title: Surface properties and electromagnetic excitation of a piezoelectric gallium phosphate biosensor.
abstract: The surface properties of GaPO4 have been studied by secondary ion mass spectrometry, X-ray photoelectron spectroscopy and electromagnetic acoustic wave excitation in order to explore the potential of this relatively new piezoelectric material as a biosensor. The X-ray photoelectron spectrum of the substrate shows a Ga-rich surface (Ga:P = 1.4), while the negative secondary ion mass spectrum is similar to that of other phosphates, with PO3- and PO2- being the main fragments derived from the substrate. Surface analysis reveals that the linker protein for biotinylated moieties, neutravidin, is both readily chemisorbed to bare gallium phosphate at pH 7.5 and attached to p-hydroxy benzaldehyde-treated devices, establishing the possibility to exploit the surface chemistry of the phosphate for the fabrication of an electrode-free acoustic wave biosensor. Preliminary results regarding the detection of the adsorption of neutravidin with an electromagnetic field-excited GaPO4 device incorporated in a FIA configuration showed comparable results with those obtained with a quartz-sensor equivalent. The frequency shift for the adsorbed protein layer at the device fundamental frequency was 200 Hz and the noise was routinely around 13 Hz. The possibility to use the electrodeless acoustic GaPO4 device at higher harmonics in the liquid phase has also been confirmed.
authors.affiliation: Department of Chemistry, University of Toronto, 80 St. George St., Toronto, Ontario M5S 3H6, Canada.
authors.forename: Alina
authors.initials: A
authors.lastname: Vasilescu
authors.forename: Scott M
authors.initials: SM
authors.lastname: Ballantyne
authors.forename: Larisa-Emilia
authors.initials: LE
authors.lastname: Cheran
authors.forename: Michael
authors.initials: M
authors.lastname: Thompson
mesh_terms: D015374:Biosensing Techniques; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods; D055590:Electromagnetic Phenomena; D005708:Gallium; D013499:Surface Properties
chemical_list: D005708:Gallium