title: Surface functionalization of germanium ATR devices for use in FTIR-biosensors.
abstract: Biosensors based on intrinsic detection methods have attracted growing interest. The use of Fourier transform infra-red (FTIR) spectroscopy with the attenuated internal total reflection (ATR) mode, in the biodetection context, requires appropriate surface functionalization of the ATR optical element. Here, we report the direct grafting of a thin organic layer (about 20 A depth) on the surface of a germanium crystal. This covering, constructed with novel amphiphilic molecules 2b (namely, 2,5,8,11,14,17,20-heptaoxadocosan-22-yl-3-(triethoxysilyl) propylcarbamate), is stable for several hours under phosphate buffered saline (PBS) flux and features protein-repulsive properties. Photografting of molecule 5 (namely, O-succinimidyl 4-(p-azidophenyl)butanoate) affords the activated ATR element, ready for the covalent fixation of receptors, penicillin recognizing proteins BlaR-CTD for instance. The different steps of the previous construction have been monitored by water contact angle (theta(w)) measurements, spectroscopic ellipsometry (covering depth), X-ray photoelectron spectroscopy (XPS) by using a fluorinated tag for the control of surface reactivity, and FTIR-ATR spectroscopy for the structural analysis of grafted molecules. Indeed, contrarily to silicon device, germanium device offers a broad spectral window (1000-4000 cm(-1)) and thus amide I and II absorption bands can be recorded. This work lays the foundations for the construction of novel FTIR biosensors.
authors.affiliation: Unité de Chimie Organique et Médicinale, Université Catholique de Louvain, Bâtiment Lavoisier, Place Louis Pasteur 1, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Devouge
authors.forename: Joséphine
authors.initials: J
authors.lastname: Conti
authors.forename: Andréa
authors.initials: A
authors.lastname: Goldsztein
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Gosselin
authors.forename: Alain
authors.initials: A
authors.lastname: Brans
authors.forename: Michel
authors.initials: M
authors.lastname: Voué
authors.forename: Joël
authors.initials: J
authors.lastname: De Coninck
authors.forename: Fabrice
authors.initials: F
authors.lastname: Homblé
authors.forename: Erik
authors.initials: E
authors.lastname: Goormaghtigh
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Marchand-Brynaert
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D005857:Germanium; D011506:Proteins; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D011506:Proteins; D005857:Germanium