Density-based diamagnetic separation: devices for detecting binding events and for collecting unlabeled diamagnetic particles in paramagnetic solutions.
This paper describes the fabrication of a fluidic device for detecting and separating diamagnetic materials that differ in density. The basis for the separation is the balance of the magnetic and gravitational forces on diamagnetic materials suspended in a paramagnetic medium. The paper demonstrates two applications of separations involving particles suspended in static fluids for detecting the following: (i) the binding of streptavidin to solid-supported biotin and (ii) the binding of citrate-capped gold nanoparticles to amine-modified polystyrene spheres. The paper also demonstrates a microfluidic device in which polystyrene particles that differ in their content of CH2Cl groups are continuously separated and collected in a flowing stream of an aqueous solution of GdCl3. The procedures for separation and detection described in this paper require only gadolinium salts, two NdFeB magnets, and simple microfluidic devices fabricated from poly(dimethylsiloxane). This device requires no power, has no moving parts, and may be suitable for use in resource-poor environments.
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.
Adam
A
Winkleman
Raquel
R
Perez-Castillejos
Katherine L
KL
Gudiksen
Scott T
ST
Phillips
Mara
M
Prentiss
George M
GM
Whitesides
D000268:Adhesiveness; D002138:Calibration; D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry; D044085:Microfluidics / Q000295:instrumentation* / Q000379:methods*; D008863:Microspheres; D011137:Polystyrenes / Q000737:chemistry / Q000302:isolation & purification; D012996:Solutions; D055672:Static Electricity
D011137:Polystyrenes; D012996:Solutions