Example 3
Magnetizable beads are 1.3 um diameter BioMag magnetic particles from Bangs Laboratories. Beads are coated (by the manufacturer) with anti-Rabbit IgG. Beads are dispersed at 14 mg/mL in tris-buffered sucrose (or, alternatively, tris buffered saline) containing 3% bovine serum albumin and rabbit anti-human red blood cell IgG, from CedarLane at >=1.15 mg/mL. Aliquots (10 uL of this dispersion were dispensed into conical tubes and lyophilized (frozen in liquid N2 and lyophilized for approximately 24 hrs. at −70 C) prior to insertion into a slot in the cartridge housing. The rabbit antibody binds both to the red cells and to the anti-rabbit IgG-coated beads and forms a co-agglutinate of beads and red cells.
The lyophilized magnetizable bead pellet was re-suspended by adding 20 uL of whole blood then aspirating and dispensing at least 8 times (approximately 1.5 min) into a conical tube.
Blood was separated by placing the tip (in a vertical orientation) in a strong, horizontally oriented magnetic field. Typically 8 uL of essentially red cell free plasma with no observable hemolysis was recovered from a 20 ul blood sample (70% yield). Recovery of analytes (compared to plasma not exposed to the magnetic separation) was close to 100% for Protein-C, VEGF, PlGF, Insulin, GIP and GIP-1.