Fabrication of an electrochemical sensor based on carbon nanotubes modified with gold nanoparticles for determination of valrubicin as a chemotherapy drug: Valrubicin-DNA interaction

• A sensitive electrochemical sensor has been fabricated for detection of valrubicin base on AuNPs/en/MWCNTs/AuE.
• The constructed sensor has the detection limit of 18 nM towards valrubicin.
• Valrubicin was successfully analyzed in urine and blood samples after simple pretreatment.
• The interaction of valrubicin with DNA was studied by binding oligonucleotides on AuNPs.

In this study, an electrochemical sensor was fabricated based on gold nanoparticles/ ethylenediamine/ multi-wall carbon-nanotubes modified gold electrode (AuNPs/en/MWCNTs/AuE) for determination of valrubicin in biological samples. Valrubicin was effectively accumulated on the surface of AuNPs/en/MWCNTs/AuE and produced a pair of redox peaks at around 0.662 and 0.578 V (vs. Ag/AgCl) in citrate buffer (pH 4.0). The electrochemical parameters including pH, buffer, ionic strength, scan rate and size of AuNPs have been optimized. There was a good linear correlation between cathodic peak current and concentration of valrubicin in the range of 0.5 to 80.0 μmol L− 1 with the detection limit of 0.018 μmol L- 1 in citrate buffer (pH 4.0) and 0.1 mol L- 1 KCl. Finally, the constructed sensor was successfully applied for determination of valrubicin in human urine and blood serum. In further studies, the different sequences of single stranded DNA probes have been immobilized on the surface of AuNPs decorated on MWCNTs to study the interaction of oligonucleotides with valrubicin.