Search

Lab-on-a-paper-based devices are promising alternatives to the existing arduous techniques for point-of-need monitoring. The present work reports an instant and facile method to produce a microfluidic paper-based analytical device (μPAD). The fabricated μPAD has been used to detect hypochlorite (OCl−) by incorporating newly synthesized chromo-fluorogenic ratiometric probes 1 and 2 into the sample reception zone. The probes showed high selectivity and fast response (<10 s) toward OCl− with an excellent linear relationship in the concentration range of 0–100 μM. The concentration-dependent fluorometric change driven by the reaction of 1@μPAD with OCl− has been monitored using gel-doc imaging systems, which is unprecedented. Digitizing the intensity of the colour solution with different mathematical models of colour has developed a straightforward method for monitoring OCl− without any interference from its competitors. 1@μPAD can detect OCl− at ∼10 times lower than the WHO recommended limit. The detection limit of 1@μPAD via a digital camera-based fluorescence technique was found to be better over digital camera-based cuvette assays. Therefore, 1@μPAD has been successfully utilized to monitor OCl− in actual environmental water samples with portability, ease of use, and sensitivity. The analytical RSD was found to be ≤3% based on fluorimetric detection using 1@μPAD. The chemodosimetric reaction between OCl− and the probe was evidenced by UV-vis and fluorescence spectroscopy, 1H NMR, and ESI-MS. The rapid response time, biocompatibility, low cytotoxicity, 100% aqueous solubility, ratiometric feature, and exclusive OCl− selectivity over other competitive ROS/RNS successfully lead to the application of the probes for bioimaging of exogenous as well as endogenous OCl− in normal cells (HEK293) and cancerous cells (HeLa). [ABSTRACT FROM AUTHOR]

The development of receptors that can detect as well as treat cyanide ions in aqueous samples is indispensable for environmental protection. Herein, we present the bulk solvent-free and instant green synthesis of a series of turn-on fluorimetric probes that can specifically detect the deadly poison cyanide among various anions and metal ions in water. Selective recognition of cyanide by the mechanosynthesized compounds is even observable by the naked eyes, which remained unaffected in the presence of various challenging species. NMR spectroscopic investigation supports the chemodosimetric sensing of cyanide by the receptors. A remarkable 55–83 fold fluorescence enhancement by the probes enabled us to reach a limit of detection (LOD) in the range of 8–26 ppb, well below the permissible limit of cyanide in drinking water. Being minuscule soluble in water, cyanide treatment studies with the ionophores showed greater than 99% reduction in the free cyanide concentration after three consecutive cycles of operation. Furthermore, the compounds can be used as sensitive probes for the estimation of cyanide in human blood serum in physiological conditions. Overall, the results presented in this article will certainly find great use in the area of cyanide pollution with regard to simultaneous sensing and treatment of free cyanide, which is heretofore unprecedented. [ABSTRACT FROM AUTHOR]

In order to explore the properties of any species in solution, the actual, i.e. equilibrium concentration of the free species should be taken into account. Researchers have not paid attention to the deprotonation equilibrium between HSO4− and SO42− while probing bisulfate ion. In this study, we have addressed this concern and developed two zwitterions, CG (coumarin-integrated glycine) and CA (coumarin-integrated alanine), for the selective detection of HSO4− at a picomolar level (50 to 325 pM) with very high binding affinity (∼108 M−1) in pure water at physiological pH. The principle of HSO4− recognition was established via UV-vis and fluorescence techniques. DFT calculations suggested that the H-bonding interactions between the probes and HSO4− are the driving force for this unforeseen selectivity. The membrane penetration ability and nontoxicity of CG/CA enable them to function as staining agents in living brine shrimps and bacteria. The use of these probes for the estimation of HSO4− in various day-to-day edible foods and drugs along with urine samples is unprecedented. The significance and novelty of this study lies in the application and development of assays for estimating bisulfate in several real-world samples that are predominantly aqueous in nature, which are the first of their kind. [ABSTRACT FROM AUTHOR]

A Ca2+-specific chemosensor involving acyclic non-ether and non-carboxylato-type metal chelating ligands is rare. The tetradentate OONO artificial receptor, HL, possessing a sulfur-containing intermediate siderophore aeruginic acid, tethered to a rhodamine 6G based signalling unit in a single molecule has been synthesized. The fluoroionophore required excitation in the visible wavelength (510 nm) and showed highly selective and sensitive detection of Ca2+ ions in 100% water solution in HEPES buffer at physiological pH (7.4). The probe HL, with LOD as low as 70 nM, behaves reversibly and showed nearly 17-fold enhanced selectivity for Ca2+ over other cell abundant alkali and alkaline metal ions such as Na+, K+, Li+, and Mg2+ without any intervention. Job's plot, 1H NMR titration and ESI-MS data provided corroborative evidence in support of 1 : 1 association between HL and Ca2+. From a wide range of transition and heavy metal ions series, HL also binds Cu2+. However, the use of l-cysteine removes the interference from Cu2+ and results in highly selective detection specificity of HL for Ca2+. As a reversible “off–on–off” fluorescent chemosensor, it is possible to detect Ca2+ at as low as 5 μM in the midgut region of the gastrointestinal tract of the live animal Artemia, a brine shrimp. [ABSTRACT FROM AUTHOR]

A Cu2+-specific colorimetric reversible fluorescent receptor HL was designed and synthesized which showed a naked eye observable colour change from colourless to pink on addition of an aqueous buffer (pH 7.4) solution of 30 ppb Cu2+. Short response time (≤5 s) and low detection limit (nearly 3 ppb) make HL suitable as a reliable “dip-in” open eye sensor for Cu2+. Bio-imaging application in live brine shrimp Artemia enabled HL to detect Cu2+ at as low as 10 ppb exposure. [ABSTRACT FROM AUTHOR]