A polymer nanostructured Fabry–Perot interferometer based biosensor

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Biosensors and Bioelectronics 30 (2011) 128–132

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Biosensors and Bioelectronics journal homepage: www.elsevier.com/locate/bios

A polymer nanostructured Fabry–Perot interferometer based biosensor Tianhua Zhang a , Pushparaj Pathak a , Sukrut Karandikar a,b , Rebecca Giorno b , Long Que a,∗ a b

Institute for Micromanufacturing, Louisiana Tech University, Ruston, LA, USA School of Biological Sciences, Louisiana Tech University, Ruston, LA, USA

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Article history: Received 27 July 2011 Received in revised form 28 August 2011 Accepted 29 August 2011 Available online 6 September 2011 Keywords: Biosensing Fabry–Perot interferometer Nanostructures Localized surface plasmon resonance effect

a b s t r a c t A polymer nanostructured Fabry–Perot interferometer (FPI) based biosensor is reported. Different from a conventional FPI, the nanostructured FPI has a layer of Au-coated nanopores inside its cavity. The Au-coated nanostructure layer offers significant enhancement of optical transducing signals due to the localized surface plasmon resonance effect and also due to the significantly increased sensing surface area, which is up to at least two orders of magnitude larger than that of a conventional FPI-based biosensor. Using this technical platform, the immobilization of captures proteins (protein A) on the nanostructure layer and their binding with immunoglobulin G (IgG) has been monitored in real time, resulting in the shift of the interference fringes of the optical transducing signals. Current results show that the limit-ofdetection of the biosensor should be lower than 10 pg/mL for IgG-protein A binding. © 2011 Elsevier B.V. All rights reserved.

1. Introduction Label-free biosensing, a very efficient technique for biomedical, environmental monitoring and biology research applications, has become increasingly important. For the micro or nanoscale label-free biosensors, there are three main categories in terms of transducing mechanisms, which include electrical, mechanical and optical responses (Zheng et al., 2005; Wu et al., 2000; Zhao et al., 2006). Electrical transduction is enabled by semiconducting carbon nanotubes (CNTs) or semiconducting nanowires (NWs) where the electrical conductance of the CNTs or NWs changes upon the binding between the receptors immobilized on them and the targets (Zheng et al., 2005; Star et al., 2006). Mechanical transduction is achieved by microscale cantilevers. The binding between the targets and the receptors immobilized on the cantilever surface changes the cantilever’s surface stress. As a result, the cantilever bends and its resonant frequency shifts. Both of these responses of the cantilever have been utilized for label-free biosensing (Wu et al., 2000; Gupta et al., 2006). The major optical label-free techniques are propagating surface plasmon resonance (P-SPR) (Karlsson, 2004), Raman spectroscopy (Vo-Dinh et al., 2005) and surface enhanced Raman spectroscopy (SERS) (Fleischmann et al., 1974), localized SPR (L-SPR) (Zhao et al., 2006), liquid core optical ring resonator (LCORR) technology (White et al., 2006) and photonic crystal (PC) nanostructures (Mandal and Erickson, 2008; Chan et al., 2008). Surface plasmon (SP) can be

∗ Corresponding author at: 911 Hergot Avenue, Ruston, LA 71270, USA. Tel.: +1 318 257 5121; fax: +1 318 257 5104. E-mail address: [email protected] (L. Que). 0956-5663/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.bios.2011.08.042

excited at a metal and dielectric interface by a monochromatic or near-monochromatic optical source. The fields associated with the SPR extend into the medium adjacent to the interface and decay exponentially away from it. Penetration into the medium is in the range of
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