title: Affinity two-phase partitioning in acoustically levitated drops.
abstract: Miniaturized (<1 microL) biospecific affinity two-phase partitioning in an acoustically levitated drop is described. Miniaturization commonly gives unfavorable surface/volume ratios, but in the levitation approach adsorption problems are minimized since the only surrounding wall is the liquid/air interface of the drop. Biotinylated liposomes were partitioned in aqueous poly(ethylene glycol)/dextran two-phase drops with NeutrAvidin-dextran as the affinity ligand. A two-phase drop was trapped and manipulated in a node of a standing ultrasonic wave. Alternatively, a two-phase system was formed by levitation and evaporation of a polymer one-phase drop. Phase mixing was achieved by adjusting the ultrasonic field and phase separation by readjusting the field. NeutrAvidin-dextran brought about the redistribution of biotinylated liposomes from the poly(ethylene glycol)-rich phase into the dextran-rich phase. Thus, an entire affinity two-phase separation procedure, including mixing of the phases and incubation to allow affinity interactions to develop under constant volume, followed by phase separation under controlled evaporation, can be performed in a single levitated drop. This miniaturized technique would allow the separation of biologically active membranes or organelles from individual cells for analysis.
authors.affiliation: Technical Analytical Chemistry and Biochemistry, Center for Chemistry and Chemical Engineering, Lund University, PO Box 124, SE-221 00 Lund, Sweden.
authors.forename: Sabina
authors.initials: S
authors.lastname: Santesson
authors.forename: Irene
authors.initials: I
authors.lastname: Barinaga-Rementeria Ramírez
authors.forename: Peter
authors.initials: P
authors.lastname: Viberg
authors.forename: Bengt
authors.initials: B
authors.lastname: Jergil
authors.forename: Staffan
authors.initials: S
authors.lastname: Nilsson