Enzyme-free and label-free strategy for electrochemical oxaliplatin aptasensing by using rGO/MWCNTs loaded with AuPd nanoparticles as signal probes and electro-catalytic enhancers.

An innovative label free electrochemical aptasensor was developed for the analysis of oxaliplatin (OXAL) for the first time. The DNA oligonucleotide (aptamer) was successfully fabricated, by covalently attaching the amino terminus of the functional DNA on the glassy carbon electrode (GCE) surface modified with reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) loaded with AuPd nanoparticles (AuPd NPs@rGO/MWCNTs/GCE). The stepwise assembly process of aptasensor on AuPd NPs@rGO/MWCNTs/GCE was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The aptamer-OXAL complex formation led to inhibition the electron transfer of Fe(CN)63-/4- on the electrode interface, which was clearly observed by decreasing the peak current of the redox probe. Furthermore, we managed to quantitatively measure OXAL by adding different concentrations of OXAL, while monitoring the decrease of differential pulse voltammogram (DPV) responses of the redox probe. Under the optimized conditions, the electrochemical aptasensor exhibited a linear range of 0.1-170.0 nmol L-1 with LOD of 60.0 pmol L-1. Next, we successfully applied the aptasensor calibrated system to determine OXAL in pharmaceutical injection and human biological samples.