Detecting Pb2+ in aqueous environment and live cells by amphiphilic pillar[5]arene-assembled supramolecular sensor based on host-guest charge transfer mechanism.

Water-soluble fluorescent chemosensors for lead ion are highly desirable in environmental detection and bioimagery. Based on a water-soluble pillar[5]arene WP5 and imidazolium terminal functionalized 2,2'-bibenzimidazole derivative BIHB, we report a host-guest charge transfer assembly BIHB-2WP5 for sensitive and selective detection of Pb2+ in pure aqueous media. As a result of its high electron-rich cavity, WP5 can bind electron-deficiency guest BIHB with various host/guest stoichiometry to easily tune the microtopography of assembly from nanoparticle to nanocube. In view of the good biocompatibility and sensitivity, the supramolecular assembly BIHB-2WP5 was used as a fluorescent probe for the detection of Pb2+ in living cells and a smartphone Pb2+ detection device was constructed for the in situ test.

On paper synthesis of metal-organic framework as a chemiluminescence enhancer for estimating the total phenolic content of food samples using a smartphone readout.

Herein, a novel paper-based chemiluminescence (CL) assay is reported using a smartphone readout for on-site and reliable analytical applications. The CL system was based on the high-performance improving effect of cobalt-imidazole metal-organic framework (CoMOF) on luminol-hydrogen peroxide (H2O2) CL emission. The CoMOF was grown on paper and used as a support for the CL reaction, which led to an intense CL emission and good reproducibility. More importantly, the stability of luminol, as the CL reagent, was greatly improved in the presence of CoMOF. This high stability, along with the high-yield CL emission, makes the device highly suitable for commercialization. Furthermore, using a smartphone as the detector for the developed device made the process easier and more accessible for public usage. In this work, the new paper-based CL smartphone device was used for the detection of the total phenolic content of food samples. Phenolic compounds (PC) are hydroxyl radical scavengers that can effectively quench the CL emission of the luminol-H2O2-CoMOF system. After optimizing the reaction conditions, the system could detect PC at the µg mL-1 level. Detection limits of 0.12, 0.28, 0.46, 0.85, and 1.23 µg mL-1 were obtained for gallic acid, quercetin, catechin, kaempferol, and caffeic acid, respectively. This work is the first report on the practical application of smartphone CL assays for the estimation of PC. The proposed assay is an easy-to-use, low-cost, portable, and suitable assay for on-site screening purposes.

Colorimetric copper ion sensing in solution phase and on paper substrate based on catalytic decomposition of S-nitrosothiol.

A S-nitrosothiol (RSNO) is used for highly selective and sensitive copper ion sensing for the first time. Cu(II) in the sample is reduced to Cu(I) by a low amount of thiols generated from hydrolysis of RSNO molecules or added thiols such as l-glutathione or l-cysteine. Cu(I) is able to trigger cleavage of the SNO bond, which converts colored RSNOs to colorless products. The dark green S-nitroso-N-acetylpenicillamine is used as an exemplary RSNO in this report. In the spectrophotometric test, the detection limit toward Cu(II) is 0.23 µM without added thiol reductants, and 0.08 and 0.06 µM in the presence of l-glutathione and l-cysteine, respectively. Furthermore, we prepared fully inkjet printed paper-based sensors by deposition of all reaction reagents and buffers on the same piece of cellulose paper. A smartphone equipped with a color analysis app enables quantification of the color change of the paper-based Cu(II) sensors. In this method, a detection limit of 1.2 µM and a linear range of 0-10 µM were obtained. Finally, we successfully applied this instrumentation-free and reagent-free senor for Cu(II) analysis in real drinking water and river water samples.

Biochemical-immunological hybrid biosensor based on two-dimensional chromatography for on-site sepsis diagnosis.

A hybrid-biosensor system that can simultaneously fulfill the immunoassay for protein markers (e.g., C-reactive protein (CRP) and procalcitonin (PCT)) and the enzyme assay for metabolic substances (e.g., lactate) in the same sepsis-based sample has been devised. Such a challenge was pursued through the installation of an enzyme-reaction zone on the signal pad of the typical immuno-strip for the rapid two-dimensional (2-D)-chromatography test. To minimize the mutual interference in the hybrid assays, a pre-determined membrane site was etched in a pattern and mounted with a biochemical-reaction pad, thereby allowing a loaded sample to enter and then stay in the pad for a colored-signal production over the course of an immunoassay. By employing such a constructed system, a serum sample was analyzed according to the vertical direction flowing along the strip, which supplied lactate to the biochemical-reaction zone and then protein markers to the immunological-binding area that was pre-coated with capture antibodies. Thereafter, the enzyme-signal tracers for the immunoassay and the substrate solution were sequentially furnished using a horizontal path for the tracing of the immune complexes that were formed with CRP or PCT. The color signal that was produced from each assay was detected at a pre-determined time and quantified on a smartphone-based detector. Under the optimal conditions, the dynamic ranges for the analytes covered the respective clinical ranges, and the total coefficient of variation was between 8.6% and 13.3%. The hybrid biosensor further showed a high correlation (R2 > 0.95) with the reference systems for the target markers.