A Thiosemicarbazone-Derived Fluorescent Probe for the Detection of Silver Ions and Bioimaging Application.

Phosphorescence shows great potential for application in bioimaging and ion detection because of its long-lived luminescence and high signal-to-noise ratio, but establishing phosphorescence emission in aqueous environments remains a challenge. Herein, we present a general design strategy that effectively promotes phosphorescence by utilising water molecules to construct hydrogen-bonded networks between carbon dots (CDs) and cyanuric acid (CA). Interestingly, water molecules not only cause no phosphorescence quenching but also greatly enhance the phosphorescence emission. This enhancement behaviour can be explained by the fact that the highly ordered bound water on the CA particle surface can construct robust bridge-like hydrogen-bonded networks between the CDs and CA, which not only effectively rigidifies the C=O bonds of the CDs but also greatly enhances the rigidity of the entire system. In addition, the CD-CA suspension exhibits a high phosphorescence lifetime (687 ms) and is successfully applied in ion detection based on its visible phosphorescence.

Tripodal "broom" molecule derivatives containing π electrons were used as ionophores of silver ion-selective electrodes. The ability of the electrodes to detect silver ions was evaluated using the Nernst equation. When allyl- and propargyl-type tripodal broom molecules, and a propargyl-type monopodal analog were used in the electrode, Nernstian responses for silver ions were observed, indicating that π electrons play an important role in the detection of silver ions. In the presence of interfering metal ions, the selectivity for silver ions was affected by the number and density of π electrons in the ionophore. The electrode containing the allyl-type tripodal broom molecule was used to accurately determine the concentration of glucosamine hydrochloride in a real sample.

Molecular imaging is a powerful tool to visualize cellular processes and activity levels of biomarkers at the cellular and molecular level, in which a molecular probe is a prerequisite for the molecular imaging technique. The present work reports a bimodal probe for the fluorescence and magnetic resonance detection of fluoride ions (F-) in aqueous media and in vivo. The bimodal probe, EDTA-Gd-HF, was prepared by self-assembly of the EDTA-Gd complex with 3-hydroxyflavone (HF). In the system, HF plays the role of spectroscopic reporter and Gd(iii) serves as a MRI signal output unit as well as the fluoride ion binding site. Upon addition of fluoride ions into an aqueous solution of EDTA-Gd-HF, the replacement of one coordinated water molecule and then liberation of HF led to remarkable spectroscopic recovery and distinct changes to the longitudinal relaxivity (r1), by which fluorescence/MRI bimodal fluoride ion sensing was achieved. In vivo magnetic resonance imaging (MRI) in mice indicates that EDTA-Gd-HF can be potentially used in biomedical diagnosis and therapy fields.

A colorimetric and turn-on NIR fluorescent probe based on xanthene system for sensitive detection of thiophenol and its application in bioimaging

Intracellular redox homeostasis exerts a tremendous influence on pathophysiological fields. In order to maintain the homeostasis of intracellular redox state, reactive oxygen species (ROS) and reactive sulfur species (RSS) react and transform with each other, and their levels also directly reflect the degree of oxidative stress and disease. To understand the correlation and pathophysiological effects of these two signaling molecules in oxidative stress, unique fluorescence imaging tools are required. Fluorescent probes have become an indispensable detection tool in modern scientific research and disease diagnosis. Currently, there are many fluorescent probes for detecting ROS or RSS. However, the cellular environment is extremely complex. Dual detection fluorescent probes that can monitor more than one species in a biological environment cause our attention. This review describes dual detection fluorescent probes that can detect ROS and RSS simultaneously or sequentially. This will provide strong support for the study of redox homeostasis.

Sesame-derived ions co-doped fluorescent carbon nanoparticles for bio-imaging, sensing and patterning applications

Ion beam induced fluorescence imaging in biological systems

The bipyridine-based constructs 4-(pyridine-2-yl)-3H-pyrrolo[2,3-c]quinoline (PPQ) and [6-(3H-pyrrolo[2,3-c]quinolin-4-yl)pyridin-2-yl]methanol (PPQ-OH) and their assemblies with surfactants are evaluated as turn-on fluorescent sensors for Zn2+ ions in aqueous solution. This study strives to overcome the problem of low water solubility of the hydrophobic PPQ and PPQ-OH by using micelles. Whereas the ligands show selective sensing behavior for Zn2+ over important biological cations including Na+ , K+ , Ca2+ , Mg2+ in anionic sodium dodecyl sulfate and non-ionic Tween 80 micelles, no Zn2+ sensing is observed in cationic cetyltrimethylammonium bromide micelles. Unlike in DMF, Cd2+ interference is observed in aqueous conditions, which can be avoided either by performing the study at pH≥9 or by carrying out a time-resolved fluorescence study. Analysis of the Job plot data, the fluorescence lifetimes, and experiments on varying micellar shape and pH, confirms that the coordination volume of the resulting octahedral metal complex and formation of a five-membered chelate ring are critical factors for Cd2+ interference. The described sensing systems are capable of detecting Zn2+ ions at the micromolar level. Additionally, it is shown that PPQ and PPQ-OH can be used to detect Zn2+ in HeLa cells under physiological conditions in bioimaging studies.

Tripeptide and phenylboronic acid-functionalized eco-friendly carbon dots for dual sensing of dopamine and their bioimaging applications in SH-SY5Y cells

The specificity detection of Al3+ is important for monitoring life health and environmental pollution. A fluorescence enhancement probe based on caffeic acid HAM was synthesized for detecting Al3+ with high sensitivity and good selectivity. When Al3+ was added in the aqueous solution of HAM, the formation of HAM-Al3+ complexes inhibited the PET process, which led to great enhancement of fluorescence. The addition of other metal ions cannot induce the change of fluorescence intensity. The sensing mechanism was proved by 1H NMR titration, MS, and Job's plot. Moreover, probe HAM exhibited excellent properties, such as high sensitivity (LOD = 0.168 μM), fast response time (30 s), wide pH range (3-11), and good interference ability. Based on the above results, probe HAM was used to explore its bioimaging application in biological samples.

A convenient green method to synthesize luminescent carbon dots from edible carrot and its application in bioimaging and preparation of nanocatalyst

A sensitive nonenzymatic chemiluminescence method was developed for the detection of silver ions. The assay is based on chemiluminescence resonance energy transfer (CRET) between luminol and fluorescein with the formation of a ternary complex between fluorescein, phenanthroline (Phen) and silver ion. Standard solutions containing silver ions in the concentration range of 1.0 × 10−7 M to 2.5 × 10−4 M were examined by the proposed procedure and it was observed that the calibration curve obtained was linear in this range with a correlation coefficient of 0.9993. The detection limit for silver ion was estimated to be 5.0 × 10−8 M. Advantages of the proposed method is its high selectivity and low detection limits compared with other methods.

Lanthanide upconversion nanoparticles and applications in bioassays and bioimaging: A review

My thesis is focused on the development of fluorescent probes for biosensing and bioimaging within specific organelles. My main research efforts are mainly focused on the design, synthesis and biological applications of these new molecular probes. These new fluorescent probes I developed can be manipulated through the chemical modifications for binding to specific organelles capable of reporting localized bioinformation. Compared to the currently commercially available organelle-specific fluorescent stains, the advantages of the newly synthesized fluorescent probes include low cytotoxicity, high photostability, and long fluorescence lifetimes. These features are crucial for long-time tracking study of biological processes. Research on fluorescent probes with both analyte responsiveness and organelle targetability is a new and emerging area that has attracted increasing attention over the past few years. Because of their high sensitivity, specificity and fast response, these novel fluorescent probes have been proven to be useful tools for facilitating biomedical research. I have further extended the diversity by developing organelle-specific responsive probes capable of detecting changes in biomolecular levels and the microenvironment. My future research efforts give more considerations of the “low-concern” organelles, such as the Golgi apparatus, the endoplasmic reticulum, and ribosomes. Considering the tiny sizes of subcellular organelles, we anticipate that better visualization of the cellular events within specific organelles will rely on super-resolution optical microscopy with nanoscopic-scale resolution.

Facile green and one-pot synthesis of purple perilla derived carbon quantum dot as a fluorescent sensor for silver ion