Hossieny Ibrahim

Binding mode and thermodynamic studies on the interaction of the anticancer drug dacarbazine and dacarbazine-Cu(II) complex with single and double stranded DNA.

The binding mode and thermodynamic characteristics of the anticancer drug dacarbazine (Dac) with double and single stranded DNA were investigated in the absence and presence of Cu(II) using cyclic voltammetry, square wave voltammetry and fluorescence spectroscopy. The interaction of Dac and Dac-Cu(II) complex with dsDNA indicated their intercalation into the base stacking domain of dsDNA double helix and the strength of interaction is independent on the ionic strength. The interaction of Dac with dsDNA in the presence of Cu(II) leads to a much stronger intercalation. The interaction mode of Dac molecules with ssDNA is electrostatic attraction via negative phosphate on the exterior of the ssDNA with Dac. The binding constants, stoichiometric coefficients and thermodynamic parameters of Dac and Dac-Cu(II) complex with dsDNA and ssDNA were evaluated. Comparison of the mode interaction of Dac with dsDNA and ssDNA was discussed. The decrease of peak current of Dac was proportional to DNA concentration, which was applied for determination of dsDNA and ssDNA concentration.

Square wave adsorptive stripping voltammetric determination of anticancer drug nilutamide in biological fluids using cationic surfactant cetyltrimethylammonium bromide

A sensitive square wave adsorptive stripping voltammetric method was described for the determination of anticancer drug nilutamide (NLM) in biological fluids based on the enhancement effect of the cationic surfactant: cetyltrimethylammonium bromide (CTAB). With pH 6.0 Britton–Robinson (BR) buffer as the supporting electrolyte and in the presence of 1.45 × 10−4 mol L−1 CTAB, NLM yields a well-defined and sensitive reduction peak at the ZnO nanoparticle modified carbon paste electrode (ZnONPs/CPE). Various chemical and instrumental parameters affecting the monitored electroanalytical response were investigated and optimized for NLM determination. The electrochemical parameters such as the surface concentration (Γ), electron transfer coefficient (α) and standard rate constant (ks) of NLM at the modified electrode were calculated. The achieved limits of detection and quantification were 3.21 × 10−9 mol L−1 and 1.07 × 10−8 mol L−1 by square wave adsorptive stripping voltammetry (SWAdSV), respectively. The proposed method was successfully applied for the detection of NLM in blood and urine samples with good accuracy and precision.

Electrochemical sensor for individual and simultaneous determination of guanine and adenine in biological fluids and in DNA based on a nano-In–ceria modified glassy carbon paste electrode

A novel, simple and sensitive electrochemical method for individual and simultaneous determination and direct electro-oxidation behaviors of guanine (G) and adenine (A) was developed using an In doped ceria nanoparticle modified glassy carbon paste electrode (In–CeO2/GCPE). Scanning electron microscopy (SEM) and electrochemical techniques were employed for characterization of the fabricated modified electrode. The electrochemical sensor exhibits a potent and persistent electro-oxidation behavior followed by well-separated oxidation peaks toward G and A. Electrochemical performances related to the electro-oxidation of G and A at the nano-In–CeO2NPs/GCPE were investigated, showing that their peak currents were greatly enhanced due to the catalytic effect of In doped ceria. The prepared In–CeO2NPs/GCPE showed high selectivity and sensitivity for G and A oxidation over uric acid (UA). A linear range of 0.07–34 μM with a detection limit of 1.19 × 10−8 M for G and 1.96–88.2 μM with a detection limit of 2.86 × 10−8 M for A were achieved. The proposed sensor was used for individual and simultaneous determination of G and A in biological fluids and in ssDNA samples. The value of (G + C)/(A + T) in DNA was calculated to be 0.75.

Individual and simultaneous square wave voltammetric determination of the anticancer drugs emodin and irinotecan at renewable pencil graphite electrodes

A rapid sensitive and versatile method for the individual and simultaneous determination of the anticancer drugs emodin (Em) and irinotecan (Irino) in biological fluids based on the square wave voltammetry (SWV) using a renewable pencil graphite electrode (PGE) was investigated. Controlled adsorptive accumulation of both Em and Irino on the PGE surface was exploited for trace determination of the anticancer drugs in biological fluids. Under the optimized experimental conditions such as supporting electrolyte pH, accumulation potential and time and electrochemical parameters, calibration curves for trace assay of Em and Irino individually and simultaneously showed an excellent linear response. Limits of detection of 5.17 × 10-10 and 1.68 × 10-9 mol L-1 Em and Irino in bulk form were achieved using SWV at a PGE, respectively. The obtained results showed good stability, reproducibility, repeatability and high recovery to assay of two drugs in biological fluids. The statistical analysis and the calibration curve data for trace determination of Em and Irino individually as well as simultaneously are reported.

A novel sensor based on nanobiocomposite Au­In2O3 ­chitosan modified acetylene black paste electrode for sensitive detection of antimycoticciclopirox olamine

For the first time, a sensitive conductive nanobiocomposite sensor consisting of Au-In2O3 nanocomposite and chitosan (CS) was successfully prepared and used for the modification of acetylene black paste electrode (Au--In2O3--CS/ABPE). The phase structures, composition and morphology of Au-In2O3 nanocomposite were characterized by X-ray diffraction (XRD), energy-dispersed X-ray (EDX) and transmission electron microscopy (TEM). Electrochemical activities and surface analysis of the biosensor electrode Au--In2O3--CS/ABPE were investigated using scanning electron microscopy (SEM), cyclic voltammetry and square wave voltammetry. The modified electrode showed an excellent electrochemical activity toward the electro-oxidation of the antimycotic ciclopirox olamine (CPX) leading to a significant improvement in sensitivity as compared to the bare ABPE. The proposed biosensor demonstrated linearity in the range 0.199 - 16.22µmolL-1, with high sensitivity (64.57μAµmolL-1cm-2) and detection limit of 6.64 × 10-9molL-1 CPX. The analytical performance of this biosensor was evaluated for detection of CPX in pharmaceutical formulations with good accuracy and precision. This proposed method was validated by UPLC and the results are in agreement at the 95% confidence level.

Fabrication of a new biosensor based on a Sn doped ceria nanoparticle modified glassy carbon paste electrode for the selective determination of the anticancer drug dacarbazine in pharmaceuticals

A new tin doped ceria nanoparticle modified glassy carbon paste electrode (Sn–CeO2NPs/GCPE) was fabricated for the determination of the anticancer drug dacarbazine (DTIC). The Sn–CeO2 nanoparticles with Sn concentrations from 0 to 10 wt% were synthesized by sol gel method. Sn doped CeO2 nanoparticles were characterized by X-ray diffraction, energy-dispersed X-ray spectrometry (EDS) and transmission electron microscopy (TEM). Cyclic voltammetry (CV) and square wave voltammetry (SWV) were applied to investigate the unique properties of the Sn–CeO2NPs/GCPE. The modified electrode showed an excellent character for electrocatalytic oxidization of DTIC, while the bare GCPE electrode only gave a small oxidation peak. The fabricated sensor showed an excellent anti-interference ability against electroactive species and metal ions. This modified electrode was used as a sensor for determination of DTIC in human biological fluids and in pharmaceutical samples with satisfactory results.

Comparative studies on the interaction of anticancer drug irinotecan with dsDNA and ssDNA

A systematic comparative study on the binding of anticancer drug irinotecan (Irino) with dsDNA and ssDNA was investigated in phosphate buffer solutions using voltammetric and spectroscopic methods. The voltammetric results show that the Irino molecule, acting as an intercalator, is inserted into the base stacking domain of the DNA double helix and the strength of interaction is independent of the ionic strength. The hyperchromic effect observed in the UV-visible spectra of Irino in the presence of dsDNA provided the evidence for the intercalation of the drug chromophore with dsDNA base. The interaction mode of Irino molecules with ssDNA is electrostatic attraction via negative phosphate on the exterior of the ssDNA with Irino. The binding constants, stoichiometric coefficients and thermodynamic parameters of Irino–dsDNA and Irino–ssDNA complexes were evaluated. The magnitude of changes in ΔGo, ΔHo and ΔSo indicated that the binding process of Irino with ssDNA was more affected than that with dsDNA. The decrease of the peak current of Irino was proportional to DNA concentration, which was applied for determination of dsDNA and ssDNA concentration. The achieved limits of detection of dsDNA and ssDNA were 5.49 × 10−7 and 1.87 × 10−7 M, respectively.