title: Nanostructured porous Si optical biosensors: effect of thermal oxidation on their performance and properties.
abstract: The influence of thermal oxidation conditions on the performance of porous Si optical biosensors used for label-free and real-time monitoring of enzymatic activity is studied. We compare three oxidation temperatures (400, 600, and 800 °C) and their effect on the enzyme immobilization efficiency and the intrinsic stability of the resulting oxidized porous Si (PSiO2), Fabry-Pérot thin films. Importantly, we show that the thermal oxidation profoundly affects the biosensing performance in terms of greater optical sensitivity, by monitoring the catalytic activity of horseradish peroxidase and trypsin-immobilized PSiO2. Despite the significant decrease in porous volume and specific surface area (confirmed by nitrogen gas adsorption-desorption studies) with elevating the oxidation temperature, higher content and surface coverage of the immobilized enzymes is attained. This in turn leads to greater optical stability and sensitivity of PSiO2 nanostructures. Specifically, films produced at 800 °C exhibit stable optical readout in aqueous buffers combined with superior biosensing performance. Thus, by proper control of the oxide layer formation, we can eliminate the aging effect, thus achieving efficient immobilization of different biomolecules, optical signal stability, and sensitivity.
authors.affiliation: The Inter-Departmental Program of Biotechnology, ‡Department of Biotechnology and Food Engineering, and ∥The Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology , Haifa 32000, Israel.
authors.forename: Giorgi
authors.initials: G
authors.lastname: Shtenberg
authors.forename: Naama
authors.initials: N
authors.lastname: Massad-Ivanir
authors.forename: Ljiljana
authors.initials: L
authors.lastname: Fruk
authors.forename: Ester
authors.initials: E
authors.lastname: Segal
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D004800:Enzymes, Immobilized / Q000737:chemistry* / Q000378:metabolism; D006735:Horseradish Peroxidase / Q000737:chemistry / Q000378:metabolism; D006358:Hot Temperature; D049329:Nanostructures / Q000737:chemistry*; D010084:Oxidation-Reduction; D016062:Porosity; D012825:Silicon / Q000737:chemistry*
chemical_list: D004800:Enzymes, Immobilized; D006735:Horseradish Peroxidase; D012825:Silicon
keywords: biosensor; enzyme; label free; nanostructure; porous Si; thermal oxidation