Fabrication of an electrochemical sensor for determination of doxorubicin in human plasma and its interaction with DNA

Abstract

In this work, an electrochemical sensor was fabricated for determination of an anthracycline, doxorubicin (DOX) as a chemotherapy drug in plasma based on multi-walled carbon nanotubes modified platinum electrode (Pt/MWCNTs). DOX was effectively accumulated on the surface of modified electrode and generated a pair of redox peaks at around 0.522 and 0.647 V (vs. Ag/AgCl) in Britton Robinson (B-R) buffer (pH 4.0, 0.1 M). The electrochemical parameters including pH, type of buffer, accumulation time, amount of modifier and scan rate were optimized. Under the optimized conditions, there was a linear correlation between cathodic peak current and concentration of DOX in the range of 0.05-4.0 µg/mL with the detection limit of 0.002 µg/mL. The number of electron transfers (n) and electron transfer-coefficient (α) were estimated as 2.0 and 0.25, respectively. The constructed sensor displayed excellent precision, sensitivity, repeatability and selectivity in the determination of doxorubicin in plasma. Moreover, cyclic voltammetry studies of DOX in the presence of DNA showed an intercalation mechanism with binding constant (K_b) of 1.12×10⁵ L/mol.

Keywords: Doxorubicin; Doxorubicin-DNA interaction; Electrochemical sensor; Human plasma; MWCNTs.

Fig. 1

(A) SEM image of pretreated MWCNTs and (B) TEM image of MWCNTs on Pt electrode after drying in oven at 50 °C.

Fig. 2

FTIR spectra of (a) pristine MWCNTs and (b) pretreated MWCNTs with concentrated nitric acid.

Fig. 3

(A) EIS Nyquist plots of bare Pt electrode and Pt/MWCNTs in 1 mM Fe(CN)₆^3−/4− solution containing 0.1 KCl, with frequency of 100 kHz to 0.1 Hz and amplitude of 0.01 V. (B) Cyclic voltammogram of 2.0 µg/mL doxorubicin on (a) bare Pt electrode and (b) Pt/MWCNTs in 0.1 M B-R buffer (pH 4.0) at scan rate of 0.1 V/s.

Fig. 4

(A) The relationship between cathodic peak potential and pH value in 0.1 M B-R buffer in the pH range of 2–4 at scan rate of 0.1 V/s. (B) The effect of kind of buffer on the reduction peak current of 2.0 µg/mL doxorubicin in the presence of 0.1 M of different buffers at pH 4.0. (C) The effect of drop casting volume of MWCNTs on the reduction peak current of doxorubicin in B-R buffer (pH 4.0) at scan rate of 0.1 V/s. (D) Effect of accumulation time on the cyclic voltammogram cathodic peak currents of 2.0 µg/mL doxorubicin in B-R buffer (pH 4.0) solution at scan rate of 0.1 V/s.

Fig. 5

Amperometry study of doxorubicin (100 μg/mL) in 0.1 M B-R buffer (pH 4.0) at applied potential of 0.5 V. Inset: Cottrell plot in the interval time from 1.5 s to 5.0 s.

Fig. 6

Calibration curve for doxorubicin under optimized conditions in the concentration range of 0.2–2.0 and 2.0–4.0 μg/mL. Conditions: 0.1 M B-R buffer (pH 4.0); accumulation time, 80 s; scan rate, 0.1 V/s.

Fig. 7

(A) Cyclic voltammograms of doxorubicin after successive additions of double stranded DNA. C_DNA=0.416, 0.832, 1.248, 1.664, 2.08, 2.496, 2.912, 3.328, 3.744, and 4.16 μM; C_doxorubicin=2 µg/mL, scan rate=0.1 V/s. (B) The variation of reduction peak current for doxorubicin at different concentrations of DNA.