A novel copper(Ⅱ) complex-based fluorescence probe for nitric oxide detecting and imaging

Ex Tenebris Lux: Illuminating Reactive Oxygen and Nitrogen Species with Small Molecule Probes

Reactive oxygen and nitrogen species are small reactive molecules derived from elements in the air─oxygen and nitrogen. They are produced in biological systems to mediate fundamental aspects of cellular signaling but must be very tightly balanced to prevent indiscriminate damage to biological molecules. Small molecule probes can transmute the specific nature of each reactive oxygen and nitrogen species into an observable luminescent signal (or even an acoustic wave) to offer sensitive and selective imaging in living cells and whole animals. This review focuses specifically on small molecule probes for superoxide, hydrogen peroxide, hypochlorite, nitric oxide, and peroxynitrite that provide a luminescent or photoacoustic signal. Important background information on general photophysical phenomena, common probe designs, mechanisms, and imaging modalities will be provided, and then, probes for each analyte will be thoroughly evaluated. A discussion of the successes of the field will be presented, followed by recommendations for improvement and a future outlook of emerging trends. Our objectives are to provide an informative, useful, and thorough field guide to small molecule probes for reactive oxygen and nitrogen species as well as important context to compare the ecosystem of chemistries and molecular scaffolds that has manifested within the field.

Optical fluorescent sensor based on perovskite QDs for nitric oxide gas detection

In this paper, a new, to the best of our knowledge, optical fluorescent sensor for the sensing of nitric oxide (NO) gas is developed. The optical NO sensor based on C s P b B r ₃ perovskite quantum dots (PQDs) is coated on the surface of filter paper. The C s P b B r ₃ PQD sensing material can be excited with a UV LED of a central wavelength at 380 nm, and the optical sensor has been tested in regard to monitoring different NO concentrations from 0-1000 ppm. The sensitivity of the optical NO sensor is represented in terms of the ratio I _N2/I _{1000p p m N O} , where I _N2 and I _{1000p p m N O} represent the detected fluorescence intensities in pure nitrogen and 1000 ppm NO environments, respectively. The experimental results show that the optical NO sensor has a sensitivity of 6. In addition, the response time was 26 s when switching from pure nitrogen to 1000 ppm NO and 117 s when switching from 1000 ppm NO to pure nitrogen. Finally, the optical sensor may open a new approach for the sensing of the NO concentration in the harsh reacting environmental applications.

Gas phase microdialysis and chemiluminescence detection: A small, fast, selective, and sensitive method to monitor aqueous nitric oxide

A method using a gas-phase microdialysis probe interfaced with a modified commercially available nitric oxide (NO) detector is shown to selectively measure aqueous NO at low μM levels with high selectivity. The detector measures chemiluminescence resulting from the gas-phase reaction of NO with ozone. The microdialysis probe is small enough (3 mm × 200 μm) to be used in vivo. Because the processes of extraction across the microdialysis membrane and transport from the probe to the detector are both very fast, the response time is shorter than 5 s. The method was verified using two different quantifiable sources of NO: nitrite and methylamine hexamethylene methylamine (MAHMA) NONOates. To demonstrate ruggedness and to show the impact of matrix on NO generation, the method was used to measure NO in a cell culture matrix. The continuous extraction, fast response time, and rugged nature make the method useful for monitoring NO in biological applications. Our results also show that predicting NO concentration for in vitro experiments based on NONOate concentration may be a poor assumption due to the pH dependence of NO formation and the rapid decline in NO concentration.

Synthesis of New Quinoline-Conjugated Calixarene as a Fluorescent Sensor for Selective Determination of Cu2+ Ion

A novel quinoline-functionalized calix [4] arene derivative (Quin-Calix) has been successfully synthesized at partial cone conformation and duly characterized by using FTIR, ¹H-NMR, ¹³C-NMR, ESI-MS and elemental analysis techniques. Moreover, the cation-binding property of the calix [4] arene derivative (Quin-Calix) has been investigated towards Cu²⁺, Ba²⁺, Cd²⁺, Co²⁺, Ni²⁺, Zn²⁺ and Fe³⁺ ions, and the recognition event monitored by UV-Vis absorption and fluorescence studies. The results indicated that Quin-Calix displays a remarkable affinity and selectivity only for Cu²⁺ ion. The binding constant and stoichiometry of the complex formed between Quin-Calix and Cu²⁺ ion have been also calculated from the fluorescence data. In addition, Stern-Vohmer equation has been used to elucidate the mechanism of quenching.

Application of nanodiamonds in Cu(ii)-based rhodamine B probes for NO detection and cell imaging

A nanodiamond-conjugated rhodamine fluorescent sensor for Cu(ii) which could then be developed as an excellent NO selective fluorescent particle.

A novel copper(II) complex as a nitric oxide turn-on fluorosensor: intracellular applications and DFT calculation

We report, herein, the development of an easily synthesizable novel dansyl-based turn-on NO sensor L2. The UV-Vis titration data of L2 with Cu(2+) display a gradual increase in absorbance at 418 nm with [Cu(2+)], which were analyzed by using a non-linear least-squares computer-fit program yielding K = (1.16 ± 0.36) × 10(6) M(-1) and n = (1.28 ± 0.03) indicating a 1 : 1 complexation. The ground state geometries of L2 as well as its complex [Cu(L2)Cl](+) (1) were optimized by DFT calculations which showed that in complex 1 the central metal ion is in distorted tetrahedral geometry with bond distances very close to those found in analogous Cu(2+) complexes. The fluorescence of L2 was dramatically quenched (∼60-fold) through complexation with paramagnetic Cu(2+) to form [Cu(L2)Cl](+) in MeCN-H2O (9 : 1, v/v) at pH 7.2 in HEPES buffer, which on further treatment with Angeli's salt (Na2N2O3) restores its fluorescence property by ∼15-fold due to the reduction of Cu(2+) to Cu(+) by NO generated in solution from Na2N2O3. The lifetime measurements displayed a substantial decrease in the lifetime of free ligand L2 (τ0 = 12 ns) on complexation with Cu(2+) (τ0 = 2.1 ns). The detection limit of NO calculated by the 3σ method gives a value of 1.6 nM. The NO induced fluorescence enhancement of [Cu(II)(L2)Cl](+) was due to the reduction of [Cu(II)(L2)Cl](+) (1) to [Cu(I)(L2)](+) (2) and is supported by the disappearance of the d-d transition band at 850 nm as well as the X-band EPR signal of 1. The selective "turn on" fluorogenic behavior of L2 was examined on HeLa cells of human cervical cancer origin by fluorescence microscopy which showed very intense intracellular fluorescence that was strongly suppressed by the addition of Cu(2+) but it regains its fluorescence property on further incubation with Angeli's salt (Na2N2O3). The existence of [Cu(II)(L2)Cl](+) and [Cu(I)(L2)](+) in solution was confirmed by ESI-MS(+) (m/z) analysis. The effect of different biologically relevant cations and anions on the fluorescence property of L2 indicates that it was only the [Cu(II)(L2)Cl](+) which displayed high selectivity for NO, indicating its suitability for intracellular application without much worry about its cytotoxicity in a specified dose.