title: XPS and AFM characterization of the enzyme glucose oxidase immobilized on SiO(2) surfaces.
abstract: A process to immobilize the enzyme glucose oxidase on SiO2 surfaces for the realization of integrated microbiosensors was developed. The sample characterization was performed by monitoring, step by step, oxide activation, silanization, linker molecule (glutaraldehyde) deposition, and enzyme immobilization by means of XPS, AFM, and contact angle measurements. The control of the environment during the procedure, to prevent silane polymerization, and the use of oxide activation to obtain a uniform enzyme layer are issues of crucial importance. The correct protocol application gives a uniform layer of the linker molecule and the maximum sample surface coverage. This result is fundamental for maximizing the enzyme bonding sites on the sample surface and achieving the maximum surface coverage. Thin SiO2 layers thermally grown on a Si substrate were used. The XPS Si 2p signal of the substrate was monitored during immobilization. Such a signal is not completely shielded by the thin oxide layer and it is fully suppressed after the completion of the whole protocol. A power spectral density analysis on the AFM measurements showed the crucial role of both the oxide activation and the intermediate steps (silanization and linker molecule deposition) to obtain uniform immobilized enzyme coverage. Finally, enzymatic activity measurements confirmed the suitability of the optimized protocol.
authors.affiliation: CNR-IMM unità Catania, Stradale Primosole 50, 95121 Catania, Italy. sebania.libertino@imm.cnr.it
authors.forename: Sebania
authors.initials: S
authors.lastname: Libertino
authors.forename: Filippo
authors.initials: F
authors.lastname: Giannazzo
authors.forename: Venera
authors.initials: V
authors.lastname: Aiello
authors.forename: Antonino
authors.initials: A
authors.lastname: Scandurra
authors.forename: Fulvia
authors.initials: F
authors.lastname: Sinatra
authors.forename: Marcella
authors.initials: M
authors.lastname: Renis
authors.forename: Manuela
authors.initials: M
authors.lastname: Fichera
mesh_terms: D004583:Electrons; D004800:Enzymes, Immobilized; D005949:Glucose Oxidase / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D012822:Silicon Dioxide / Q000737:chemistry*; D013057:Spectrum Analysis; D013499:Surface Properties; D014965:X-Rays
chemical_list: D004800:Enzymes, Immobilized; D012822:Silicon Dioxide; D005949:Glucose Oxidase