strong coordination between Dy3+ and PO 4 3-, inducing the FL emission recovery of the s-GQDs and providing selective detection method of PO 4 3- in the artificial wetlands with the linear range of 0.2–30 μM and determination limit of 0.1 μM (3σ). Graphical abstract Carbon quantum dots (CQDs) was firstly reported to be exfoliated or delaminated into single-layered graphene quantum dots (s-GQDs) by mixing with methanol followed by evaporating. The s-GQDs with sufficient carboxyl groups on the surface could specifically be induced by metal ion dysprosium (Dy3+) to form aggregates, resulting in aggregation-induced emission quenching effect. However, the presence of phosphate (PO 4 3-) destroyed the Dy3+-induced aggregates of s-GQDs, inducing the FL emission recovery of the s-GQDs, which can be used for sensitive and selective detection of PO 4 3-. fx1 Highlights • Single-layered GQDs (s-GQDs) are easily obtained by exfoliating or delaminating the as-prepared CQDs with methanol. • The s-GQDs with more carboxyl groups on the surface than the CQDs can be induced to generate aggregation-induced emission quenching by Dy3+. • An off-on fluorescent strategy is successfully applied for the highly selective detection of PO43- by using s-GQDs-Dy3+ complex. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) spectra, which can provide large information about trace amount of chemical and biological species have been widely performed as a well-established tool in complex biological system. In this work, coomassie brilliant blue (R-250) with high affinity to proteins and high Raman activity was employed as a Raman reporter to probe prion protein (PrP) through a dual-aptamer mechanism, and thus an original strategy for PrP determination was proposed, which showed great potential to turn on the SERS response through specific recognition of anti-prion aptamers towards the target protein. Aptamers (Apt1 and Apt 2) recognizing distinct epitopes of PrP with high affinity were first conjugated to Ag@Si NPs, and Ag@Si-PrP/R-250-Ag@Si conjugates were obtained in the presence of PrP/R-250, inducing dramatically enhanced Raman signal. SERS responses enhanced with increasing amount of PrP and a linear equation of I SERS =6729.7+3091.2 c PrP was obtained in the range of 3.0–12.0×10 −9 M with the determination coefficient of 0.988. The proposed strategy is simple, rapid, and high specificity to probe protein–aptamer recognition in the solution. [ABSTRACT FROM AUTHOR]

Abstract: We have developed a simple, rapid and label-free sensor for the essential biological OH radicals based on the fluorescence quenching of DNA-templated Ag nanoclusters (DNA-Ag NCs). The OH radicals generated from the Fenton reagent attack and cleave the DNA template, which disturbs the microenvironments around Ag NCs, resulting in spontaneous aggregation due to the lack of stabilization and further the quenching of the Ag NCs fluorescence. These changes in fluorescence intensity allow sensing of OH radicals with good sensitivity and selectivity under optimal conditions. The sensor can be also applied for quantifying the radical scavenging action of antioxidants. Various characterizations including absorption spectra, fluorescence lifetimes, light scattering (LS) spectra, transmission electron microscopy (TEM), dark field light scattering imaging, and circular dichroism (CD) spectrometry have been employed to illustrate the proposed sensing mechanism. Further investigations demonstrate that the fluorescent probe could penetrate into intact cell membranes to selectively detect intracellular OH radicals induced by the phorbol myristate acetate (PMA) stimulation. These advantageous characteristics make the fluorescent DNA-Ag NCs potentially useful as a new candidate to monitor OH in broad biosystems. [Copyright &y& Elsevier]

Conventional methods for the detection of the sulfur mustard poisoning metabolic marker, thiodiglycol (TDG), require expensive instruments and reagents as well as professional operators. To address these problems, a novel test strip based on a molecularly imprinted sensitive membrane (MIM) was developed in this work for point-of-care (POC) detection of TDG. The TDG test strip was prepared conveniently by coating molecular imprinted polymers (MIPs) on a nitrocellulose membrane. When the sample contained TDG, the MIPs could specifically bind with TDG. A great number of AuNPs (AuNPs) could then be adsorbed on the test strip via the formation of an Au–S bond between TDG and AuNPs, giving the test strip the obvious red color of AuNPs. In the absence of TDG, the test strip exhibited much lighter color because it could not adsorb AuNPs. By monitoring the color change of the test strip, TDG could be detected from 1.0 ng/mL to 100.0 μg/mL with a detection limit of 0.23 ng/mL (3σ) under the optimal conditions (the molar ratio of TDG to MAA was 1:2; the eluent was chloroform; the elution time was 50 min; the reaction time between MIPs and TDG was 15 min; the adsorption time of AuNPs was 40 min; the temperature of the reaction system was 35 °C). This method has excellent selectivity and has been used to detect TDG in urine, showing great potential for POC detection of TDG in clinical samples. In this study, a novel molecular imprinting test strip based POCT method for the detection of thiodiglycol (TDG) by using gold nanoparticles (AuNPs) as colorimetric reporters was reported. [Display omitted] • A novel and stable molecularly imprinted test strip was developed for point-of-care (POC) detection of TDG. • By using AuNPs as colorimetric reporters, TDG could be detected through naked eyes straightforwardly. • This method has excellent selectivity and has been used to detect TDG in urine. [ABSTRACT FROM AUTHOR]