Naked eye instant reversible sensing of Cu(2+) and its in situ imaging in live brine shrimp Artemia

Mechanochemical Synthesis of Organic Dyes and Fluorophores

The syntheses of dyes and fluorophores have significant commercial importance. In recent years, mechanochemistry has emerged as a green and sustainable alternative for the synthesis of conventional dyes, new fluorophores, and also synthetic modification of known dyes for their use as chemosensors. The dyestuffs based on BODIPYs, rhodamine, fluorescein, perylenedimides, coumarins, benzothiazoles, etc. were synthesized or derivatized by grinding or milling. The synopsis aims to pay key attention to their synthesis and the applications as chemosensors will be briefly covered.

Estimation of bisulfate in edible plant foods, dog urine, and drugs: picomolar level detection and bio-imaging in living organisms

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.

Characterization of phenazine-1-carboxylic acid by Klebsiella sp. NP-C49 from the coral environment in Gulf of Kutch, India

Coral-associated microbes from Marine National Park (MNP), Gulf of Kutch (GoK), Gujarat, India, were screened for siderophore production. Maximum siderophore-producing isolate NP-C49 and its compound were identified and characterized. The isolate was identified as Klebsiella sp. through 16S rRNA genes sequencing (GenBank accession nos. KY412519 and MTCC 25160). Antibiotic susceptibility profile against 20 commercial antibiotics showed its more sensitivity compared to human pathogenic strain, i.e., Klebsiella pneumonia. The compound was identified as phenazine-1-carboxylic acid (PCA) using the multinuclear ID (¹H and ¹³C) and 2D (¹H-¹H COSY and ¹H-¹³C HETCOR) NMR along with high-resolution mass spectrometry. No significant difference in the bacterial growth in the presence of PCA, FeCl₃ and Fe(OH)₃ indicated involvement of factors other than PCA in bacterial growth. The study first reports the identification and characterization of PCA from Klebsiella sp. both from terrestrial and marine sources.

AIE active salicylaldehyde-based hydrazone: A novel single-molecule multianalyte (Al3+ or Cu2+) sensor in different solvents

A simple asymmetric hydrazone 1 based on salicylaldehyde was designed and prepared, and exhibited an evident aggregation-induced emission (AIE) at a long wavelength of 570 nm in aqueous medium. Probe 1 can selectively sense Al³⁺ in CH₃OH solution through the chelation-enhanced fluorescence mechanism and also recognize Cu²⁺ via fluorescence quenching in H₂O solution through the Cu²⁺-induced assembly of aggregates. In addition, the probe can be applied for detecting Cu²⁺ in biological samples.

Fabrication of a Cu(II)-Selective Electrode in the Polyvinyl Chloride Matrix Utilizing Mechanochemically Synthesized Rhodamine 6g as an Ionophore

A Cu(II)-selective electrode has been fabricated by utilizing a mechanochemically synthesized copper-specific ionophore "L" embedded in a poly(vinyl chloride) membrane. 2-Nitrophenyloctylether and sodium tetraphenylborate have been used as a plasticizer and as a solvent mediator, respectively, and found to be enhancing the sensitivity of the fabricated ion-selective electrode (ISE). A range of membranes (S1-S7) with varying compositions were casted and investigated in ISE. Results revealed an excellent Nernstian response of 29.38 ± 0.55 mV/dec for the ISE S6. The fabricated ISE operates well in the pH window 4.0-7.5, and the limit of detection was found to be 5 μM (0.3 ppm). Quick response time (15 s), long shelf-life, and selectivity (on the order of 10^-4 and 10^-5) over a number of interfering cations enabled S6 promising for real off laboratory sample analysis and can be employed to detect copper ion in various industrial as well as biological and environmental samples. To demonstrate the practical application of these ISE, the Cu concentration in the digested printed circuit board has been estimated using the standard calibration plot. The fabricated ISE has been regenerated through extracting copper by chelating with ethylenediaminetetraacetic acid.

A simple hydrazone as a multianalyte (Cu2+, Al3+, Zn2+) sensor at different pH values and the resultant Al3+ complex as a sensor for F−

A new colorimetric and fluorescence molecular chemosensor based on triazole hydrazone can be used as a multi-probe for selective detection of Al³⁺, Zn²⁺, and Cu²⁺ by monitoring changes in the absorption and fluorescence spectral patterns. Results show that Al³⁺ and Zn²⁺ ions can induce remarkable fluorescence enhancement at pH 6.0 and pH 10.0, respectively, while the addition of Cu²⁺ ions leads to a significant UV-visible absorption enhancement in the visible range at pH 6.0. In addition, the resultant Al³⁺ complex could act as an ‘on–off’ fluorescence sensor for F⁻. The fluorescence sensor was also used to monitor intracellular Al³⁺, Zn²⁺, and F⁻ in Hela cells.

A fluorescent probe for Al³⁺ and Zn²⁺ was synthesised, and the resultant Al³⁺-complex was used for the detection of F⁻.

Siderophore coated magnetic iron nanoparticles: Rational designing of water soluble nanobiosensor for visualizing Al3+ in live organism

This article aims to establish the judicious use of iron-binding chemistry of microbial chelators in order to functionalize the surface of iron nanoparticles to develop non-toxic nanobiosensor. Anchoring a simple siderophore 2,3-dihydroxybenzoylglycine (H₃L), which bears catechol and carboxyl functionalities in tandem, on to the surface of Fe₃O₄ nanoparticles has developed a unique nanobiosensor HL-FeNPs which showed highly selective and sensitive detection of Al³⁺ in 100% water at physiological pH. The biosensor HL-FeNPs, with 20nM limit of detection, behaves reversibly and instantly. In-vivo bio-imaging in live brine shrimp Artemia confirmed that HL-FeNPs could be used as fluorescent biomarker for Al³⁺ in live whole organisms. Magnetic nature of the nanosensor enabled HL-FeNPs to remove excess Al³⁺ by using external magnet. To our knowledge, the possibility of microbial chelator in the practical development of Al³⁺ selective nanobiosensor is unprecedented.

Reporting a new siderophore based Ca2+ selective chemosensor that works as a staining agent in the live organism Artemia

A new acyclic chemosensor bearing a siderophore linked to a rhodamine 6G fluorophore showed highly selective detection of Ca²⁺ ions in 100% aqueous solution at pH 7.4. The probe showed bio-imaging applicability in the live animal Artemia.