Extended-gate field-effect transistor (EG-FET) with molecularly im- printed polymer (MIP) film for selective inosine determination Zofia Iskierko a , Marta Sosnowska a , Piyush Sindhu Sharma a , Tiziana Benincori b , Francis D’Souza c , Izabela Kaminska d , Krzysztof Fronc d , Krzysztof Noworyta a,n a Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland b Dipartimento di Scienza ed Alta Tecnologia, Università degli Studi dell’Insubria, via Valleggio, 11-22100 Como, Italy c Department of Chemistry, University of North Texas, Denton, TX 76203-5017, USA d Institute of Physics, Polish Academy of Sciences, 32/46 Al. Lotników, 02-668 Warsaw, Poland article info Article history: Received 17 April 2015 Received in revised form 12 June 2015 Accepted 27 June 2015 Available online 7 July 2015 Keywords: Extended-gate field-effect transistor Molecularly imprinted polymer Chemosensor Inosine Piezomicrogravimetry abstract A novel recognition unit of chemical sensor for selective determination of the inosine, renal disfunction biomarker, was devised and prepared. For that purpose, inosine-templated molecularly imprinted polymer (MIP) film was deposited on an extended-gate field-effect transistor (EG-FET) signal transducing unit. The MIP film was prepared by electrochemical polymerization of bis(bithiophene) derivatives bearing cytosine and boronic acid substituents, in the presence of the inosine template and a thiophene cross-linker. After MIP film deposition, the template was removed, and was confirmed by UV–visible spectroscopy. Subsequently, the film composition was characterized by spectroscopic techniques, and its morphology and thickness were determined by AFM. The finally MIP film-coated extended-gate field- effect transistor (EG-FET) was used for signal transduction. This combination is not widely studied in the literature, despite the fact that it allows for facile integration of electrodeposited MIP film with FET transducer. The linear dynamic concentration range of the chemosensor was 0.5–50 μM with inosine detect- ability of 0.62 μM. The obtained detectability compares well to the levels of the inosine in body fluids which are in the range 0–2.9 mM for patients with diagnosed diabetic nephropathy, gout or hyperur- icemia, and can reach 25 mM in certain cases. The imprinting factor for inosine, determined from pie- zomicrogravimetric experiments with use of the MIP film-coated quartz crystal resonator, was found to be 5.5. Higher selectivity for inosine with respect to common interferents was also achieved with the present molecularly engineered sensing element. The obtained analytical parameters of the devised chemosensor allow for its use for practical sample measurements. & 2015 Elsevier B.V. All rights reserved. 1. Introduction For several decades now, ion-sensitive field-effect transistors (ISFETs) have been applied for chemosensing (Janata, 2004). These ISFETs have been devised using metal oxide field-effect transistors (MOSFETs). After the first successful application of ISFETs (Berg- veld, 1970), various reports have described similar devices for determination of different analytes of interest (Jimenez-Jorquera et al., 2010; Lee et al., 2009). As an improvement to isolate FET from the chemical environment, an extended-gate field-effect transistor (EG-FET) was devised (Batista et al., 2006; Chen et al., 2011; Chi et al., 2000; Yin et al., 2000). In this transistor, the re- cognition or chemically sensitive unit was deposited on surface of the gate extending from FET. The experimental setup prepared that way showed major advantage of flexibility in the gate shape (Chi et al., 2000). Advantageously, without a need of the use of expensive instruments and reagents, minute changes in potential at the gate surface due to the presence of charged biomolecules/ analytes, it was possible to convert into detectable electric signals. Additionally, the stability of FET characteristics to the ambient environment is greatly improved, and more importantly, packing and transportation of such a setup for field applications is rather easy. In various applications sensitivity provided by the EG-FET transduction was appreciable (Casalini et al., 2013; Chen et al., 2011; Selvanayagam et al., 2002). Typically, however, selectivity was poor. Therefore, there is still a need to improve selectivity in this device. For selective determination of the analyte of interest in the presence of interferences nowadays a synthetic receptor Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/bios Biosensors and Bioelectronics http://dx.doi.org/10.1016/j.bios.2015.06.073 0956-5663/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: knoworyta@ichf.edu.pl (K. Noworyta). Biosensors and Bioelectronics 74 (2015) 526–533