title: Surface protein gradients generated in sealed microchannels using spatially varying helium microplasma.
abstract: Spatially varied surface treatment of a fluorescently labeled Bovine Serum Albumin (BSA) protein, on the walls of a closed (sealed) microchannel is achieved via a well-defined gradient in plasma intensity. The microchips comprised a microchannel positioned in-between two microelectrodes (embedded in the chip) with a variable electrode separation along the length of the channel. The channel and electrodes were 50 μm and 100 μm wide, respectively, 50 μm deep, and adjacent to the channel for a length of 18 mm. The electrode separation distance was varied linearly from 50 μm at one end of the channel to a maximum distance of 150, 300, 500, or 1000 μm to generate a gradient in helium plasma intensity. Plasma ignition was achieved at a helium flow rate of 2.5 ml/min, 8.5 kVpk-pk, and 10 kHz. It is shown that the plasma intensity decreases with increasing electrode separation and is directly related to the residual amount of BSA left after the treatment. The plasma intensity and surface protein gradient, for the different electrode gradients studied, collapse onto master curves when plotted against electrode separation. This precise spatial control is expected to enable the surface protein gradient to be tuned for a range of applications, including high-throughput screening and cell-biomolecule-biomaterial interactions.
authors.affiliation: Mawson Institute, University of South Australia , Mawson Lakes, South Australia 5095, Australia.
authors.forename: Pascal
authors.initials: P
authors.lastname: Wettstein
authors.affiliation: Ian Wark Research Institute, University of South Australia , Mawson Lakes, South Australia 5095, Australia.
authors.forename: Craig
authors.initials: C
authors.lastname: Priest
authors.affiliation: Mawson Institute, University of South Australia , Mawson Lakes, South Australia 5095, Australia.
authors.forename: Sameer A
authors.initials: SA
authors.lastname: Al-Bataineh
authors.affiliation: Mawson Institute, University of South Australia , Mawson Lakes, South Australia 5095, Australia.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Short
authors.affiliation: Department of Electrical Engineering and Electronics, The University of Liverpool , Brownlow Hill, Liverpool L69 3GJ, United Kingdom.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Bryant
authors.affiliation: Department of Electrical Engineering and Electronics, The University of Liverpool , Brownlow Hill, Liverpool L69 3GJ, United Kingdom.
authors.forename: James W
authors.initials: JW
authors.lastname: Bradley
authors.affiliation: Mawson Institute, University of South Australia , Mawson Lakes, South Australia 5095, Australia.
authors.forename: Suet P
authors.initials: SP
authors.lastname: Low
authors.affiliation: Ian Wark Research Institute, University of South Australia , Mawson Lakes, South Australia 5095, Australia.
authors.forename: Luke
authors.initials: L
authors.lastname: Parkinson
authors.affiliation: Mawson Institute, University of South Australia , Mawson Lakes, South Australia 5095, Australia.
authors.forename: Endre J
authors.initials: EJ
authors.lastname: Szili