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A newly designed quantum dots and manganese dioxide nanosheets nanocomposite-based fluorescence lateral flow biosensor was developed for rapid detection of glutathione (GSH). In this biosensing system, nanocomposites of biotinylated quantum dots (Biotin-QDs) and MnO 2 nanosheets were first fixed on the conjugation pad of the test strip. The addition of GSH could trigger the decomposition of nanocomposites by digesting MnO 2 nanosheets and consequently release Biotin-QDs. Under the capillary effect, the free Biotin-QDs would continue to move forward and be captured by streptavidin (SA) on the test line due to the specific binding between biotin and SA. Thereafter, an obvious fluorescent enhancement can be observed on the test line with a portable strip reader as well as naked eyes under irradiation by a 365 nm handheld ultraviolet lamps, which was used successfully for the quantitative detection of GSH with a short assay time of 20 min. Furthermore, this biosensor was utilized for GSH detection in diluted HeLa cells extracts (1%) samples with satisfactory results, which can meet low concentration detection for GSH with a good linear relationship in the range from 0.05 to 1.2 mM. Holding the advantages such as simple, convenient, rapid and cost effective, this developed fluorescence lateral flow biosensor has a great potential to be used for GSH detection in point of care diagnosis. [ABSTRACT FROM AUTHOR]

Glutathione (GSH) is the most abundant biothiol in cells and plays key roles in biological processes. Therefore, it is vitally important to detect GSH in biological samples. In this work, by using a novel quantum dots-based “off-on” fluorescent lateral flow test strip (LFTS), the authors describe a rapid and sensitive biosensor for point-of-care testing of GSH. In this design, bovine serum albumin (BSA) functionalized quantum dots (QDs) are chosen as signal reporter and modified on the test line of the LFTS. When Ag + binds to the surface of QDs, the fluorescence of QDs can be quenched efficiently owing to the electron transfer from QDs to Ag + . In the presence of GSH, due to the much stronger affinity between Ag + and GSH, Ag + prefers to react with GSH to form Ag + -S bond. Consequently, the fluorescence of QDs is restored and GSH quantification is realized successfully. Under the optimal conditions, a good linear relationship from 0.1 μM to 15 μM with a detection limit of 25 nM was obtained, and the whole process can be accomplished quickly within 10 min. In addition, this proposed biosensor showed acceptable recovery (98.4%–102.2%) for the detection of GSH in Hela cells extract samples. [ABSTRACT FROM AUTHOR]

In this work, cobalt oxyhydroxide nanoflakes (CoOOH nanoflakes) were reported to possess a high oxidizability toward TMB for the first time and based on which we have developed a new strategy for qualitative and quantitative detection of ascorbic acid (AA). In our design, CoOOH nanoflakes can directly oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to oxTMB with an obvious blue color emerging, and AA can selectively inhibit the oxidation of TMB to oxTMB by resolving CoOOH nanoflakes to Co 2+ , resulting in a decrease in the absorbance of oxTMB and bleaching of blue color. As such, the concentration of AA could be identified very easily by UV–vis spectroscopy and bare eyes. Under optimal conditions, this sensing platform showed a highly sensitive response to AA with a detection limit of 142 nM and a short assay time of 5 min. This assay was also successfully used to quantify AA in human serum samples and practical food samples. Importantly, using this fabricated sensing strategy, we have further developed a paper-based strip sensor for AA detection with satisfactory results, showing its great potential for point of care applications. [ABSTRACT FROM AUTHOR]