Biosensors and Bioelectronics 26 (2010) 1062–1067 Contents lists available at ScienceDirect Biosensors and Bioelectronics journal homepage: www.elsevier.com/locate/bios Disposable immunosensor for human cardiac troponin T based on streptavidin-microsphere modified screen-printed electrode Bárbara V.M. Silva a , Igor T. Cavalcanti a , Alessandra B. Mattos a , Patrícia Moura a , Maria Del Pilar T. Sotomayor b , Rosa F. Dutra a,∗ a Laboratório de Pesquisa em Diagnóstico/LAPED, Pronto Socorro Cardiológico de Pernambuco/PROCAPE, Universidade de Pernambuco, Rua dos Palmares, s/n, 50100-130 Recife-PE, Brazil b Instituto de Química de Araraquara, Universidade Estadual de São Paulo, UNESP, Campus Araraquara, São Paulo, Brazil article info Article history: Received 14 April 2010 Received in revised form 14 August 2010 Accepted 17 August 2010 Available online 21 August 2010 Keywords: Immunosensor Screen-printed electrode Myocardial infarction Troponin T abstract Screen-printed electrodes (SPE) have been widely used in the design of disposable sensors bringing advances in the use of electrochemical immunosensors for in field-clinical analysis. In this work, strep- tavidin polystyrene microspheres were incorporated to the electrode surface of SPEs in order to increase the analytical response of the cardiac troponin T (cTnT), a specific biomarker for the acute myocardial infarction diagnosis. The precise calculation of the stoichiometric streptavidin–biotin ratio [1:4] allowed the increase of sensitivity and stability of the immunosensor response to the cTnT analyte. The surface of the immunosensor was characterized by scanning electron microscopy and cyclic voltammetry. It was observed that the use of streptavidin microspheres significantly increased the analytical sensitivity of the electrode in 8.5 times, showing a curve with a linear response range between 0.1 and 10 ng mL -1 of cTnT and a detection limit of 0.2 ng mL -1 . The proposed SPE showed ease preparation and high sensitiv- ity allowing the detection of cTnT in the range of clinical levels. The new device coupled with a portable electrochemical analyzer shows great promise for point-of-care quantitative testing of necrosis cardiac proteins. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Immunoassays are considered the most currently commer- cial methods employed in hospitals and laboratories in clinical routine for diagnosis of several diseases exploring the specificity antigen–antibody interaction (Li et al., 2008). Despite exhibit- ing high sensitivity and selectivity, traditional immunoassays still have some drawbacks, such as time consuming, the dependence of equipment considered sophisticated and expensive, and the demand for skilled professionals (Huang et al., 2010). To minimiz- ing limitations imposed by traditional methods, immunosensors which combine the high specificity of traditional immunochemical methods, present several advantages as the possibility of point-of- care testing development (Viswanathan et al., 2009). SPE have been widely used in the design of disposable sen- sors. The screen printing microfabrication technology is nowadays well established for the production of thick-film electrochem- ical transducers. This technology allows the mass production of reproducible yet inexpensive and mechanically robust strip ∗ Corresponding author. Tel.: +55 81 3181 7179; fax: +55 81 3183 3302. E-mail addresses: rosa.dutra@pq.cnpq.br, rfiremandutra@yahoo.com.br (R.F. Dutra). solid electrodes. Other important features that these electrodes exhibit are related to the miniaturization of the correspond- ing device along with their ease of handling and manipulation in a disposable manner (Díaz-González et al., 2005). SPE could be constructed using a film technology by mixing graphite powder with epoxy resin resulting a composite that act not only as a transducer for the electrochemical signal generation, but also permit tightly incorporation of different substances as mediators, enzymes, antibody, and antigens (Cai et al., 2009). The application of nanomaterials integrated to the electrode surface has enabled the development of more sensitive and reproducible biosensors (Kerman et al., 2008). The integration of materials promotes increase of the electroactive area and the amount of immobilized molecules; in some cases, improving the electrical transfer (Jubete et al., 2009). The main classes of nano- materials applied to modify metal, glass or carbon surface in connection with electrochemical sensors are carbon nanotubes and nanoparticles (Martínez-Paredes et al., 2009). The nanoparticles of different sizes and nature can be easily functionalized offering reactive groups on the electrode surface, allowing a more stable and irreversible immobilization of enzymes, antigens, nucleic acid and antibodies, greatly increasing the biosensor response (Lin et al., 2008). 0956-5663/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.bios.2010.08.051