Electrochemical study of the interaction of levofloxacin with DNA

A novel electrochemical sensing platform based on double-active-center polyimide covalent organic frameworks for sensitive analysis of levofloxacin

The development of a simple and sensitive electrochemical sensing platform for levofloxacin (LVF) analysis is of great significance to human health. In this work, a covalent organic framework (TP-COF) was in situ grown on the surface of Sn-MoC nanospheres with nanoflower-like morphology through a one-pot method to obtain the TP-COF@Sn-MoC composite. The prepared composite was used to modify a glassy carbon electrode (GCE) to realize the sensitive detection of levofloxacin. TP-COF was formed by polycondensation of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and pyromellitic dianhydride (PMDA), in which C = O and C = N groups served as double active centers for the recognition and electrocatalytic oxidation of the target molecule. Meanwhile, the introduction of Sn-MoC improved the conductivity of the electrode. The TP-COF@Sn-MoC composite produced a strong synergistic effect and showed a high electrocatalytic ability toward levofloxacin oxidation. The linear range of LVF was 0.6-1000 μM and the limit of detection (LOD) was 0.029 μM (S/N = 3). In addition, the sensor has been successfully applied for the analysis of LVF in human urine and blood serum samples with acceptable recovery rates, demonstrating that the sensor was promising in practical applications.

Electrochemical DNA biosensors developed for the monitoring of biointeractions with drugs: a review

The interaction of drugs with DNA is important for the discovery of novel drug molecules and for understanding the therapeutic effects of drugs as well as the monitoring of side effects. For this reason, many studies have been carried out to investigate the interactions of drugs with nucleic acids. In recent years, a large number of studies have been performed to electrochemically detect drug-DNA interactions. The fast, sensitive, and accurate results of electrochemical techniques have resulted in a leading role for their implementation in this field. By means of electrochemical techniques, it is possible not only to demonstrate drug-DNA interactions but also to quantitatively analyze drugs. In this context, electrochemical biosensors for drug-DNA interactions have been examined under different headings including anticancer, antiviral, antibiotic, and central nervous system drugs as well as DNA-targeted drugs. An overview of the studies related to electrochemical DNA biosensors developed for the detection of drug-DNA interactions that were reported in the last two decades in the literature is presented herein along with their applications and they are discussed together with their future perspectives.

Biomass derived nitrogen functionalized carbon nanodots for nanomolar determination of levofloxacin in pharmaceutical and water samples

Binder-free and efficient electrochemical sensing of levofloxacin (LF) was successfully developed based on the nitrogen-doped carbon nanodots (NCNDs). The NCNDs were synthesized by hydrothermal carbonation (180°C for 12 h), and the heteroatom was embedded in aqueous solution of ammonia (NH₃). Spectral and microscopic characteristization techniques were used to analyze the topological, crystallinity, and chemical binding behavior of synthesized biomass functional material. HR-TEM image revealed a uniform spherical dot (2.96 nm), and superior quantum yield efficiency (0.42 Φ). The NCNDs was drop coated on a glassy carbon electrode (GCE) and electrochemical sensing of LF was performed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometric i-t curve in phosphate-buffered saline (PBS; pH = 7.0). The NCNDs modified electrode showed a sharp oxidation peak at +0.95 V (vs. Ag/AgCl) with a four-fold higher current response than the bare GC electrode. The NCNDs/GCE surface not only increases the current response, but has lower detection potential, and facilitates electron transfer reaction. Under optimized working parameters, the NCNDs/GCE showed wide linear concentrations range from 200 nM to 2.8 mM and a low detection limit (LOD) of 48.26 nM (S/N = 3). The electrode modified with NCNDs has high electrochemical sensing stability (RSD = 1.284 ± 0.05% over 5 days), and superior reproducibility (RSD = 1.682 ± 0.06% (n = 3)). Finally, the NCNDs modified GC electrode was successfully applied to quantify the concentration of LF in drug and river water samples with acceptable recovery percentages of 96.60-99.20% and 97.20-99.00% (n=3), respectively.

An Innovative Simple Electrochemical Levofloxacin Sensor Assembled from Carbon Paste Enhanced with Nano-Sized Fumed Silica

A new electrochemical sensor for the detection of levofloxacin (LV) was efficiently realized. The aim was to develop a new, cheap, and simple sensor for the detection of LV, which is used in various infections due to its pharmacological importance. It consists of carbon paste (CP) enhanced with nano-sized fumed silica (NFS). NFS has a very low bulk density and a large surface area. The carbon paste-enhanced NFS electrode (NFS/CPE) showed great electrocatalytic activity in the oxidation of 1.0 mM LV in Britton–Robinson buffer (BR) at pH values ranging from 3.0 to 8.0. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used; the peak current value (I_p) of the NFS/CPE sensor was 2.7 times that of the bare electrode, ensuring its high electrocatalytic activity. Electrochemical impedance spectroscopy (EIS) was performed at a peak potential (E_p) of +1066 mV, yielding a resistance of 10 kΩ for the designed NFS/CPE sensor compared to 2461 kΩ for the bare electrode, indicating the high conductivity of the modified sensor and verifying the data observed using the CV technique. Surface descriptions were determined by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The variation in the concentration of LV (2.0 to 1000 µM) was considered in BR buffer (pH = 5.0) at a scan rate (SR) of 10 mV/s by the NFS/CPE. The detection and quantification limits were 0.09 µM and 0.30 µM, respectively. To evaluate the application of LV in real samples, this procedure was established on Quinostarmax 500 mg tablets and human plasma samples. Reasonable results were obtained for the detection of LV.

A short review of human exposure to antibiotics based on urinary biomonitoring

Antibiotics play a role in preventing and treating infectious diseases and also contribute to other health risks for humans. With the overuse of antibiotics, they are widely distributed in the environment. Long-term exposure to multiple antibiotics may occur in humans through medication and dietary intake. Therefore, it is critical to estimate daily intake and health risk of antibiotics based on urinary biomonitoring. This review compares the strengths and weaknesses of current analytical methods to determine antibiotics in urine samples, discusses the urinary concentration profiles and hazard quotients of individual antibiotics, and overviews correlations of antibiotic exposure with the risk of diseases. Liquid chromatography-tandem mass spectrometry is most applied to simultaneously determine multiple types of antibiotics at trace levels. Solid-phase extraction with a hydrophilic-lipophilic balance adsorbent is commonly used to extract antibiotics in urine samples. Fifteen major antibiotics with relatively higher detection frequencies and concentrations include sulfaclozine, trimethoprim, erythromycin, azithromycin, penicillin V, amoxicillin, oxytetracycline, chlortetracycline, tetracycline, doxycycline, ofloxacin, enrofloxacin, ciprofloxacin, norfloxacin, and florfenicol. Humans can be easily at microbiological effect-based risk induced by florfenicol, ciprofloxacin, azithromycin, and amoxicillin. Positive associations were observed between specific antibiotic exposure and obesity, allergic diseases, and mental disorders. Overall, the accessible, automated, and environmentally friendly methods are prospected for simultaneous determinations of antibiotics at trace level in urine. To estimate human exposure to antibiotics more accurately, knowledge gaps need to be filled up, including the transformation between parent and metabolic antibiotics, urinary excretion proportions of antibiotics at low-dose exposure and pharmacokinetic data of antibiotics in humans, and the repeated sampling over a long period in future research is needed. Longitudinal studies about antibiotic exposure and the risk of diseases in different developmental windows as well as in-depth research on the pathogenic mechanism of long-term, low-dose, and joint antibiotic exposure are warranted.

Polynuclear ruthenium organometallic complexes containing a 1,3,5-triazine ligand: synthesis, DNA interaction, and biological activity

It is now well established that ruthenium complexes are attractive alternatives to platinum-based anticancer agents. Most of the ruthenium compounds currently under investigation contain a single metal center. The synthesis of multinuclear analogues may provide access to novel complexes with enhanced biological activity. In this work, we have synthesized a set of three trinuclear complexes containing organometallic ruthenium fragments-(arene)RuCl-coordinated to a 2,4,6-tris(di-2-pyridylamino)-1,3,5-triazine core [(Arene = benzene (2), p-cymene (1), or hexamethylbenzene (3)]. The interaction of the complexes with DNA was extensively studied using a variety of biophysical probes as well as by molecular docking. The complexes bind strongly to DNA with apparent binding constants ranging from 2.20 to 4.79 × 10⁴ M^-1. The binding constants from electronic absorption titrations were an order of magnitude greater. The mode of binding to the nucleic acid was not definitively determined, but the evidence pointed to some kind of non-specific electrostatic interaction. None of the complexes displayed any significant antimicrobial activity against the organisms that were studied and exhibited anticancer activity only at high (> 100 μM) concentration.

Selective Electrochemical Detection of Ciprofloxacin with a Porous Nafion/Multiwalled Carbon Nanotube Composite Film Electrode

This study focuses on the development of electrochemical sensors for the detection of Ciprofloxacin (CFX) in natural waters and wastewater effluents. The sensors are prepared by depositing a layer of multiwalled carbon nanotubes (MWCNTs) dispersed in a porous Nafion film on to a boron-doped diamond (BDD) electrode substrate. The porous-Nafion-MWCNT/BDD electrode enhanced detection of CFX due to selective adsorption, which was accomplished by a combination of electrostatic attraction at -SO3(-) sites in the porous Nafion film and the formation of charge assisted hydrogen bonding between CFX and -COOH MWCNT surface functional groups. By contrast, the bare BDD electrode did not show any activity for CFX oxidation. The sensors were selective for CFX detection in the presence of other antibiotics (i.e., amoxicillin) and other nontarget water constituents (i.e., Cl(-), Ca(2+), humic acid, sodium dodecylbenzenesulfonate, salicylic acid, 4-aminobenzoic acid, and 4-hydroxybenzoic acid). A limit of detection of 5 nM (S/N = 5.04 ± 0.26) in a 0.1 M KH2PO4 supporting electrolyte (pH = 4.5) was obtained using differential pulse voltammetry. The linear dynamic ranges with respect to CFX concentration were 0.005-0.05 μM and 0.05-10 μM, and the sensitivities were 41 ± 5.2 μA μM(-1) and 2.1 ± 0.22 μA μM(-1), respectively. Sensor fouling was observed at high concentrations of some organic compounds such as 1 mM 4-aminobenzoic acid and 4-hydroxybenzoic acid. However, a short cathodic treatment fully restores sensor response. The results indicate that these sensors have application in detecting CFX in natural waters and wastewater effluents.

DNA binding studies of hematoxylin-Dy(ш) complex by spectrometry using acridine orange as a probe

The interaction of a hematoxylin(HE)-Dy(Ш) complex with herring sperm DNA(hsDNA) was studied using acridine orange(AO) as a probe by UV-vis absorption, circular dichroism(CD), fluorescence spectroscopy and viscosity measurements. From the results of the probe experiment, we found that the HE-Dy(Ш) complex could compete with AO for intercalating into hsDNA. The binding constants of the HE-Dy(Ш) complex to hsDNA was obtained by the double reciprocal method and indicated that the affinity between hsDNA and the complex is weaker than that between hsDNA and classical intercalators. The thermodynamic parameters(ΔH°, ΔG°, ΔS°) were calculated from the UV-vis absorption data measured at two different temperatures. Further experimental results suggested that there exist groove binding and partial intercalation binding between hsDNA and HE-Dy(Ш) complex.

Exploration of Electrochemical Intermediates of the Anticancer Drug Doxorubicin Hydrochloride Using Cyclic Voltammetry and Simulation Studies with an Evaluation for Its Interaction with DNA

Electrochemical behavior of the anticancer drug doxorubicin hydrochloride was studied using cyclic voltammetry in aqueous medium using Hepes buffer (pH~7.4). At this pH, doxorubicin hydrochloride undergoes a reversible two-electron reduction withE1/2value −665±5 mV (versus Ag/AgCl, saturated KCl). Depending on scan rates, processes were either quasireversible (at low scan rates) or near perfect reversible (at high scan rates). This difference in behavior of doxorubicin hydrochloride with scan rate studied over the same potential range speaks of differences in electron transfer processes in doxorubicin hydrochloride. Attempt was made to identify and understand the species involved using simulation. The information obtained was used to study the interaction of doxorubicin hydrochloride with calf thymus DNA. Cathodic peak current gradually decreased as more calf thymus DNA was added. The decrease in cathodic peak current was used to estimate the interaction of the drug with calf thymus DNA. Nonlinear curve fit analysis was applied to evaluate the intrinsic binding constant and site size of interaction that was compared with previous results on doxorubicin hydrochloride-DNA interaction monitored by cyclic voltammetry or spectroscopic techniques.

Interaction of antitumor flavonoids with dsDNA in the absence and presence of Cu(II)

The binding of antitumor flavonoids, namely 3-hydroxyflavone (3HF) and hesperidin (Hesp) with dsDNA was investigated in the absence and presence of Cu(II) using cyclic voltammetry and square wave voltammetry at the hanging mercury drop electrode. The reduction currents of 3HF, 3HF-Cu complex, and the 3HF-β-cyclodextrin inclusion complex decreased after intercalation into dsDNA. The intercalation of Hesp into dsDNA is weak. dsDNA is reduced at a potential of -1.48 V overlaying the reduction of Hesp. In contrast, in the presence of Cu(II), the interaction of Hesp with dsDNA leads to a much stronger intercalation. The binding constants of the flavonoid-Cu complex with dsDNA were evaluated and calibration graphs for the determination of dsDNA were obtained from the decrease in the peak current in the cyclic voltammograms of 3HF in the presence of dsDNA. The proposed method exhibited good recovery and reproducibility for indirect determination of dsDNA.

Interaction of Calf Thymus DNA with the Ni(II) Complex of Sodium 1,4-Dihydroxy-9,10-Anthraquinone-2-Sulphonate: A Novel Method of Analysis Using Cyclic Voltammetry

Hydroxy-9,10-anthraquinones are cheaper alternatives to anthracycline drugs. They closely resemble anthracycline drugs both from a structural and functional viewpoint. Electrochemical behavior of the Ni(II) complex (Na2[Ni(NaLH)2Cl2]⋅2H2O) of sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulphonate (NaLH2), analogue of the core unit of anthracycline anticancer drugs, was studied at physiological pH using cyclic voltammetry. The Ni(II) complex of sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulphonate undergoes diffusion-controlled one-electron reduction that enables performing an electrochemical study on the interaction of the complex with calf thymus DNA. The complex was titrated with increasing concentrations of DNA, and the reduction peak for the unbound complex helped in evaluating binding parameters. Analysis of binding data using nonlinear curve fit in a cyclic voltammetry experiment is the first such attempt. The paper evaluates site size of interaction that also serves as a means to determine stoichiometry of complex formation, between a metal ion and ligand from a DNA interaction study, probably a first of its kind.

Spectroscopic studies on the binding of a new quinolone antibacterial agent: sinafloxacin to DNA

The binding of sinafloxacin to DNA has been studied by fluorescence spectroscopy and UV-vis absorption spectroscopy. The variations in the spectroscopic characteristics of sinafloxacin upon addition of DNA were observed. Salt concentration effect, KI quenching, fluorescence polarization, DNA denaturation experiments, melting temperature (T(m)) curves and viscosity measurements were studied to investigate the binding mechanism. It was proved that the fluorescence quenching of sinafloxacin is a result of the formation of sinafloxacin-DNA complex. Quenching constants were determined using the Stern-Volmer equation. From the experiment evidence, the major binding mode of sinafloxacin with DNA was evaluated to be the groove binding.

Sensitive voltammetric detection of yeast RNA based on its interaction with Victoria Blue B

Voltammetric studies of the interaction of yeast RNA (y-RNA) with Victoria Blue B (VBB) are described in this paper. Furthermore, a linear sweep voltammetric method for the detection of y-RNA was established. The reaction conditions, such as acidity and amount of buffer solution, the concentration of VBB, the reaction time and temperature, etc., were carefully investigated by second order derivative linear sweep voltammetry. Under the optimal conditions, the reduction peak current of VBB at -0.75V decreased greatly after the addition of y-RNA to the solution without any shift of the reduction peak potential. Based on the decrease of the peak current, a new quantitative method for the determination of y-RNA was developed. The effects of co-existing substances on the determination were carefully investigated and three synthetic samples were determined with satisfactory results. The stoichiometry of the VBB-y-RNA complex was calculated by linear sweep voltammetry and the interaction mechanism is discussed.

Voltammetric and spectroscopic studies on binding of antitumor Morin, Morin-Cu complex and Morin-beta-cyclodextrin with DNA

A systematic comparative study of the binding of antitumor Morin and its complexes with DNA has been investigated in the Britton-Robison (BR) buffer solutions using voltammetric and spectroscopic methods. The results show that Morin molecule, acting as an intercalator, is inserted into the cavity of the beta-cyclodextrin (beta-CD) as well as into the base stacking domain of the DNA double helix. The interaction of Morin-Cu complex or the inclusion complex of Morin-beta-CD with ds-DNA causes hypochromism in the absorption spectra, along with pronounced changes in the electrochemical behavior of the Morin complexes. An isobestic point and a new spectrum band appeared indicating the formation of the new system of Morin-Cu-DNA at lambda(m)=391 nm and Morin-beta-CD-DNA at lambda(m)=375 nm. The intercalation of Morin-Cu and Morin-beta-CD complexes with DNA produces an electrochemically inactive supramolecular complex. The binding constants were calculated from the increase of the solubility, the strong hypochromism, and the decrease in peak current of Morin and its complexes upon the addition of the host molecules. Calculation of the thermodynamic parameters of the interaction of the inclusion complex of Morin-beta-CD with DNA, including Gibbs free energy change, Helmholz free energy and entropy change shows that the complexation is a spontaneous process of association.

Interaction of anticancer herbal drug berberine with DNA immobilized on the glassy carbon electrode

The interaction of anticancer herbal drug berberine with double-strand DNA (dsDNA) and single-strand DNA (ssDNA) in solution, dsDNA immobilized on the glassy carbon electrode prepared by Langmuir-Blodgett technique, were investigated by electrochemical techniques (cyclic voltammetry, differential pulse voltammetry) and UV spectroscopy. The presence of DNA results in a decrease of the currents and a negative shift of the electrode potentials from the DPV curves of berberine, indicating the dominance of electrostatic interactions. The spectroscopy data confirmed that the predominant interaction between berberine and DNA is electrostatic. The binding of berberine with DNA, when analyzed in terms of the cooperative Hill model, yields the binding constant K(a)=2.2(+/-0.2)x10(4) M(-1), corresponding to the dissociation equilibrium constant K(d)=4.6(+/-0.3)x10(-5) M, which in the range of the applied concentrations of DNA (bp) and berberine, and a Hill coefficient m=1.82(+/-0.08) in Britton-Robinson buffer solution (0.05 M, pH 5.72) at T=298 K (25 degrees C). Apparently, at least two molecules of berberine have to bind as a couple to cause, e.g., the "elementary event" of current change. The results are suggestive for further fruitful applications of this anticancer herbal drug and DNA-modified electrodes.

Study on the interaction mechanism between DNA and the main active components in Scutellaria baicalensis Georgi

Binding of baicalein, wogonin and baicalin to fish sperm DNA was studied by using ethidium bromide dye as a fluorescence probe. To study the binding mechanism, the absorption, fluorescence, melting temperature and viscosity measurement were carried out. The experimental results indicated that the planar of flavonoids intercalated to the DNA helix. When bound to DNA, flavonoids showed hyperchromic and blue shift in the absorption spectra and fluorescence quenching (>50%) in the fluorescence spectra. Furthermore, the intercalative binding was consistent with the red shift in the position of λ _max in the fluorescence spectra. It was also found that ionic strength had little or no effect on the binding of flavonoids and DNA. Stern-Volmer plots at 25 and 37 °C showed that the quenching of fluorescence by flavonoids was a combined quenching process. The binding site number n, apparent binding constant K _A at 25 and 37 °C, and the corresponding thermodynamic parameters ΔG, ΔH, ΔS at 25 °C were obtained. The interaction of flavonoid-metal complexes with DNA was also studied by spectral methods, and the results suggested that the complexes intercalated into DNA.

Surface plasmon resonance biosensor for enrofloxacin based on deoxyribonucleic acid

A DNA-based surface plasmon resonance biosensor for enrofloxacin was developed. Heating denatured DNA immobilized on the gold-coated glass surface was exploited. The immobilization was performed by a layer-by-layer co-deposition with a cationic polymer. The sensor performance was tested with real biological probes. Direct and simple determination of enrofloxacin in milk samples was demonstrated. The sensor response obeys Langmuir binding isotherm being almost linear until about 20 microg mL(-1). The detection limit in milk samples was estimated to be 3 microg mL(-1).