Studies on the interaction of protein with acid chrome blue K by electrochemical method and its analytical application

The toxicity response of the electrochemical signal of the cell to the drug metabolized by the S9 system

The electrochemical detection method of cytotoxicity using intracellular purines as biomarkers has shown great potential for in vitro drug toxicity evaluation. However, no electrochemical detection system based on an in vitro drug metabolism mechanism has been devised. In this paper, electrochemical voltammetry was used to investigate the effect of the S9 system on the electrochemical behavior of HepG2 cells, and benzo[a]pyrene, fluoranthene, and pyrene were employed to investigate the sensitivity of electrochemical signals of cells to the cytotoxicity of drugs metabolized by the S9 system. The results showed that, within 8 h of exposure to the S9 system, the electrochemical signal of HepG2 cells at 0.7 V did not alter noticeably. The levels of xanthine, guanine, hypoxanthine, and adenine in the cells were not significantly altered. Compared with the absence of S9 system metabolism, benzo[a]pyrene and fluoranthene processed by the S9 system decreased the electrochemical signal of the cells in a dose-dependent manner, while pyrene did not change it appreciably. HPLC also revealed that benzo[a]pyrene and fluoranthene metabolized by the S9 system decreased the intracellular purine levels, whereas pyrene had no effect on them before and after S9 system metabolism. The cytotoxicity results of the three drugs examined by electrochemical voltammetry and MTT assay showed a strong correlation and good agreement. The S9 system had no effect on the intracellular purine levels or the electrochemical signal of cells. When the drug was metabolized by the S9 system, variations in cytotoxicity could be precisely detected by electrochemical voltammetry.

A label-free approach to detect cell viability/cytotoxicity based on intracellular xanthine/guanine by electrochemical method

INTRODUCTION

Cell viability and cytotoxicity is one of the most important toxicology indicators. In this study, an electrochemical method for detecting cell viability and cytotoxicity was discussed with the intracellular small molecule metabolite purines as indexes.

METHODS

The electrochemical behaviors of Balb/c 3T3, CHO, PC-12 and V79 cell suspensions were studies by cyclic voltammetry, and cell viability and cytotoxicity of four cell lines were compared by electrochemical, cell counting, 3-(4,5-dimethyl-2-Thiazyl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT) and trypan blue exclusion methods.

RESULTS

Four cell lines all showed an oxidation peak derived from mixture of xanthine and guanine at about 0.7 V. Using intracellular xanthine and guanine as index, the electrochemical method could not only describe the cell growth curves of four cell lines, but also reflect the changes of cell viability at various phases of the cell growth prior to the counting method. Compared with MTT, cell counting and trypan blue staining methods, the electrochemical method could detect the cytotoxicity of carcinogen earlier and more sensitively.

DISCUSSION

The electrochemical method could track the change of intracellular xanthine and guanine contents, and used it as index to detect cell viability and cytotoxicity at the molecular level without markers, showing greater advantages over the method with apparent cell proliferation as the endpoint.

Unzipped carbon nanotubes: analytical and binding applications of semisynthetic phlebotropic flavonoid, diosmin

Present study describes the utility of unzipped carbon nanotubes as electrochemical sensing platform for the determination of diosmin in pharmaceutical formulations and for the investigation of its binding to human serum albumin.

Binding and conformational changes of human serum albumin upon interaction with 4-aminoantipyrine studied by spectroscopic methods and cyclic voltammetry

The interactions of 4-aminoantipyrine (AAP) with human serum albumin (HSA) have been studied by UV-visible spectroscopy, fluorescence spectroscopy and cyclic voltammetry. The binding of 4-aminoantipyrine quenches the HSA fluorescence, revealing a 1:1 interaction with a binding constant of about 10(5) M(-1). The experimental results showed that AAP effectively quenched the intrinsic fluorescence of HSA via dynamic type of quenching. In addition, according to the synchronous fluorescence spectra of HSA in presence of 4-aminoantipyrine, the tryptophan residue of the proteins are most perturbed by the binding process. The number of binding sites, the binding constant, site probe study, some common metal ions effect and the thermodynamic parameters were calculated.

Characterization of the interaction between 4-(tetrahydro-2-furanmethoxy)-N-octadecyl-1,8-naphthalimide and human serum albumin by molecular spectroscopy and its analytical application

A novel 4-(tetrahydro-2-furanmethoxy)-N-octadecyl-1,8-naphthalimide (TNN) was synthesized as a spectrofluorimetric probe for the determination of proteins. The effect of different solvents on the spectral characteristics of TNN was investigated. The results showed that TNN displayed dependent solvent polarity properties due to the effect of internal charge transfer. The interactions between TNN and human serum albumin (HSA) were studied by fluorescence and absorption spectroscopy. Fluorescence data revealed that the fluorescence quenching of HSA by TNN was the result of the formation of TNN-HSA complex. The binding parameters of interactions between TNN and HSA at different temperatures were obtained according to the Stern-Volmer equation. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS), for the interactions were calculated to be -7.31 kJ mol(-1) and 72.75 J mol(-1) K(-1) according to the van't Hoff equation, indicating that the hydrogen bonds and hydrophobic interactions were the dominant intermolecular force in stabilizing the complex. The effect of TNN on the conformation of HSA was analyzed by circular dichroism and synchronous fluorescence spectroscopy. Furthermore, the results of displacement experiments using warfarin indicated that TNN could bind to site I of HSA. The fluorescence of TNN could be largely quenched by HSA, based on which a new fluorometric method for detecting HSA in the HCl-Tris buffer solution (pH = 7.4) was developed. The linear ranges of the calibration curves were 0.1~14.2 μM for HSA, 0.1~13.0 μM for bovine serum albumin (BSA), 0.2~9.7 μM for γ-globulin, and 0.3~11.3 μM for hemoglobin (Hb), with detection limits (3σ) of 1.37 × 10(-10) M for HSA, 1.84 × 10(-10) M for BSA, 3.14 × 10(-10) M for γ-globulin, and 6.86 × 10(-10) M for Hb. The effect of metal cations on the fluorescence spectra of TNN in ethanol was also investigated. The method has been applied to the determination of total proteins in human serum samples collected from the hospital and the results were in good agreement with those reported by the hospital.

Ultrasensitive determination of serum albumin using resonance light scattering based on ZnS-polyacrylic acid nanoparticles

ZnS-polyacrylic acid (ZnS-PAA) was prepared by an in situ polymerization method using nano-ZnS as core in the presence of acrylic acid (AA), and ZnS-PAA nanoparticles was characterized by ultraviolet spectrometry (UV) and transmission electron microscopy (TEM). Based on the significant increase of the resonance light scattering (RLS) intensity with the interaction between nanoparticles and serum albumin, RLS method was developed for the sensitive determination of serum albumin (BSA and HSA). Under optimum conditions, the change of the intensity (DeltaI) of the RLS spectra at lambda=392nm was linearly proportional to the concentration of BSA and HSA. The linear range was 1-100ngmL(-1) for HSA and 1-120ngmL(-1) for BSA, and the limit of detection (LOD) was 0.4ngmL(-1) for HSA and 0.5ngmL(-1) for BSA. This method proved to be very sensitive, rapid, simple and tolerant of most interfering substances.

Determination of proteins with tetracarboxy manganese(II) phthalocyanine by resonance light scattering technique

A novel method for the determination of proteins by using tetracarboxy manganese(II) phthalocyanine (MnC4Pc) as a resonance light scattering (RLS) probe has been developed. At pH 3.0 Britton-Robinson (B-R) buffer solution, the RLS intensity of MnC4Pc at 385 nm is greatly enhanced in the presence of proteins. The effects of pH, reaction time, concentration of MnC4Pc and interfering substances on the enhanced RLS intensity are investigated, respectively. Under optimal conditions, the linear ranges of the calibration curves are 0-2.00 microg mL(-1) for bovine serum albumin (BSA) and human serum albumin (HSA), 0.0-1.75 microg mL(-1) for human-IgG and ovalbumin, with a detection limit of 16.37 ng mL(-1) BSA, 17.62 ng mL(-1) HSA, 19.41 ng mL(-1) human-IgG and 20.72 ng mL(-1) ovalbumin. The method has been applied to the determination of total proteins in human serum samples collected from a hospital and the results are in good agreement with those reported by the hospital.

Simultaneous voltammetry determination of dihydroxybenzene isomers by poly-bromophenol blue/carbon nanotubes composite modified electrode

A novel modified electrode was constructed by electropolymerization of bromophenol blue at a multi-walled carbon nanotubes modified glassy carbon electrode. The electrode developed was used for the simultaneous determination of the isomers of dihydroxybenzene in environmental samples using a voltammetry method. There was a linear relationship over the range 10(-6)-10(-4 )mol L(-1) of hydroquinone, catechol and resorcinol; the detection limits was 3 x 10(-7) mol L(-1). The constructed electrode showed excellent reproducibility and stability. Actual water samples were analyzed and satisfactory result was obtained.