The oxidative dehydrogenation of a coumarinyl scaffold with copper ion and metal ion detection in human liver cancer cells (HepG2)

A near-infrared fluorescent probe for imaging of bisulfite in living animals and its application in food samples

Bisulfite (HSO₃^-) has been widely used as an antioxidant, enzyme inhibitor and antimicrobial agent in foodstuffs, pharmaceutical and beverages industries. It is also a signaling molecular in the cardiovascular and cerebrovascular systems. Nevertheless, a high level of HSO₃^- can cause allergic reactions and asthmatic attacks. Accordingly, the monitoring of HSO₃^- levels possesses momentous significance from the perspectives of biological technology and food security supervision. Herein, a near-infrared fluorescent probe LJ is rationally constructed for sensing HSO₃^-. The fluorescence quenching recognition mechanism was realized by the addition reaction of electron-deficient CC bond in probe LJ and HSO₃^-. Probe LJ revealed multifarious preponderances such as longer wavelength emission (710 nm), low cytotoxicity, larger Stokes shift (215 nm), better selectivity, higher sensitivity (72 nM) and short response time (50 s). Encouragingly, probe LJ can detect HSO₃^- in living zebrafish and mice in vivo by fluorescence imaging techniques. In the meantime, probe LJ was also successfully employed to semi-quantitatively detect HSO₃^- in real foodstuff samples and water samples by the "naked-eye" colorimetry without the help of any special instruments. More importantly, quantitative detection of HSO₃^- in practical food samples was achieved through a smartphone application software. Consequently, probe LJ is expected to provide an effective and convenient way for the detection and monitoring of HSO₃^- in organisms and for food safety detection, which has tremendous application potential.

A highly emissive Zn(II)-pyridyl-benzimidazolyl-phenolato-based chemosensor: detection of H2PO4-via "use" and "throw" device fabrication

2-Ethoxy-6-[1-(phenyl-pyridin-2-yl-methyl)-1H-benzoimidazol-2-yl]-phenol (HL) selectively serves as a sensitive 'turn on' Zn²⁺ sensor in 9 : 1 (v/v) DMSO/H₂O (HEPES buffer, pH = 7.4) medium in the presence of sixteen other cations at the limit of detection (LOD) of 3.2 nM. The strong blue emission of the complex, {[Zn(L¹)OAc]} (HL¹ = benzimidazolyl ring-opening structure of HL) (λ_em, 461 nm), is quenched by H₂PO₄^- in the presence of eighteen other anions and the LOD is 0.238 μM. The emission of the complex is due to restricted intramolecular rotation (RIR) followed by chelation-enhanced fluorescence (CHEF). The quenching of the emission of [Zn(L¹)OAc] by H₂PO₄^- (in the presence of other P^Vs (inorganic and biological) as well as additional anions) is due to the 'turn off' fluorescence via the demetallation and release of the nonfluorescent ligand, HL, and [Zn(H₂PO₄)]⁺. An INHIBIT logic gate memory circuit of the probe HL was devised with Zn²⁺ and H₂PO₄^- as two consecutive inputs. The percentage of H₂PO₄^- recovery was excellent and was obtained from distilled, tap, and drinking water sources. The bright blue emission of [Zn(L¹)OAc] further triggered the fabrication of ready-made portable thin films of the Zn-complex, which executed a cost-effective 'on-site' solid-state contact mode detection of H₂PO₄^- with selectivity at the picogram level (10.97 pg cm^-2) by monitoring the intensities of quenched spots under UV light upon varying the analyte concentration from 10^-8 to 10^-3 M. Finally, taking advantage of reversible fluorescence switching, a simple and definite ion-responsive security feature was successfully embedded into a "use" and "throw" solution-coated paper strip of the Zn(II)-pyridyl-benzimidazolyl-phenolato-based chemosensor, which efficiently detected H₂PO₄^- in water by a successive 'ON-OFF' fluorescence switching-driven security activity without any exhaustion of the emission phenomenon.

A Novel Fluorescence Probe for the Reversible Detection of Bisulfite and Hydrogen Peroxide Pair in Vitro and in Vivo

The detection of changes in the reactive oxygen species (ROS)/reactive sulfur species (RSS) couple is important for studying the cellular redox state. Herein, we developed a 1,8-naphthalimide-based fluorescence probe (NI) for the reversible detection of bisulfite (HSO₃ ^- ) and hydrogen peroxide (H₂ O₂ ) in vitro and in vivo. NI has been designed with a reactive ethylene unit which specifically reacts with HSO₃ ^- by a Michael addition reaction mechanism, resulting in the quenching of yellow fluorescence at 580 nm and the appearing of green fluorescence at 510 nm upon excitation at 500 nm and 430 nm, respectively. The addition product (NI-HSO₃ ) could be specifically oxidized to form the original C=C bond of NI, recovering the fluorescence emission and color. The detection limits of NI for HSO₃ ^- and NI-HSO₃ for H₂ O₂ were calculated to be 2.05 μM and 4.23 μM, respectively. The reversible fluorescence response of NI towards HSO₃ ^- /H₂ O₂ couple can be repeated for at least five times. NI is reliable at a broad pH range (pH 3.0-11.5) and features outstanding selectivity, which enabled its practical applications in biological and food samples. Monitoring the reversible and dynamic inter-conversion between HSO₃ ^- and H₂ O₂ in vitro and in vivo has been verified by fluorescence imaging in live HeLa cells, adult zebrafish and nude mice. Moreover, NI has been successfully applied to detect of HSO₃ ^- levels in food samples.

Solid-State Emissive Metallo-Supramolecular Assemblies of Quinoline-Based Acyl Hydrazone

Development of fluorescence-based sensory materials for metal elements is currently in the mainstream of research due to the simplicity and usability of fluorescence as a method of detection. Herein, we report a novel "bis"-quinoline-based acyl hydrazone-named bQH that could be synthesized by a facile, low-cost method through simple condensation of hydrazide with an aldehyde. This acyl hydrazone showed emissive properties through Zn selective binding, especially in its solid-state, as shown by experiments such as UV-Vis, photoluminescence (PL), nuclear magnetic resonance (NMR), and inductively-coupled plasma-optical emission spectroscopies (ICP-OES), and energy-dispersive X-ray spectroscopy (EDS) mapping. The binding modes in which bQH coordinates to Zn2+ was proved to consist of two modes, 1:1 and 1:2 (bQH:Zn2+), where the binding mode was controlled by the Zn2+ ion content. Under the 1:1 binding mode, bQH-Zn2+ complexes formed a polymeric array through the metallo-supramolecular assembly. The resulting bQH-Zn2+ complex maintained its fluorescence in solid-state and exhibited excellent fluorescence intensity as compared to the previously reported quinoline-based acyl hydrazone derivative (mQH).