Yingqi Li

Study on the Interaction between 3 Flavonoid Compounds and α-Amylase by Fluorescence Spectroscopy and Enzymatic Kinetics

The interaction between alpha-amylase and 3 flavonoid compounds from tartary buckwheat bran, namely, quercetin (Que), its monoglycoside isoquercetin (Iso), and its diglycoside rutinb (Rut), has been studied by fluorescence spectroscopy and enzymatic kinetics. The results indicate that Que, Iso, and Rut could bind with alpha-amylase to form a new complex, which exhibits an obvious fluorescence quenching. We deduce that such a quenching is a static quenching via nonradiation energy transfer. Results from plots and calculations show that the sequence of binding constants (KA) is Iso > Que > Rut. Calculation on thermodynamic parameters reveals that the main driving force of above-mentioned interaction is hydrophobic. Enzyme activity measurements show that all of the 3 flavonoid compounds are effective inhibitors toward alpha-amylase, and the inhibitory mode belongs to a competitive type. The sequence of affinity (1/Ki) is in accordance with the results of binding constants (KA) from fluorescence experiments.

A single fluorescent probe for multiple analyte sensing: efficient and selective detection of CN−, HSO3− and extremely alkaline pH

A simple tailor-made water-soluble broadly emitting (500-650 nm) fluorescent probe 3-methyl-2-(N-ethylcarbazole-3vinyl)-benzothiazolium iodide (IECBT) for the selective and sensitive detection of multiple analytes, including CN-, HSO3 - and extremely alkaline pH, is designed and synthesized via the ethylene bridging of 3-formyl-N-ethylcarbazole and 2,3-dimethyl benzothizolium iodide, which is a useful fluorescent probe for monitoring these analytes at extremely low concentrations quantitatively. CN- and HSO3 - are expected to undergo 1,4-addition reactions with the C-4 atom in the ethylene group of IECBT. This water-soluble fluorescent probe exhibits excellent sensitivity and selectivity toward CN- in DMSO, which also results in a prominent fluorescence ratiometric change and a color change. The high selectivity and sensitivity of IECBT toward HSO3 - and extremely alkaline pH over other coexisting species in water are also observed. The titration experiments show that it features a remarkably large Stokes shift and good stability towards CN-, HSO3 - or extremely alkaline pH with a significant fluorescence turn-off response. Importantly, we demonstrate that IECBT can be used for the real-time sensing and bioimaging of CN-, HSO3 - or extremely alkaline pH in living samples.

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

Nitric oxide functions as an important signalling molecule in many biological systems. Nanodiamonds (NDs) have attracted enormous attention in the field of biomaterial science for biosensing applications and drug/gene delivery. In this work, one novel Cu(ii)-based rhodamine B probe for NO detection was composed which was covalently bound to the nanodiamond (ND) surface. The results showed that the covalently conjugated ND probe could detect Cu2+ and NO sequentially with high sensitivity, high stability and good reusability compared to a free rhodamine B probe in CH3CN/HEPES (pH 6.8, v/v, 1 : 1). The detection limit for NO was estimated to be 10.5 nM. In addition, the response to NO was reversible in the presence of O3, which has attracted attention in the fields of biology and environmental science. Further analysis of confocal fluorescence microscopy images and the MTT assay indicated that the conjugated ND probe has favorable biocompatibility and low toxicity. This new Cu2+ and NO selective fluorescent ND probe may have potential applications in environmental science and biology.

Smart pH-responsive and high doxorubicin loading nanodiamond for in vivo selective targeting, imaging, and enhancement of anticancer therapy

Nanodiamond as a carrier for transporting chemotherapy drugs has emerged as a promising strategy for treating cancer. However, several factors have limited its extensive applications in biology, such as low drug loading, tending to aggregate and high drug loss under physiological conditions. In this work, to ensure a high drug capacity and low drug leakage in blood circulation, and especially to ensure that it is delivered to the tumor region, a smart pH-responsive drug delivery system is designed and prepared using doxorubicin (DOX) adsorbed onto PEGylated nanodiamond in sodium citrate medium (ND-PEG-DOX/Na3Cit, NPDC). The system can significantly enhance cellular uptake to exert a therapeutic effect in comparison to the free drug. And more importantly, DOX was released in a sustained and pH-dependent manner, exhibiting excellent stability under physiological conditions. In addition, NPDC could enter into cells via both the clathrin- and caveolae-mediated endocytosis pathways, and then the dissociated DOX migrated into the nucleus to block the growth of cancer cells. Furthermore, NPDC can significantly inhibit cell migration and change the cell cycle. Excitingly, the NPDC system was very smart for the effective enrichment at the tumor site in vivo and enhancing antitumor efficiency with low toxicity beyond conventional DOX treatment in cancer cells and a nude mouse model. So this study introduces a simple and effective strategy to design a promising drug delivery platform for improving the biomedical applications of the smart nanodiamond carriers.

Spectroscopic analysis of the interaction between gallium(III) and apoovotransferrin

Ovotransferrin is a main member of transferrin family and has a dual role in both the transport of iron and antibacterial function. Gallium-67 is widely used as an imaging agent for tumors. It has been reported that Ga(3+) can bind to apoovotransferrin at two sites, one in the N-terminal lobe and another in the C-terminal lobe. However, several details of the interaction between Ga(3+) and apoOTf remain unclear. Here, we report detailed investigations into the interactions of Ga(3+) with apoovotransferrin at the molecular level. First, the characteristics of Ga(3+) binding to apoovotransferrin were analyzed using UV difference spectra. The results show that Ga(3+) prefers to bind to the N-terminal site rather than the C-terminal site under the experimental conditions. Effective stability constants of logK(N)=18.88+/-0.24 and logK(C)=17.65+/-0.12 were determined. Second, conformational changes in apoovotransferrin during Ga(3+) binding were studied using 2-p-toluidinylnaphthalene-6-sulfonate (TNS) as a fluorescence probe. Apoovotransferrin undergoes a large conformational change when Ga(3+) binds to the N-terminal site, and a smaller conformational change when the ion binds to the C-terminal site. UV difference spectra were also used to measure the rate at which EDTA removes Ga(3+) from ovotransferrin carrying one Ga(3+) at the N-terminal site. Ga(3+) removal from the N-terminal binding site follows simple saturation kinetics.

pH-sensitive nanomedicine based on PEGylated nanodiamond for enhanced tumor therapy

Enhancing chemotherapeutic efficiency through enriched drug load and controlled drug release is urgent for alleviating the suffering of cancer patients. Here, a novel pH-sensitive nanomedicine was constructed to acquire high drug loading capacity and better therapeutic efficiency. Interestingly, with the assistance of a pH 8.0 sodium borate buffer solution, PEGylated nanodiamond vehicles loaded with doxorubicin (DOX) achieved nearly 50% loading efficiency, low premature drug release in physiological conditions and effective stimuli-response release under a tumor microenvironment. In addition, assessment by flow cytometry and cell migration assay illustrated that NP/D could induce cell apoptosis, cycle abnormality and inhibit cell migration. The results from the confocal fluorescence microscopy study showed that NP/D could be internalized into cells and distributed into the cytoplasm, subsequently DOX detaches from NP/D and could migrate and enter the nucleus to inhibit cell proliferation. NP/D can open the window for new nanodrugs for a broad spectrum of anticancer agents.

Novel bimetallic gold−silver nanoclusters with “Synergy”-enhanced fluorescence for cyanide sensing, cell imaging and temperature sensing

We herein opened up a facile and green strategy for the fabrication of bright orange-fluorescent gold-silver nanoclusters (AuAgNCs@ew, GSNCs) by a one-pot synthesis at a vital molar ratio of Au/Ag precursors in the egg white protein matrix using microwave-assisted method. The prepared GSNCs exhibited enhanced fluorescence with fluorescent quantum yield of 5.4%, which is dependent on gold and silver synergies. Due to the advantageous superiority of low-toxicity, excellent stability and satisfactory fluorescence, the as-prepared GSNCs has been successfully used in cell imaging and temperature sensing. More strikingly, the GSNCs emerged strong response to CN- with rapid, selective, and ultrasensitive characteristics. The detection limit was approximately 138nM, which is nearly 20 times lower than the maximum level (2700nM) of CN- in drinking water set up by the World Health Organization (WHO). In addition, the as-prepared GSNCs could be applied to detecting real samples with minimum interference. Our findings showed that this new GSNCs probe is eco-friendly and large-scale development for potential applications including the detection of environmental pollution and bioimaging.