Electrochemical and theoretical study on interaction between erlotinib and DNA.

A comprehensive investigation of tyrosine kinase inhibitor erlotinib (ERL) electrochemical behavior and interaction with DNA was performed with the aim to clarify its redox mechanism and to determine the mode of binding. Irreversible oxidation and reduction processes of ERL on glassy carbon electrode were investigated using three voltammetric techniques CV, DPV, SWV in pH range between 2.0 and 9.0. Oxidation was established as an adsorption-controlled process, while the reduction manifested diffusion-adsorption mixed controlled process in acidic medium and adsorption became predominant in the neutral solutions. According to the determined number of transferred electrons and protons, oxidation and reduction mechanism of ERL are proposed. To follow the interaction between ERL and DNA, the multilayer ct-DNA electrochemical biosensor was incubated in ERL solutions concentrations ranged from 2 × 10-7 M to 5 × 10-5 M (pH 4.6) for 30 min. SWV measurements have shown the decrease in deoxyadenosine peak current as a consequence of ERL increased concentration and binding to ct-DNA. The calculated value of binding constant was K = 8.25 × 104 M-1. Molecular docking showed that ERL forms hydrophobic interactions when docked into minor groove, as well as when intercalated, and molecular dynamics analysis predicted the stability of obtained complexes. These results together with voltammetric studies imply that the intercalation could be more dominant way ERL binding to DNA compared to minor groove binding.

Electrochemical Characterisation and Confirmation of Antioxidative Properties of Ivermectin in Biological Medium.

Ivermectin (IVM) is a drug from the group of anthelmintics used in veterinary and human medicine. Recently, interest in IVM has increased as it has been used for the treatment of some malignant diseases, as well as viral infections caused by the Zika virus, HIV-1 and SARS-CoV-2. The electrochemical behaviour of IVM was investigated using cyclic (CV), differential pulse (DPV) and square wave voltammetry (SWV) at glassy carbon electrode (GCE). IVM showed independent oxidation and reduction processes. The effect of pH and scan rate indicated the irreversibility of all processes and confirmed the diffusion character of oxidation and reduction as an adsorption-controlled process. Mechanisms for IVM oxidation at the tetrahydrofuran ring and reduction of the 1,4-diene structure in the IVM molecule are proposed. The redox behaviour of IVM in a biological matrix (human serum pool) showed a pronounced antioxidant potential similar to that of Trolox during short incubation, whereas a prolonged stay among biomolecules and in the presence of an exogenous pro-oxidant (tert-butyl hydroperoxide, TBH) resulted in a loss of its antioxidant effect. The antioxidant potential of IVM was confirmed by voltametric methodology which is proposed for the first time.

Square wave voltammetric study of interaction between 9-acridinyl amino acid derivatives and DNA.

Electrochemical oxidation of newly synthesized acridine derivatives (ADs): PG, PA, EG and EA was studied using square wave voltammetry at a glassy carbon electrode. Oxidation occurs as an irreversible process for all ADs. The ADs interaction with DNA was investigated using multi-layer DNA electrochemical biosensor. The shift of dA peak in positive direction indicated that the type of interaction is most likely an intercalation. PG showed the widest range of concentration capable to interact with DNA (1 × 10-7 M - 2.5 × 10-4 M). Analysing logIcomplexIDNA-IcomplexvslogcAD plots, the binding constants were determined. For the lowest PG concentrations, obtained K value close to 106 M-1 refers to strong binding. The values of K for PA may be classified as medium strength, while EG and EA showed low K values. Our results unequivocally showed that the characteristics of association complexes may vary depending on the concentration of the interacting substance. The negative ΔG value for all ADs, (- 21 to - 34 kJ mol-1), confirms the process spontaneity. The best result, indicating the most stable formed complex with DNA adsorbed at the electrode surface, showed PG when present in low concentration, order of 10-7 M. The intercalation of ADs into DNA was supported by molecular docking analysis.

An electrochemical study of 9-chloroacridine redox behavior and its interaction with double-stranded DNA.

The electrochemical behavior of 9-chloroacridine (9Cl-A), a precursor molecule for synthesis of acridine derivatives with cytostatic activity, is a complex, pH-dependent, diffusion-controlled irreversible process. Oxidation of 9Cl-A initiates with the formation of a cation radical monomer, continues via the formation of a dimer subsequent oxidation to new cation radical. Reduction of 9Cl-A produces radical monomers which are stabilized by dimer formation. The investigation was performed using cyclic, differential pulse and square wave voltammetry at a glassy carbon electrode. The interaction between 9Cl-A and double-stranded DNA (dsDNA) was investigated using a multilayer dsDNA-electrochemical biosensor and 9Cl-A solutions from 1.0×10-7M (the lowest 9Cl-A concentration whose interaction with DNA was possible to detect) up to 1×10-4M. These allowed the binding constant, K=3.45×105M-1 and change in Gibbs free energy of the formed adsorbed complex to be calculated. Complex formation was a spontaneous process proceeding via 9Cl-A intercalation into dsDNA inducing structural changes. The intercalation of 9Cl-A into dsDNA was supported by molecular docking analysis. The combination of simple methodology and the use of biosensors to investigate DNA interactions is a powerful tool to offer insight into aspects of drug design during pharmaceutical development.

An overview of the optical and electrochemical methods for detection of DNA - drug interactions.

A large number of inorganic and organic compounds is able to bind to DNA and form complexes. Among them, drugs are very important, especially chemotherapeutics. This paper presents the overview of DNA structural characteristics and types of interactions (covalent and non-covalent) between DNA molecule and drugs. Covalent binding of the drug is irreversible and leads to complete inhibition of DNA function, what conclusively, causes the cell death. On the other hand, non-covalent binding is reversible and based on the principle of molecular recognition. Special attention is given to elucidation of the specific sites in DNA molecule for drug binding. According to their structural characteristics, drugs that react non-covalently with DNA are mainly intercalators, but also minor and major groove binders. When the complex between drug and DNA is formed, both the drug molecule, as well as DNA, experienced some modifications. This paper presents the overview of the methods used for the study of the interactions between DNA and drugs with the aim of detection and explanation of the resulting changes. For this purpose many spectroscopic methods like UV/VIS, fluorescence, infrared and NMR, polarized light spectroscopies like circular and linear dichroism, and fluorescence anisotropy or resonance is used. The development of the electrochemical DNA biosensors has opened a wide perspective using particularly sensitive and selective electrochemical methods for the detection of specific DNA interactions. The presented results summarize literature data obtained by the mentioned methods. The results are used to confirm the DNA damage, to determine drug binding sites and sequence preference, as well as conformational changes due to drug-DNA interaction.

Application of adsorptive stripping voltammetry for determination of selected methoxyimino cephalosporins in urine samples.

In last two decades different electroanalytical methods are used for sensitive and selective determination of cephalosporins. In this paper the electrochemical behavior of methoxyimino cephalosporins, reduction mechanism and nature of the process at the mercury electrode surface is presented. Special attention is paid to the cephalosporins adsorption at the mercury surface. Based on this phenomenon, the adsorptive stripping methods are established for determination of low concentration of these drugs in urine samples, both in-vitro, and in-vivo conditions. The application of the adsorptive stripping differential pulse voltammetry (AdSDPV) for determination of cefpodoxime proksetile (CP), cefotaxime (CF), desacetylcefotaxime (DCF) and cefetamet (CEF) is summarized. The best sensitivity of determination in-vitro in urine was achieved for CP, in acid solutions (LOD 7.410(-9)M and LOQ 2.410(-8)M), followed by CF, CEF and DCF. This is in accordance with the strength of their adsorption. Determination of CF and DCF by AdSDPV in-vivo is also presented. Compared to other analytical methods, AdSDPV showed advantages in simplicity of the sample preparation, and over the other voltamperometric methods, higher sensitivity and selectivity.

The possibility of simultaneous voltammetric determination of desloratadine and 3-hydroxydesloratadine.

The electrochemical behaviour of desloratadine (DLOR) and its derivative 3-hydroxydesloratadine (3OH-DLOR) was investigated by direct current (DCP) polarography, cyclic (CV), differential pulse (DPV) and square-wave (SWV) voltammetry in Britton-Robinson (BR) buffer solutions (pH 4-11). Both compounds are reduced at mercury electrode in irreversible two electron reduction of the C=N bond of the pyridine ring in their molecules. The difference in their electrochemical behaviour was investigated, and the most pronounced distinction is observed at pH > 9, as a consequence of the deprotonation of the phenolic moiety in 3OH-DLOR molecule, yielding significant change in their reduction potentials (Ep DLOR = -1.48 V, and Ep 3OH-DLOR = -1.6 V). The observed results correlate with calculated LUMO energy levels and Hammet substituent constants (σ). Based on the difference in the reduction potential for DLOR and 3OH-DLOR, conditions for simultaneous determination these two molecules in alkaline medium were established. The best selectivity was achieved using SWV method at pH 10. The linearity of the calibration graphs were achieved in the concentration range from 1.5 × 10-6 M - 1 × 10-5 M for DLOR and 7.5 × 10-6 M - 5 × 10-5 M for 3OH-DLOR with detection limits of 2.29 × 10-7 M and 2.08 × 10-6 M, and determination limits of 7.64 × 10-7 M and 6.94 × 10-6 M, for DLOR and 3OH-DLOR, respectively. The method was checked in human plasma sample. Good response was obtained with LOD and LOQ values of 4.63 × 10-7 M and 1.54 × 10-6 M, for DLOR and 2.39 × 10-6 M and 7.97 × 10-6 M, 3OH-DLOR, respectively.

Simultaneous determination of cefotaxime and desacetylcefotaxime in real urine sample using voltammetric and high-performance liquid chromatographic methods.

Two rapid, accurate and sensitive methods are developed and validated for the quantitative simultaneous determination of cefotaxime (CFX) and its active metabolite desacetylcefotaxime (DCFX) in urine. Based on the previous results which showed the four electron reduction of CFX at approximately -0.5 V, and the new findings that DCFX reduction occurred at more positive potential (-0.23 V), the new adsorptive stripping differential pulse voltammetric (AdSDPV) method was developed for determination of CFX in the presence of DCFX. Linear responses were observed over a wide concentration range (0.07-0.52 microg/ml for CFX and 0.22-1.3 microg/ml for DCFX) in urine. The second assay involves subsequent separation on a reversed-phase HPLC column, with ultraviolet detection at 262 nm. Retention times were 4.057 and 1.960 min for CFX and DCFX, respectively. Linear responses were observed over a wide range, 0.55-6.60 microg/ml for CFX and 1.10-11.00 microg/ml for DCFX, in urine. The statistical evaluation for both methods was examined by means of within-day repeatability (n=5) and day-to-day precision (n=3) and was found to be satisfactory with high accuracy and precision.