An amphiphilic dansyl based multianalyte sensor for the detection of Hg2+, PPi, and TNP: A three-in-one chemical sensor.

A fluorescent dansyl-based amphiphilic probe, 5-(dimethylamino)-N-hexadecylnaphthalene-1-sulfonamide (DLC), was synthesized and characterized to detect multiple analytes at different sensing environments. In acetonitrile, DLC detects nitro explosives such as trinitrophenol (TNP) and 2,4-dinitrophenol (2,4-DNP) by an emission "on-off" response method, and the detection limits (LOD) were estimated to be as low as 4.3 µM and 17.4 µM, respectively. Amphiphilic long chains of the probe were embedded into lipid bilayers to form nanoscale vesicles DLC.Ves. Nanovesicular probe DLC.Ves was found to be highly selective for Hg2+ among other metal ions and for pyrophosphate (PPi) ions among various anions. DLC.Ves could detect Hg2+ with a turn "on-off" emission and PPi with ratiometric change in emission at 525 nm. It is proposed that DLC.Ves could detect Hg2+ via the Hg2+-induced aggregation quenching mechanism and PPi through the Hydrogen bonding. The LODs are estimated as 6.41 µM and 70.9 µM for Hg2+ and PPi, respectively. 1H NMR, SEM, and fluorescence lifetime measurements confirmed the binding mechanism. Thus, it is believed that the simple fluorescent probe DLC could be a prominent sensor to detect multiple analytes depending on the sensing medium.

Fluorescent nanoprobes for the sensing of gasotransmitters hydrogen sulfide (H2S), nitric oxide (NO) and carbon monoxide (CO).

Fluorescent nanomaterials as sensing probes have experienced immense growth in recent years due to the intrinsic optical and physicochemical properties, high sensitivity, specificity, targeting ability, and suitability for medicinal applications. The fluorescent detection of gaseous signaling molecules, such as Hydrogen sulfide (H2S), nitric oxide (NO) and carbon monoxide (CO) are very important due to their potential therapeutic application. This review intends to provide the recent progress in the detection of H2S, CO and NO via fluorescent based nano probes. These probes work based on different mechanisms such as fluorescence enhancement and quenching, also defined as "turn-on" and "turn-off" responses respectively. It could be achieved through PET, FRET or ratiometric methods. In this article, we have discussed about a variety of fluorescent nanoprobes of QDS, CDs, AuNPs and UCNPS, working on the fluorescent sensing mechanisms and applicable for the detection of H2S, CO and NO in biological and environmental samples. Methods used for the detection, structural features of nanomaterials, type of fluorescence response observed, fluorescence sensing mechanism and their sensitivity are highlighted.

Multi analyte sensing of amphiphilic tridentate bis(benzimidazolyl)pyridine incorporated in liposomes and potential application in enzyme assay.

A liposome based nanosensor Lipo-1 for efficient detection of copper, cyanide (CN-) and ATP in a pure aqueous medium has been described. Lipo-1 shows a fluorescence ON-OFF response with copper. However, Lipo-1.Cu (Lipo-1 and copper ensemble) was used for the OFF-ON detection of ATP with nM and CN- with µM detection levels, lower than the WHO permissible level for safe drinking. Lipo-1 has better and enhanced binding properties over the counter organic amphiphilic compound Bzimpy-LC, which is not soluble in water. The significant changes in the emission spectra in the presence of Cu2+, CN- and ATP ions, as variable inputs, are used to construct INHIBIT and OR logic operations in a nano-scale environment. The fluorescent detection of CN- ions with Lipo-1.Cu was used to develop an enzyme assay for ß-glucosidase using amygdalin as the substrate. ß-Glucosidase enzymatic activity was monitored by the emission OFF-ON signal of the probe Lipo-1.Cu by CN- detection. This approach could be an efficient method for developing a fluorescence-based ß-glucosidase enzyme assay. A switch ON luminescence response, low detection limit, fast response, 100% aqueous solution, biocompatibility, multi-analyte detection, and improved sensitivity and selectivity of Bzimpy-LC in lipid bilayer membranes are the main features of the nanoprobe Lipo-1. These properties give it a clear advantage for analytical applications.

Sensing and Bioimaging of the Gaseous Signaling Molecule Hydrogen Sulfide by Near-Infrared Fluorescent Probes.

A fluorescent probe for the monitoring of H2S levels in living cells and organisms is highly desirable. In this regard, near-infrared (NIR) fluorescent probes have emerged as a promising tool. NIR-I and NIR-II probes have many significant advantages; for instance, NIR light penetrates deeper into tissue than light at visible wavelengths, and it causes less photodamage during biosample analysis and less autofluorescence, enabling higher signal-to-background ratios. Therefore, it is expected that fluorescent probes having emission in the NIR region are more suitable for in vivo imaging. Consequently, a considerable increase in reports of new H2S-responsive NIR fluorescent probes appeared in the literature. This review highlights the advances made in developing new NIR fluorescent probes aimed at the sensitive and selective detection of H2S in biological samples. Their applications in real-time monitoring of H2S in cells and in vivo for bioimaging of living cells/animals are emphasized. The selection of suitable dyes for designing NIR fluorescent probes, along with the principles and mechanisms involved for the sensing of H2S in the NIR region, are described. The discussions are focused on small-molecule and nanomaterials-based NIR probes.