Bioaffinity Sensor Based on Nanoarchitectonic Films: Control of the Specific Adsorption of Proteins through the Dual Role of an Ethylene Oxide Spacer Johanna Davila, † Delphine Toulemon, † Tony Garnier, †,‡ Aure ́ lie Garnier, † Bernard Senger, §,∥ Jean-Claude Voegel, §,∥ Philippe J. Me ́ sini, †,‡ Pierre Schaaf, †,‡,§,∥,⊥,# Fouzia Boulmedais,* ,†,‡ and Loïc Jierry †,‡,⊥ † Centre National de la Recherche Scientifique, Unite ́ Propre de Recherche 22, Institut Charles Sadron, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France ‡ International Center for Frontier Research in Chemistry, 8 allé e Gaspard Monge, 67000 Strasbourg, France § Institut National de la Sante ́ et de la Recherche Me ́ dicale, Unite ́ 1121, 11 rue Humann, 67085 Strasbourg Cedex, France ∥ Faculte ́ de Chirurgie Dentaire, Universite ́ de Strasbourg, 1 Place de l’Hô pital, 67000 Strasbourg, France ⊥ Ecole de Chimie, Polyme ̀ res et Maté riaux, 25 rue Becquerel, 67087 Strasbourg Cedex 2, France # Institut Universitaire de France, 103 Boulevard Saint-Michel, 75005 Paris, France * S Supporting Information ABSTRACT: The identification and quantification of biomarkers or proteins is a real challenge in allowing the early detection of diseases. The functionalization of the biosensor surface has to be properly designed to prevent nonspecific interactions and to detect the biomolecule of interest specifically. A multilayered nanoarchitecture, based on polyelectrolyte multilayers (PEM) and the sequential immobilization of streptavidin and a biotinylated antibody, was elaborated as a promising platform for the label-free sensing of targeted proteins. We choose ovalbumin as an example. Thanks to the versatility of PEM films, the platform was built on two types of sensor surface and was evaluated using both optical- and viscoelastic- based techniques, namely, optical waveguide lightmode spectroscopy and the quartz crystal microbalance, respectively. A library of biotinylated poly(acrylic acids) (PAAs) was synthesized by grafting biotin moieties at different grafting ratios (GR). The biotin moieties were linked to the PAA chains through ethylene oxide (EO) spacers of different lengths. The adsorption of the PAA- EO n -biotin (GR) layer on a PEM precursor film allows tuning the surface density in biotin and thus the streptavidin adsorption mainly through the grafting ratio. The nonspecific adsorption of serum was reduced and even suppressed depending on the length of the EO arms. We showed that to obtain an antifouling polyelectrolyte the grafting of EO 9 or EO 19 chains at 25% in GR is sufficient. Thus, the spacer has a dual role: ensuring the antifouling property and allowing the accessibility of biotin moieties. Finally, an optimized platform based on the PAA-EO 9 -biotin (25%)/streptavidin/biotinylated-antibody architecture was built and demonstrated promising performance as interface architecture for bioaffinity sensing of a targeted protein, in our case, ovalbumin. ■ INTRODUCTION The identification and quantification of biomarkers and proteins are important issues that allow the early detection of diseases. 1,2 Present at low concentrations in complex body fluids (e.g., serum, plasma, and urine), 3 biomarkers have to be detected specifically and in a reproducible manner through biosensors. Nonspecific protein binding from plasma or serum constitutes one of the limitations of biosensors. 4 Antifouling surfaces able to bind target molecules specifically are required for the development of biosensing platforms based on surface- sensitive analytical techniques. Label-free technology for biodetection is a current field of research that is commonly based on changes in optical or viscoelastic properties at the sensor/biological fluid interface caused by the binding of biomolecules. 5 Optical sensing has been extensively used for drug screening for many years on the basis of surface plasmon resonance (SPR) 6,7 or optical waveguide light-mode spectros- copy (OWLS). 8 The quartz crystal microbalance (QCM), based on viscoelastic changes, is less used as a biosensor even if Special Issue: Interfacial Nanoarchitectonics Received: November 15, 2012 Revised: January 24, 2013 Published: January 24, 2013 Article pubs.acs.org/Langmuir © 2013 American Chemical Society 7488 dx.doi.org/10.1021/la3045779 | Langmuir 2013, 29, 7488−7498