The First Electrochemical MIP Sensor for Tamoxifen

Aysu Yarman,Frieder Scheller

doi:10.3390/s140507647

Aysu Yarman, Frieder Scheller

Open Access

https://doi.org/10.3390/s140507647

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Abstract

We present an electrochemical MIP sensor for tamoxifen (TAM)—a nonsteroidal anti-estrogen—which is based on the electropolymerisation of an O-phenylenediamine–resorcinol mixture directly on the electrode surface in the presence of the template molecule. Up to now only “bulk” MIPs for TAM have been described in literature, which are applied for separation in chromatography columns. Electro-polymerisation of the monomers in the presence of TAM generated a film which completely suppressed the reduction of ferricyanide. Removal of the template gave a markedly increased ferricyanide signal, which was again suppressed after rebinding as expected for filling of the cavities by target binding. The decrease of the ferricyanide peak of the MIP electrode depended linearly on the TAM concentration between 1 and 100 nM. The TAM-imprinted electrode showed a 2.3 times higher recognition of the template molecule itself as compared to its metabolite 4-hydroxytamoxifen and no cross-reactivity with the anticancer drug doxorubucin was found. Measurements at +1.1 V caused a fouling of the electrode surface, whilst pretreatment of TAM with peroxide in presence of HRP generated an oxidation product which was reducible at 0 mV, thus circumventing the polymer formation and electrochemical interferences.

Highlights

During natural evolution highly competent biocatalysts and binders have evolved from very simple components
A glassy carbon disk electrode (GCE) with a diameter of 3 mm was used as the working electrode, an Ag/AgCl electrode was the reference electrode, and a platinum wire served as the counter electrode
The grounded bulk polymers were packed in chromatography columns and applied for solid phase extraction before HPLC-UV analysis of tamoxifen containing urine samples [11].The imprinting factor, i.e., the ratio of target binding to molecularly imprinted polymers (MIPs) and the non-imprinted control increased from 0.6 for pure acetonitrile up to 7.1 in a ACN/acetic acid mixture

Summary

Introduction

During natural evolution highly competent biocatalysts and binders have evolved from very simple components. Bulk polymerisation is most frequently used for the preparation of molecularly imprinted polymers (MIPs) Their synthesis and application frequently requires the presence of non-aqueous solvents and they frequently show slow target binding due to the restricted transport in the bulk phase. In this paper we present preliminary results of an electrochemical MIP sensor for tamoxifen—a nonsteroidal anti-estrogen which is used in the therapy of invasive human breast cancer (Figure 1). It has been banned by the International Olympic Committee and the indication of metabolites in urine is considered a proof of doping. A concept is discussed for the combination of the respective MIP with the enzymatic conversion of the drug in order to decrease the influence of interfering substances

Chemicals

Preparation of Electrodes

Apparatus and Electrochemical Measurements

Generation of the MIPs and Characterisation with a Redox Marker

Anodic Oxidation of TAM at the MIP Covered Electrode

Conclusions and Outlook