Determination of Azidothymidine – an Antiproliferative and Virostatic Drug by Square‐Wave Voltammetry

Abstract

The 3'-azido-3'-deoxythymidine (AZT, Zidovudine) is an antiproliferative and virostatic drug widely used in human immunodeficiency virus type 1 (HIV-1) infection treatment. With respect to side effects of high doses and a short halflife of AZT, a fast and simple detection method for this agent could be helpful. The aim of our study was to determine AZT levels in natural samples (urine, serum, whole blood, and cell cultures, such as the HaCaT line of keratinocytes) without their mineralization and/or purification, by means of electrochemical methods using hanging mercury drop electrode (HMDE). On this electrode, AZT undergoes irreversible reduction at the peak potential near E p À 1.1 V (vs. Ag/AgCl/3 M KCl). Reduction AZT signals were measured by cyclic voltammetry (CV), differential pulse voltammetry (DPV), square-wave voltammetry (SWV), and constant current chronopotentiometric stripping analysis (CPSA). In phosphate buffer (pH 8) the SWV yielded the best AZT signal with the detection limit of 1 nM. The determination of AZT concentration in biological materials is affected by electroactive components, such as proteins and DNA. For monitoring the influence of these compounds, AZT reduction was performed in the presence of 10 mg/ mL calf thymus ssDNA and/or 100 mg/mL bovine serum albumin. In these cases, the detection limit increased to 0.25 mM. Also studied was the AZT concentration in keratinocyte cells (HaCaT line) during cell cultivation. It has been shown that the SWV may be considered as a useful tool for the determination of AZT concentration in cell cultures, and for monitoring AZT pharmacokinetics.

Voltammetric Determination of Azidothymidine Using Silver Solid Amalgam Electrodes

“…Electroanalytical methods published so far for the determination of AZT are summarized in Table 1. The optimized pulse methods in basic buffers resulted in the lowest detection limits of units of nmol L À1 [23,24]. Higher values were reported for direct determination of AZT in various biological matrices without any purification steps [24].…”

“…Cyclic voltammograms recorded at these electrodes in alkaline media indicate irreversible one-step reduction as previously reported for HMDE [19,24]. With a view to develop an analytical method for the AZT determination in drug dosage form, DPV was selected as common electroanalytical method with preferred sensitivity and selectivity in pharmaceutical analysis [43].…”

“…The optimized pulse methods in basic buffers resulted in the lowest detection limits of units of nmol L À1 [23,24]. Higher values were reported for direct determination of AZT in various biological matrices without any purification steps [24]. All these studies were performed using mercury electrodes enabling easy renewal of electrode surface.…”

The Analytical Applications of Square Wave Voltammetry on Pharmaceutical Analysis

“…Vacek et al [60] developed square wave voltammetry for determination of zidovudine. In phosphate buffer the SWV yielded the best zidovudine signal with the detection limit of 1 nM.…”

A sensor for investigating the interaction between biologically important heavy metals and glutathione

“…For the identification and determination of GSH and other related peptides and proteins electrochemical methods based on the catalytic evolution of hydrogen on mercury electrodes (peak H, Brdicka procedure) have been intensively used (Heyrovský, 2000(Heyrovský, , 2004(Heyrovský, , 2006Kizek et al, 2001;Mader et al, 2001;Brázdová et al 2002;Trnková et al, 2002;Strouhal et al, 2003;Průša et al, 2004aPrůša et al, ,b, 2005Průša et al, , 2006aKukačka et al, 2006). Electrochemical techniques appeared to be very suitable for the design of sensors and biosensors (Billová et al, 2003;Kizek et al, 2003;Vacek et al, 2004a;Adam et al, 2005a,b,c;Potěšil et al, 2005Potěšil et al, , 2006.…”