Chusheng Huang

Synthesis, Characterization, and Anticancer Activity of a Series of Ketone-N4-Substituted Thiosemicarbazones and Their Ruthenium(II) Arene Complexes

A series of ketone-N(4)-substituted thiosemicarbazone (TSC) compounds (L1-L9) and their corresponding [(η(6)-p-cymene)Ru(II)(TSC)Cl](+/0) complexes (1-9) were synthesized and characterized by NMR, IR, elemental analysis, and HR-ESI-mass spectrometry. The molecular structures of L4, L9, 1-6, and 9 were determined by single-crystal X-ray diffraction analysis. The compounds were further evaluated for their in vitro antiproliferative activities against the SGC-7901 human gastric cancer, BEL-7404 human liver cancer, and HEK-293T noncancerous cell lines. Furthermore, the interactions of the compounds with DNA were followed by electrophoretic mobility spectrometry studies.

A ratiometric nanosensor based on fluorescent carbon dots for label-free and highly selective recognition of DNA

A ratiometric nanosensor for label-free and highly selective recognition of DNA was reported in this work, by employing fluorescent carbon dots (CDs) as the reference fluorophore and ethidium bromide (EB), a specific organic fluorescent dye toward DNA, playing the role of both a specific recognition element and response signal. Fluorescent CDs were synthesized through a microwave irradiation technique. When EB was present, the fluorescence of CDs was quenched effectively due to the electron transfer process between CDs and EB, while the fluorescence of EB was increased partially without fluorescence resonance energy transfer under same excitation wavelength. Upon the addition of DNA, the fluorescence of EB was enhanced dramatically but the fluorescence intensity of CDs stayed almost constant, leading to a ratiometric detection of DNA. This fluorescent nanosensor exhibited good sensitivity, a broad dynamic linear range of 1.0 μM–100 μM, and low detection limit down to 0.47 μM. The relative standard deviation for 30 μM DNA was 0.2% (n = 5). The present ratiometric nanosensor also showed high accuracy and excellent selectivity for DNA over some chemical substances, such as amino acids, nucleotides, proteins, and RNA. The proposed method was applied to the determination of DNA in synthetic samples with satisfactory results. The proposed DNA detection method was quite simple, rapid and convenient due to the elimination of the modification and separation procedures. The possible fluorescence quenching mechanism was further investigated.

A CdTe/CdS/ZnS core/shell/shell QDs-based "OFF- ON" fluorescent biosensor for sensitive and specific determination of L-ascorbic acid

Herein we report a quantum dots (QDs)-based “OFF–ON” fluorescent biosensor for the sensitive and specific determination of L-ascorbic acid. The proposed one-pot L-ascorbic acid detection method is quite simple, rapid and convenient because of the elimination of the modification and separation procedures. In this contribution, the N-acetyl-L-cysteine (NAC)-capped CdTe/CdS/ZnS core/shell/shell QDs were synthesized in aqueous phase. Subsequently, KMnO4 was added into solution and attached to the QDs surface to effectively quench the fluorescence of the QDs, which rendered the QDs into fluorescence “OFF” status. After the addition of L-ascorbic acid into the QDs–KMnO4 system, the fluorescence of the QDs was then turned “ON” because L-ascorbic acid could bind with KMnO4 and break KMnO4 away from the surface of the QDs. Under the optimized conditions, the relative restored fluorescence intensity was directly proportional to the concentration of L-ascorbic acid in the range of 8.0 × 10−9 M to 1.0 × 10−7 M, with a correlation coefficient of 0.9971 and a limit of detection of 1.8 × 10−9 M. The relative standard deviation for 6.0 × 10−8 M L-ascorbic acid was 2.1% (n = 5). There was almost no interference from few common ions, carbohydrates, nucleotides and amino acids. The proposed method was applied to the determination of L-ascorbic acid in three synthetic samples, human urine samples and vitamin C tablets with satisfactory results. The possible fluorescence quenching mechanism of this fluorescent sensor was further investigated by UV-vis spectroscopy.

Combined spectroscopy and cyclic voltammetry investigates the interaction between [(η6-p-cymene)Ru(benzaldehyde-N(4)-phenylthiosemicarbazone)Cl]Cl anticancer drug and human serum albumin

In this article, the interaction between [(η6-p-cymene)Ru(benzaldehyde-N(4)-phenylthiosemicarbazone)Cl]Cl anticancer drug and human serum albumin (HSA) was investigated systematically under physiological conditions by using some spectroscopic methods (UV-vis absorption spectroscopy, fluorescence spectroscopy, FT-IR spectroscopy, CD spectroscopy), mass spectroscopy and cyclic voltammetry. The experimental results indicated that this anticancer drug could quench the intrinsic fluorescence of HSA through static quenching mechanism. The Stern–Volmer quenching model has been successfully applied, and the Stern–Volmer quenching constants together with the modified Stern–Volmer quenching constants at different temperatures were also calculated. The corresponding thermodynamic parameters ΔH, ΔG and ΔS were also calculated. The binding of this anticancer drug and HSA resulted in the formation of drug–HSA complex, and the electrostatic interaction played a major role in the complex stabilization. The distance r between the donor (HSA) and the acceptor (drug) was obtained through fluorescence resonance energy transfer theory. Competitive experiments indicated that the binding site of this anticancer drug to HSA was located at site I. The results of synchronous fluorescence spectra, three-dimensional fluorescence spectra, FT-IR spectra and CD spectra indicated that the microenvironment and the conformation of HSA were changed noticeably due to the presence of this anticancer drug. The results of mass spectra and cyclic voltammetry further confirmed the interaction between HSA and this anticancer drug. These results indicated that the biological activity of HSA was dramatically affected by the [(η6-p-cymene)Ru(benzaldehyde-N(4)-phenylthiosemicarbazone)Cl]Cl anticancer drug.

Systematical investigation of in vitro molecular interaction between fluorescent carbon dots and human serum albumin

Fluorescent carbon dots (CDs) have been widely applied in biological and biomedical applications due to their superior properties. Therefore, for any in vivo biomedical application, the thermodynamic and kinetic information of in vitro molecular interaction between CDs and human serum albumin (HSA) is very important and need to be elucidated deeply. In this work, in vitro molecular interaction between CDs and HSA was systematically investigated by spectroscopic techniques and electrochemical approaches. CDs with maximum emission of 437 nm were synthesized by microwave technique through a one-pot process. Some important thermodynamic and kinetic parameters were calculated, and the binding interaction between HSA and CDs was further explored by electrochemical approaches. The binding interaction of CDs with HSA was resulted from the complex formation of HSA–CDs. Hydrogen bonding and van der Waals interactions played major roles during HSA–CDs complex stabilization. The primary binding site of CDs was mainly located within site I (subdomain IIA) of HSA. The micro-environmental and conformational changes of HSA induced by CDs were investigated by multi-spectroscopic methods. These data suggested that the conformational change of HSA was significantly at secondary structure level and the biological activity of HSA was weakened dramatically in the present of CDs.

Molecular interaction investigation between three CdTe:Zn(2+) quantum dots and human serum albumin: A comparative study.

Water-soluble Zn-doped CdTe quantum dots (CdTe:Zn(2+) QDs) have attracted great attention in biological and biomedical applications. In particular, for any potential in vivo application, the interaction of CdTe:Zn(2+) QDs with human serum albumin (HSA) is of greatest importance. As a step toward the elucidation of the fate of CdTe:Zn(2+) QDs introduced to organism, the molecular interactions between CdTe:Zn(2+) QDs with three different sizes and HSA were systematically investigated by spectroscopic techniques. Three CdTe:Zn(2+) QDs with maximum emission of 514 nm (green QDs, GQDs), 578 nm (yellow QDs, YQDs), and 640 nm (red QDs, RQDs) were tested. The binding of CdTe:Zn(2+) QDs with HSA was a result of the formation of HSA-QDs complex and electrostatic interactions played major roles in stabilizing the complex. The Stern-Volmer quenching constant, associative binding constant, and corresponding thermodynamic parameters were calculated. The site-specific probe competitive experiments revealed that the binding location of CdTe:Zn(2+) QDs with HSA was around site I. The microenvironmental and conformational changes of HSA induced by CdTe:Zn(2+) QDs were analyzed. These results suggested that the conformational change of HSA was dramatically at secondary structure level and the biological activity of HSA was weakened in the present of CdTe:Zn(2+) QDs with bigger size.

Systematic investigation of interactions between papain and MPA-capped CdTe quantum dots

Fluorescent quantum dots (QDs) have been widely applied in biological and biomedical areas, but relatively little is known about the interaction of QDs with some natural enzymes. Herein, the interactions between 3-mercaptopropionic acid-capped CdTe QDs (MPA-QDs) and papain were systematically investigated by UV–Vis absorption spectra, fluorescence spectra and circular dichroism (CD) spectra under the physiological conditions. The fluorescence spectra results indicated that MPA-QDs quenched the fluorescence intensity of papain. The modified Stern–Volmer quenching constant Ka at different temperatures and the corresponding thermodynamic parameters ΔH, ΔG and ΔS were also calculated. The binding of MPA-QDs and papain is a result of the formation of QDs-papain complex and the electrostatic interactions play a major role in stabilizing the complex. The CD technique was further used to analyze the conformational changes of papain induced by MPA-QDs and the results indicated that the biological activity of papain was affected by MPA-QDs dramatically.

In vitro interaction investigation between three Ru(II) arene complexes and human serum albumin: structural influences

Ru(II) arene complex-based anticancer drugs have attracted great attention in biomedical and pharmacological areas. The investigation of structural influences helps in understanding biological effects and in contributing to the development of new drugs. The study of protein–drug interactions is very important for understanding the mechanism behind the bioactivities of drugs. To examine the potential of Ru(II) arene complexes as therapeutics, we systematically investigated the structural influences of three Ru(II) arene complexes (Ru-1, Ru-2, and Ru-3) based on their in vitro interaction with human serum albumin (HSA) by multi-spectroscopic methods. The binding interactions of three drugs with HSA results in the formation of three HSA–drug complexes, and van der Waals forces and hydrogen bonding played major roles in stabilizing these complexes. The changes of micro-environments and conformations of HSA were significant and the biological activity of HSA was weakened when present in the three drugs. We found that a number of Ru(II) arene groups and space steric hindrance were responsible for the differences in the in vitro interactions between different Ru(II) arene complexes and HSA. Our results together provide further molecular level understanding of binding interactions of protein with Ru(II) arene complexes and a strategy for the research of structural influences.

Novel N-Doped Carbon Dots/β-Cyclodextrin Nanocomposites for Enantioselective Recognition of Tryptophan Enantiomers

Based on N-doped carbon dots/β-cyclodextrin nanocomposites modified glassy carbon electrodes (N-CDs/β-CD/GCE), an effective electrochemical sensor for enantioselective recognition of tryptophan (Trp) enantiomers was developed by differential pulse voltammograms (DPVs). Fluorescent N-CDs were synthesized through a hydrothermal method and characterized by spectroscopic approaches. The N-CDs/β-CD nanocomposites were efficiently electrodeposited on the surface of GCE through C–N bond formation between N-CDs and electrode. The obtained N-CDs/β-CD/GCE was characterized by multispectroscopic and electrochemical methods. Such N-CDs/β-CD/GCE generated a significantly lower Ip and more negative Ep in the presence of l-Trp in DPVs, which was used for the enantioselective recognition of Trp enantiomers. The N-CDs/β-CD nanocomposites showed different binding constants for tryptophan enantiomers, and they further selectively bonded with l-Trp to form inclusion complexes. This N-CDs/β-CD/GCE combined advantages of N-CDs with strong C–N binding ability and β-CD with specific recognition of Trp enantiomers to fabricate a novel sensing platform for enantioselective recognition of Trp enantiomers. This strategy provided the possibility of using a nanostructured sensor to discriminate the chiral molecules in bio-electroanalytical applications.

Systematical investigation of binding interaction between novel ruthenium(II) arene complex with curcumin analogs and ctDNA.

In this study, the interaction between a novel ruthenium(II) arene complex with curcumin analogs and calf thymus DNA (ctDNA) was investigated systematically by viscosity measurement, the DNA melting approach, multispectroscopic techniques and electrochemical methods. The absorption spectra of the ctDNA-drug complex showed a slight red shift and a weak hypochromic effect. The relative viscosity and melting temperature of ctDNA increased on addition of the drug. The evidence obtained from fluorescence competitive experiments indicated that the binding mode of the drug with ctDNA was intercalative. Using acridine orange (AO) as a fluorescence probe, the drug statically quenched the fluorescence of the ctDNA-AO complex, and hydrogen bonding and van der Waals interactions played vital roles in the binding interaction between the drug and ctDNA. The influences of ionic strength, chemical denaturants and pH on the binding interaction were also investigated. Circular dichroism and Fourier transform infrared spectra suggested that this drug might bond with the G-C base pairs of ctDNA and the right-handed B-form helicity of ctDNA remained after drug binding. The intercalative binding between the drug and ctDNA was further investigated using electrochemical techniques. All these results suggested that the biological activity of ctDNA was affected by ruthenium(II) arene complex with curcumin analogs. Copyright