A simple lysosome-targeted fluorescent probe based on flavonoid for detection of cysteine in living cells.

Cysteine (Cys) is one of the most important biothiols that plays a crucial role in many physiological and pathological processes, and therefore it is of great importance to detect and analyze Cys in subcellular environments, such as in lysosomes. However, only a few fluorescent probes were reported to be capable of detecting Cys in lysosomes selectively. In this wok, we designed and developed a simple, accessible flavone-based fluorescent probe LFA for detecting Cys in lysosomes. Morpholine was employed as the targeting unit for lysosome, and acrylate group was chosen as the Cys-response unit. The probe was easily prepared by a two-step procedure and displayed large Stokes shift, high sensitivity, turn-on response toward Cys over homocysteine (Hcy), glutathione (GSH), and other amino acids. With low cytotoxicity and good cell permeability, the probe could be successfully applied for fluorescence imaging of Cys in living cells. Furthermore, colocalization experiment revealed that lysosomal-targetable ability of LFA was significant. These results indicated that such simple fluorescent probe could provide a promising tool for detection of lysosomal Cys in living biological systems.

A fluorescent probe with dual acrylate sites for discrimination of different concentration ranges of cysteine in living cells.

Monitoring of cysteine (Cys) is of significant importance for studying Cys-involved biological functions and clinically diagnosing Cys-related diseases. Recently, few fluorescent probes with two different reacting sites were reported to be capable of sensing different concentration ranges of Cys with distinct fluorescence signals, particularly suiting for bioimaging. However, due to relative sophisticated synthesis and moderate selectivity, the applications of these probes were still severely restricted. In this work, we proposed a novel probe design strategy by utilizing two same reacting groups, instead of two different reacting groups, to simplify the synthesis route and minimize the interference from competing species. Same reacting groups in a probe with different steric hindrances could exhibit different reactivities to Cys. This probe showed distinguishable fluorescence peak wavelengths towards low and high concentration ranges of Cys, giving green and blue emissions, respectively. Moreover, this probe was successfully applied for monitoring of Cys concentration in living cells. We believe this work provided a simpler strategy for dual-site fluorescent probes to sense difference concentration ranges of Cys, which may inspire more probe design in future.

Dual-functional AIE fluorescent probes for imaging ß-amyloid plaques and lipid droplets.

Alzheimer's disease (AD) is a chronic neurodegenerative disease. Better imaging and early diagnosis of biomarkers of AD is extremely important for therapeutic interventions. The amyloid cascade hypothesis and its revised version identify insoluble ß-amyloid deposition as a good diagnostic biomarker for AD. Moreover, lipid droplets may also act as an auxiliary biomarker related to AD pathology based on recent studies. Herein, two quinoline-based AIE probes were designed and synthesized for the imaging of Aß plaques and lipid droplets. The probes exhibited remarkable turn-on fluorescence enhancements with the Aß aggregates. The lipid droplets-targeting probe FB exhibited high selectivity and binding affinity towards the Aß aggregates with a detection limit as low as 26.9 nM. Furthermore, FB was capable of readily imaging Aß plaques and lipid droplets at the cellular level and in brain sections of transgenic AD mice. The probe FB can serve as a promising tool for developing early diagnosis and innovative therapeutics of AD.

A near-infrared BODIPY-based fluorescent probe for ratiometric and discriminative detection of Hg2+ and Cu2+ ions in living cells.

A near-infrared distyryl boron dipyrromethene-based sensor bearing one bis(1,2,3-triazole)amino receptor has been synthesized. This probe selectively and quickly binds to Hg2+ and Cu2+ ions in CH3CN/H2O (5:1 v/v) and exhibits remarkably blue-shifted absorption and fluorescence bands due to the inhibition of the intramolecular charge transfer process. The fluorescence changes of this probe upon binding to Hg2+ or Cu2+ ion are totally different, undergoing a ratiometric fluorescence enhancement (for Hg2+) or a fluorescence quenching (for Cu2+) mechanism. The corresponding vivid color changes can be easily seen by the naked eye. This probe was further introduced into Hela cells for living cell imaging and found to discriminate Hg2+ and Cu2+ ions through two near-infrared fluorescence emission channels. These overall results indicate that this Click-derived near-infrared BODIPY-based probe is potentially useful for ratiometric and discriminative detection of Hg2+ and Cu2+ ions in solutions and living cells.

A lysosome-targeting dual-functional fluorescent probe for imaging intracellular viscosity and beta-amyloid.

A lysosome-targeting dual-functional fluorescent probe was rationally designed and developed for imaging intracellular lysosomal viscosity and beta-amyloid. More importantly, the real-time tracking of the dynamic movement of lysosomes, as vesicle structures, has been achieved using Lyso-MC.

Two novel rhodamine-based fluorescent probes for the rapid and sensitive detection of Fe3+: Experimental and DFT calculations.

Fe3+ ions play an important role in both biological and environmental field. In this work, two novel rhodamine-based colorimetric and fluorescent probes (RBA2 and RBA3) were designed and synthesized for the efficient detection of Fe3+. Upon the addition of Fe3+, the fluorescence intensity of RBA2 and RBA3 enhanced 108-fold and 222-fold, respectively. RBA2 and RBA3 exhibited a low detection limit which could achieve 12.8 nM and 11.0 nM. In addition, the binding modes of RBA2 and RBA3 with Fe3+ were proved to be 1:1 stoichiometry in the complexes by Job's plot, ESI-MS and 1H NMR results. The complexing ability of RBA3 with Fe3+ excessed to that of RBA2 that was determined by the binding association constants, and highly consistent with DFT calculations results. Furthermore, RBA2 and RBA3 were further utilized to detect Fe3+ in living cells and real water samples, indicating their promising prospects in biological and environmental field.

Correction: A colorimetric and far-red fluorescent probe for the highly sensitive detection of silver(i).

[This corrects the article DOI: 10.1039/C7RA11933J.].

Neutral merocyanine dyes: for in vivo NIR fluorescence imaging of amyloid-ß plaques.

Two neutral merocyanine-based near-infrared fluorescent probes were for the first time developed through rational engineering of the classical cationic cyanine scaffold IR-780 for in vivo imaging of amyloid-ß plaques. In vivo NIRF imaging revealed that the probe could penetrate the blood-brain barrier and efficiently differentiate the living transgenic and wild-type mice.