Search

Four novel compounds (S-DCM-1O, S-DCM-2O, S-DCM-3O, and S-DCM-4O) based on sulfur-substituted dicyanomethylene-4H-chromene (S-DCM) and diarylethene were synthesized. The detailed investigations on the fluorescence spectra, absorption spectra, and time-dependent density functional theory calculations (DFT/TD-DFT) were presented. The encapsulation of mPEG2000-DSPE effectively increased the solubility of all the as-prepared samples. The results of TEM showed that the nanoparticles had a good dispersion coefficient. All the nanomaterials (S-DCM-1O@PEG, S-DCM-2O@PEG, S-DCM-3O@PEG, and S-DCM-4O@PEG) exhibited near-infrared emission (650–900 nm) and thus reduced light damage and light scattering for cell imaging in biological applications. Furthermore, PLL (poly- L -lysine hydrobromide) was used to modify the surface of nanoparticles to facilitate easy uptake by A549 cells by changing their electronegativity. The results suggested that S-DCM-2O@PEG@PLL was a highly suitable candidate for cell imaging because of its low toxicity and excellent biocompatibility. [ABSTRACT FROM AUTHOR]

A novel probe T - 1 for the response of NTR based on fused four-ring quinoxaline skeleton was investigated. Under the action of NTR, the probe produced green fluorescence response at 495 nm. The spectroscopic properties, response mechanism, fluorescence imaging, and other aspects of probe T - 1 were investigated. In the fluorescence titration experiments, the probe showed excellent selectivity, lower detection limit (41 ng/mL) and better fluorescence quantum yield (Y u = 0.14) for NTR. The response mechanism of the probe was explained by the comparison of F - 1 ultraviolet spectra obtained in two different ways and the verification of HRMS spectra. Additionally, the application of fluorescence imaging technology made it possible to detect endogenous NTR, and broadened the application prospect of fluorescent probe. We have designed a novel probe T - 1 for the response of NTR based on fused four-ring quinoxaline skeleton. Probe T - 1 showed excellent selectivity, lower detection limit (41 ng/mL) and better fluorescence quantum yield (Y u = 0.14) for NTR. The application of fluorescence imaging technology made it possible to detect endogenous NTR, and broadened the application prospect of fluorescent probe. [Display omitted] • The probe T - 1 can detect NTR with high sensitivity and selectivity. • The detection limit is as low as 41 ng/mL with high accuracy. • The probe shows low toxicity and is successfully employed to monitor NTR in vivo. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel fused four-ring quinoxaline was applied as the skeleton to detect H 2 O 2. • High selectivity towards H 2 O 2 in both independent and coexistence systems. • Low detection limit, wide pH tolerance, and low toxicity. • A designed off–on process for H 2 O 2 imaging in living cells. Hydrogen peroxide (H 2 O 2), a member of small-molecule reactive oxygen species (ROS), plays vital roles in normal physiological activities and the occurrence of many diseases. In this work, two off–on fluorescent probes, QX8A-H 2 O 2 and QX9A-H 2 O 2 , were firstly designed for H 2 O 2 detection with novel fused quinoxalines as the fluorophores and boronate moiety as the reaction sites. By comparing the optical properties, QX9A-H 2 O 2 with better performance was selected for further studies. QX9A-H 2 O 2 exhibited a high sensitivity to H 2 O 2 with the detection limit as low as 46 nM, and displayed a good selectivity towards H 2 O 2 over other reactants such as ROS, biothiols and various ions. The detection was based on the intramolecular charge transfer (ICT), proceeding through a sequential oxidative hydrolysis, 1,6-rearrangement elimination and decarboxylation process to release the fluorophore QX9A. Moreover, probe QX9A-H 2 O 2 was cell permeable and was successfully employed in both exogenous and endogenous H 2 O 2 imaging in living cells. [ABSTRACT FROM AUTHOR]

In situ imaging of nitric oxide (NO) is of great importance to study the critical roles of NO in various physiological and pathological processes. In most currently available fluorescent probes for NO, the o-phenylenediamine (OPD) based derivatives are the most greeted and studied, in which the OPD serves as the reactive site and fluorescence quencher to modulate a turn-on process via photoinduced electron transfer (PET). In this work, a unique turn-off probe containing OPD moiety, N-1 , was designed and synthesized, which was radically different from the typical PET-based turn-on fluorescent probes. By theoretical calculation of molecular orbital, it was verified that not the widely used PET mechanism, but the intramolecular charge transfer (ICT) mechanism should be responsible for the turn-off process. Probe N-1 exhibited a remarkable performance with 7-folds fluorescence intensity decrease (at 490 nm), a low detection limit (20 nM), a fast response to NO within 12 min and a high selectivity for NO over other relevant analytes. Furthermore, probe N-1 was also applied to imaging NO in living cells. All results demonstrated that the new probe N-1 could be a practical and ideal NO indicator with good biological significance. [Display omitted] • O-phenylenediamine-hemicyanine-based probe for NO with a unique turn-off property. • Theoretical calculation verified ICT rather than PET induced the turn-off process. • High selectivity towards NO with low detection limit and short response time. • N-1 was of low toxicity and successfully applied in cell imaging for NO detection. [ABSTRACT FROM AUTHOR]

• A colorimetric and ratiometric fluorescent probe for highly selective recognition of Hg2+ was synthesized. • The probe could detect Hg2+ in living cells. • The emission peak red shifted 109 nm upon addition of Hg2+. Although fluorescent probes had become powerful tools to detect and image mercury ion (Hg2+), most of them suffered from a single signal change. Therefore, a new ratiometric fluorescent probe 1, with a quinoline–benzothiazole group as donor and a rhodamine as acceptor, was constructed for Hg2+ detection in this paper study. Results showed that Probe 1 was highly sensitive and selective to Hg2+, with a linear range of 0–26 μM and a detection limit (LOD) of 0.2 μM. Moreover, with excess competitive metal ions in DMF–H 2 O (v/v, 7/3), probe 1 exhibited excellent colorimetric selectivity and sensitivity to Hg2+ with the significant color change from colorless to pink with a linear range 0–28 μM and a LOD of 0.37 μM, because Hg2+ promoted the rhodamine hydrazide opening. And probe 1 finally was used to detect Hg2+ in living cells. [ABSTRACT FROM AUTHOR]