Biosensors and Bioelectronics 24 (2008) 742–747 Contents lists available at ScienceDirect Biosensors and Bioelectronics journal homepage: www.elsevier.com/locate/bios Synergie between molecular imprinted polymer based on solid-phase extraction and quartz crystal microbalance technique for 8-OHdG sensing Arzu Ersöz a,∗ , S. Emir Diltemiz a , A. Atılır Özcan a , Adil Denizli b , Rıdvan Say a,c a Department of Chemistry, Anadolu University, Eskis ¸ ehir, Turkey b Department of Chemistry, Hacettepe University, Ankara, Turkey c B ˙ IBAM (Plant, Drug and Scientific Researches Center), Anadolu University, Eskis ¸ ehir, Turkey article info Article history: Received 24 March 2008 Received in revised form 23 June 2008 Accepted 24 June 2008 Available online 12 July 2008 Keywords: Molecularly imprinted polymer (MIP) Quartz crystal microbalance (QCM) 8-Hydroxy-2 ′ -deoxyguanosine (8-OHdG) Metal–chelate interaction abstract Recently, the 8-hydroxy-2 ′ -deoxyguanosine (8-OHdG) has been used as a marker to determine the oxida- tive stress. There is no any cheap and easy determination method based on chips and sensor systems for the determination of 8-OHdG. In this study, we have proposed imprinting methods for 8-OHdG recognition and determination using methacryloylamidohistidine-platinum(II) [MAH-Pt(II)] as a new metal-chelating monomer. The study includes the solid-phase extraction (SPE) of blood sample by a new 8-OHdG imprinted sorbent and the measurement of binding interaction of 8-OHdG imprinted quartz crystal microbalance (QCM) sensor via ligand interaction. 8-OHdG imprinted sorbent has prepared by bulk polymerization of MAH-Pt(II) and N-N ′ -methylenebisacrylamide. 8-OHdG imprinted sensor has prepared on a QCM chip coating the thiol pretreated Au electrode. At the end of these steps, a thin molecular imprinted polymer (MIP) film for the detection of 8-OHdG has developed and analytical performance of QCM sensor which has prepared using MIP was investigated. The affinity constant (K a ) for 8-OHdG using MAH-Pt-based thin film has determined by using the Scatchard method. The average percentage recovery of 8-OHdG from plasma samples was found as 80% by using of 8-OHdG imprinted SPE material. At the last step, 8-OHdG level in several blood plasma has been determined by this improved QCM sensor. The obtained results confirmed that the 8-OHdG level in cancer patient’s blood was significantly higher than in general subjects. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Oxidative damage to DNA in cells by reactive oxygen species (ROS) is a well-documented process (Dizdaroglu, 1992). Living organisms are continuously exposed to ROS, generated as a result of normal biochemical reactions and from various external factors relating to lifestyle and the environment such as tobacco smok- ing (Loft et al., 1992) and air pollution (Loft et al., 1999). Oxidative damage to DNA has also been implicated in the pathophysiology of a wide variety of human diseases including cancer, atherosclerosis, neurodegenerative disorders, and the aging process (Halliwell and Gutteridge, 1999). Because the reactive oxidants are not suitable for analysis, oxi- dized bases like 8-hydroxy-2 ′ -deoxyguanosine (8-OHdG) are used as biomarkers for DNA oxidative damage (Halliwell, 1999; Loft et al., 1993). In 1991, Szatrowski and Nathan (Szatrowski and Nathan, ∗ Corresponding author at: Anadolu Universitesi, Fen Fakültesi, Kimya Bölümü, Yunus Emre Kampüsü, 26470 Eskis ¸ehir, Turkey. Tel.: +90 222 3350580/5821; fax: +90 222 3204910. E-mail address: arzuersoz@anadolu.edu.tr (A. Ersöz). 1991) first reported that some human cancer cell lines can produce large amounts of H 2 O 2 . Antioxidant enzymes such as superox- ide dismutase and catalase also appear to be downregulated in cancer cells (Sun, 1990; Sato et al., 1992; Jaruga et al., 1994). Other studies have concluded that several kinds of human can- cer tissues, such as lung carcinomas and renal cell carcinomas, show higher levels of DNA oxidation compared with correspond- ing normal tissue controls, as determined by measurements of 8-OHdG (Kondo et al., 1999). The amount of 8-OHdG has been also found to increase progressively with age in both nuclear and mitochondrial DNA although the rate of increase with age is much greater in mitochondrial DNA. Nevertheless, oxidized levels of nuclear DNA are even greater in Alzheimer’s disease (AD) than in age matched controls (Gabbita et al., 1998). Various analytical methods have been employed for the determination of 8-OHdG. Most of these methods are based on capillary electrophoresis (Arnett et al., 2005), HPLC (Samcová et al., 2004) and immunoaffin- ity chromatography–monoclonal antibody-based ELISA (Yin et al., 1995). These methods are expensive, and require pretreatment. The research for highly selective, low cost, stable, sensitive, and foolproof chemical sensors is an attractive field. Quartz crystal microbalance (QCM) is well applicable to sensitive and selective 0956-5663/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.bios.2008.06.058