title: Multi-modal particle manipulator to enhance bead-based bioassays.
abstract: By sequentially pushing micro-beads towards and away from a sensing surface, we show that ultrasonic radiation forces can be used to enhance the interaction between a functionalised glass surface and polystyrene micro-beads, and identify those that bind to the surface by illuminating bound beads using an evanescent field generated by guided light. The movement towards and immobilisation of streptavidin coated beads onto a biotin functionalised waveguide surface is achieved by using a quarter-wavelength mode pushing beads onto the surface, while the removal of non-specifically bound beads uses a second quarter-wavelength mode which exhibits a kinetic energy maximum at the boundary between the carrier layer and fluid, drawing beads towards this surface. This has been achieved using a multi-modal acoustic device which exhibits both of these quarter-wavelength resonances. Both 1-D acoustic modelling and finite element analysis has been used to design this device and to investigate the spatial uniformity of the field. We demonstrate experimentally that 90% of specifically bound beads remain attached after applying ultrasound, with 80% of non-specifically bound control beads being successfully removed acoustically. This approach overcomes problems associated with lengthy sedimentation processes used for bead-based bioassays and surface (electrostatic) forces, which delay or prevent immobilisation. We explain the potential of this technique in the development of DNA and protein assays in terms of detection speed and multiplexing.
authors.affiliation: School of Engineering Sciences, University of Southampton, Southampton SO17 1BJ, UK.
authors.forename: P
authors.initials: P
authors.lastname: Glynne-Jones
authors.forename: R J
authors.initials: RJ
authors.lastname: Boltryk
authors.forename: M
authors.initials: M
authors.lastname: Hill
authors.forename: F
authors.initials: F
authors.lastname: Zhang
authors.forename: L
authors.initials: L
authors.lastname: Dong
authors.forename: J S
authors.initials: JS
authors.lastname: Wilkinson
authors.forename: T
authors.initials: T
authors.lastname: Brown
authors.forename: T
authors.initials: T
authors.lastname: Melvin
authors.forename: N R
authors.initials: NR
authors.lastname: Harris
mesh_terms: D000162:Acoustics / Q000295:instrumentation*; D015374:Biosensing Techniques / Q000295:instrumentation*; D001710:Biotin; D004247:DNA / Q000032:analysis / Q000737:chemistry; D004867:Equipment Design; D020342:Finite Element Analysis; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D008863:Microspheres; D008962:Models, Theoretical; D055620:Optical Phenomena; D011137:Polystyrenes; D019809:Streptavidin
chemical_list: D011137:Polystyrenes; D001710:Biotin; D004247:DNA; D019809:Streptavidin