Gold nanoparticles anchored graphitized carbon nanofibers ionic liquid electrode for ultrasensitive and selective electrochemical sensing of anticancer drug irinotecan.

An electrochemical sensor is described for highly sensitive and selective determination of anticancer drug irinitecan (IRT). Gold nanoparticles anchored graphitized carbon nanofibers (Au@GCNFs) was prepared. Au@GCNFs was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray. The combination of high catalytic activity of the nanocomposite Au@GCNFs and the good conductivity ionic liquid [BMIM]PF6 (IL) resulted in a modified paste electrode (IL/Au@GCNFs-PE). The IL/Au@GCNFs-PE exhibits excellent electrocatalytic activity for selective determination of IRT in the presence of physiological electroactive species, such as ascorbic acid (AA), dopamine (DA), uric acid (UA), and caffeine (CAF) mixture, typically at working potential of 0.88 V vs. Ag/AgCl. The linear response ranges 4.0 nM-1.79 µM and 4.5 nM-1.57 µM with limits of detection of 1.55 nM and 1.70 nM were calculated for IRT in the absence and presence of the quaternary mixture, respectively. The sensor is reproducible and stable over four weeks, and interference by biologically essential compounds is negligible. The method was applied to the determination of IRT in pharmaceutical formulations, in spiked blood serum and urine, and in clinical patient blood. The recovery values ranged from 96.0 to 104.2%. Graphical abstract The combination of high catalytic activity of the new nanocomposite AuNPs@GCNFs with the good conductivity ionic liquid (IL) resulted to a modified paste electrode (IL/Au@GCNFs-PE). The novel sensor was successfully applied for the sensitive and selective detection of IRT in biological samples in the presence of quaternary ascorbic acid (AA), dopamine (DA), uric acid (UA), and caffeine (CAF) mixture.

Synergistic electrocatalytic activity of In2O3@FMWCNTs nanocomposite for electrochemical quantification of dobutamine in clinical patient blood and in injection dosage form.

Dobutamine (DBT) is a sympathomimetic amine drug that was designed as an inotropic agent for use in congestive heart failure. Hence, there was an impetus to develop a rapid and accurate method for monitoring the concentration of DBT within clinical samples. To address this critical need, a novel In2O3 and functionalized multi-walled carbon nanotubes nanocomposite (In2O3@FMWCNTs) was successfully prepared and applied in an electrochemical sensor to detect DBT. The resulting sensor displayed electrocatalytic toward the oxidation of DBT, which attributed to the synergistic effect of In2O3 and FMWCNTs. Electrochemical impedance spectroscopy (EIS) studies revealed that the smaller charge transfer resistance value (Rct) was observed at In2O3@FMWCNTs modified glassy carbon spherical (GCS) paste electrode (PE) as compared to that of In2O3NPs/GCSPE, FMWCNTs/GCSPE and GCSPE, which authenticates its good conductivity. Furthermore, the calculated value of standard rate constant (ks) for the modified electrode demonstrates the fast electron transfer between DBT and the electrode surface. The fabricated electrochemical sensor indicated high selectivity and sensitivity for DBT determination over the oxidation of uric acid and ascorbic acid. The limit of detection of DBT at In2O3@FMWCNTs/GCSPE was found to be 1.42 × 10-10 M. The proposed sensor is effectively used for the detection of DBT in biological fluids, clinical patient blood and in injection dosage form.

A novel megestrol acetate electrochemical sensor based on conducting functionalized acetylene black-CeO2NPs nanohybrids decorated glassy carbon microspheres.

For the first time, megestrol acetate (MGA), a synthetic progestin with therapeutic use in breast cancer, is electrochemically studied to propose a new electroanalytical alternative for its detection in real samples. In the present work, a novel electrochemical sensor based on functionalized acetylene black-CeO2NPs nanohybrids modified glassy carbon microspheres paste electrode (FAB-CeO2NPs/GCMPE) was successfully fabricated and used for sensitive determination of MGA. The modified electrode has been characterized using scanning electron microscope (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrocatalytic reduction of MGA using FAB-CeO2NPs/GCMPE was carried out via CV and square wave voltammetry (SWV). By employing FAB-CeO2NPs/GCMPE, the SWV signal of MGA reduction was 8 fold higher than the bare GCMPE. A wide concentration range from 4.20 × 10-8 to 1.13 × 10-6 M with the low LOD of 1.30 nM for MGA was achieved. The practical analytical utilities of the prospective FAB-CeO2NPs/GCMPE sensor were demonstrated successfully by the detection of MGA in Megace tablets, human serum and urine samples obtained from healthy and patient volunteers after oral administration of 160 mg Megace tablets. HPLC method was also developed for comparison with the electroanalytical method.

A novel sensor based on nanobiocomposite Au--In2O3--chitosan modified acetylene black paste electrode for sensitive detection of antimycotic ciclopirox 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.

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 ΔG o, ΔH o and ΔS o 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.

Interactions of an anticancer drug Formestane with single and double stranded DNA at physiological conditions.

Mode of interactions of anticancer drug Formestane (FMT) with single and double stranded DNA has been investigated at different temperatures and at two physiological pH values i.e. 7.4 (human blood pH) and 4.7 (stomach pH). Fluorescence spectroscopy, UV-Vis spectroscopy, cyclic voltammetry and square wave voltammetry were employed to probe the interaction between FMT and DNA. The observed fluorescence quenching of dsDNA-ethidium bromide system by the anticancer drug FMT confirmed the intercalative mode of binding between the FMT and dsDNA. The absorption spectra and voltammetric results indicate FMT gets intercalated between dsDNA bases and the strength of interaction is independent on the ionic strength. Comparison of the mode of interaction of FMT with dsDNA and ssDNA was discussed. The calculated binding constants for FMT-dsDNA and FMT-ssDNA complexes at pH 7.4 were found to be 1.52×10(5)M(-1) and 1.24×10(6)M(-1), respectively. Stoichiometric coefficients and thermodynamic parameters of FMT-dsDNA and FMT-ssDNA complexes were evaluated. The association between the anticancer drug FMT with DNA is maximum at pH 7.4 which depicts the most stable complexes are formed at human blood pH. The decrease in peak current of FMT resulting from its interaction with DNA was employed for determination of dsDNA and ssDNA concentration at physiological conditions.

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.

Differential pulse polarographic determination of poly(8-hydroxyquinoline) in the presence and absence of an insulating poly(vinyl alcohol) matrix.

The electrochemical activity of poly(8-hydroxyquinoline) (PHQ) in acid and alkaline media has been investigated by use of differential pulse polarography (DPP). The reduction peak height (I(p)) of PHQ in universal buffer solutions is not useful as an analytical signal, because it is highly affected by hydrogen evolution in acid media and appears as a small peak located at more negative potential values in alkaline media. A new and highly sensitive reduction peak (E(p)=-0.45, pH 9.25) appears, however, after addition of trace amounts of PHQ to Cu(II), or vice versa. This reduction peak is a result of the reduction of Cu(II) chelates in the PHQ-Cu(II) complex and is highly promising for the trace determination of PHQ at nanomolar and submicromolar levels. The response current (I(p)/mu A) for the reduction peak of Cu(II) chelates in a PHQ-Cu(II) matrix results in sensitivity to the concentration of PHQ at least three orders of magnitude higher than that for the reduction peak of PHQ alone under the same conditions. The limit of detection is as low as 5.264 ppb (microg L(-1)). The effect of a variety of anions and cations and of an insulating poly(vinyl alcohol) (PVA) matrix has been investigated. Electroactive PHQ-Cu(II) at a level of 0.685% could induce a current of approximately 240 nA in an insulating PVA matrix, suggesting possible application for the preparation of a PHQ-Cu(II)-PVA electroactive composite.