A cost-effective Z-folding controlled liquid handling microfluidic paper analysis device for pathogen detection via ATP quantification.

A cost-effective microfluidic paper analysis device (µPAD) was developed with a special Z-folding design for controlling the fluidic flowing and substrate transportation. This presented µPAD can be easily fabricated through wax printing by using a solid ink printer which deposits wax onto the surface of a chromatographic paper, and then baked on a hotplate by penetrating the molten wax into the paper to create a hydrophobic barrier. After µPAD fabrication, liquid control and substrate transportation can be easily carried out by twice folding the µPAD following Z shape. The Z folding made two separated reagent holding zone connected while the detection reaction occurred with the connection. In this paper, a pathogens detection indicated by ATP quantification was took as a proof-in-principle application of using this presented µPAD, the limit of detection (LOD) was 1 µM for ATP detection and 2.6×10(7) CFU/mL for Salmonella live cell detection, which showed a great potential for Point-of-Care Testing (POCT) applications.

DNA-hosted Hoechst dyes: application for label-free fluorescent monitoring of endonuclease activity and inhibition.

A simple and facile approach was developed for monitoring EcoRI endonuclease activity and inhibition, in which a hairpin-like DNA containing restriction cutting site for EcoRI endonuclease acts as the sensing element and Hoechst dyes as the signal indicator in a label-free format.

A ratiometric fluorescent probe for sensitive, selective and reversible detection of copper (II) based on riboflavin-stabilized gold nanoclusters.

Most of the copper (II) fluorescent probes are based on the measurement of fluorescence at a single wavelength, which may be influenced by variations in the sample environment. To the end, the ratiometric fluorescent measurement, which involves the simultaneous measurement of two fluorescence signals at different wavelengths followed by calculation of their intensity ratio, can effectively eliminate the adverse effects on fluorescence signals and give greater precision to the data analysis relative to single-channel detection. In this work, we prepared novel luminescent gold nanoclusters (AuNCs) utilizing vitamin B2 (riboflavin) as stabilizer by a simple, rapid and one-pot green (low-toxicity materials use) procedure. The as-prepared riboflavin-AuNCs (Ri-AuNCs) solution can be luminescent exhibiting two fluorescence emission peaks at 530 nm and around 840 nm with excitation at 375 nm, however, in the presence of Cu(2+), the fluorescence of the Ri-AuNCs was found to be quenched at around 840 nm and enhanced at 530 nm by Cu(2+). The resultant ratiometric fluorescent response can provide a novel sensory probe for the determination of Cu(2+). The present probe had excellent selectivity in the presence of several cations. The probe revealed a detection limit of 0.9 µM of Cu(2+). Moreover, our proposed probe can reversibly switch between the "on" and "off" states through the addition of Cu(2+) and EDTA, which is reusable in practical application. Results and method reported here provide a unique strategy for performance of ratiometric assays demonstrated with a AuNCs-based fluorescent probe, which expands the application of AuNCs.

A label-free fluorescent molecular beacon based on DNA-templated silver nanoclusters for detection of adenosine and adenosine deaminase.

A simple and reliable fluorescent molecular beacon is developed utilizing DNA-templated silver nanoclusters as a signal indicator and adenosine triphosphate (ATP) and adenosine deaminase as mechanical activators.