RESEARCH PAPER An aptamer-based biosensor for detection of doxorubicin by electrochemical impedance spectroscopy Nicole Bahner 1 & Peggy Reich 1 & Dieter Frense 1 & Marcus Menger 2 & Katharina Schieke 1 & Dieter Beckmann 1 Received: 31 August 2017 /Revised: 31 October 2017 /Accepted: 24 November 2017 # Springer-Verlag GmbH Germany, part of Springer Nature 2017 Abstract An aptamer-based biosensor was developed for the detection of doxorubicin using electrochemical impedance spectroscopy. Doxorubicin and its 14-dehydroxylated version daunorubicin are anthracyclines often used in cancer treatment. Due to their mutagenic and cardiotoxic effects, detection in groundwater is desirable. We developed a biosensor using the daunorubicin- binding aptamer as biological recognition element. The aptamer was successfully co-immobilized with mercaptohexanol on gold and a density of 1.3*10 13 ± 2.4*10 12 aptamer molecules per cm 2 was achieved. The binding of doxorubicin to the immobilized aptamer was detected by electrochemical impedance spectroscopy. The principle is based on the inhibition of electron transfer between electrode and ferro-/ferricyanide in solution caused by the binding of doxorubicin to the immobilized aptamer. A linear relationship between the charge transfer resistance (R ct ) and the doxorubicin concentration was obtained over the range of 31 nM to 125 nM doxorubicin, with an apparent binding constant of 64 nM and a detection limit of 28 nM. With the advantages of high sensitivity, selectivity, and simple sensor construction, this method shows a high potential of impedimetric aptasensors in environmental monitoring. Keywords Aptasensor . Faradaic EIS . Electroanalytical methods . Water pollution . Self-assembly Introduction Doxorubicin and its 14-dehydroxylated version daunorubicin belong to the group of anthracycline antibiotics and are used as chemotherapeutic agents in cancer therapy [1]. Animal ex- periments have shown that doxorubicin is mutagenic, cardio- and embryotoxic. The median lethal dose LD 50 of doxorubi- cin if administered orally is for mice 205 mg/kg and for rats 336 mg/kg. For humans the lowest lethal dose known if ad- ministered orally is 6 mg/kg [2]. Due to its toxic effect on proliferating cells, strong side effects such as hair loss, vomiting, bone marrow depression, and cardiotoxicity can occur during chemotherapy [3]. During medical treatment, this drug reaches the sewage system. Mahnik et al. investigat- ed the sewage of an oncological station at Vienna General Hospital over a period of 2 y and detected doxorubicin in the range from 0.48 to 2.48 nM [4]. Owing to incomplete degradation in sewage treatment plant, it gets into the ground- and drinking water. It contaminates nature and endan- gers humans and the environment in high concentrations be- cause of its cardiotoxicity. So far, the detection of doxorubicin has been carried out using various classic analytical methods such as gas chroma- tography [5, 6], liquid chromatography [7], high-performance liquid chromatography [8, 9], UV-Vis spectroscopy [10], fluo- rescence spectroscopy [11, 12], and capillary electrophoresis [13, 14]. Using these classic methods, concentrations in the nanomolar range could be detected (down to 1 nM). However, these methods require a high instrumental effort and can only be handled by qualified people. Erdem et al. developed a voltammetric and impedimetric graphite sensor against dau- norubicin based on dendrimers and was able to reach a detec- tion limit of 128 nM [15]. An alternative to dendrimers as biological recognition ele- ment are aptamers. These play an increasingly important role Parts of this work were presented at the First European / 10th German BioSensor Symposium, Potsdam, 2017. * Nicole Bahner N.Bahner@hs-mannheim.de 1 Institute for Bioprocess and Analytical Measurement Technology e.V. Rosenhof, 37308 Heilbad Heiligenstadt, Germany 2 Fraunhofer Institute for Cell Therapy and Immunology, Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476 Potsdam, Germany Analytical and Bioanalytical Chemistry https://doi.org/10.1007/s00216-017-0786-8