Concentration and purification of human immunodeficiency virus type 1 virions by microfluidic separation of superparamagnetic nanoparticles.

The low concentration and complex sample matrix of many clinical and environmental viral samples presents a significant challenge in the development of low cost, point-of-care viral assays. To address this problem, we investigated the use of a microfluidic passive magnetic separator combined with on-chip mixer to both purify and concentrate whole-particle human immunodeficiency virus type 1 (HIV-1) virions. Virus-containing plasma samples are first mixed to allow specific binding of the viral particles with antibody-conjugated superparamagnetic nanoparticles, and several passive mixer geometries were assessed for their mixing efficiencies. The virus-nanoparticle complexes are then separated from the plasma in a novel magnetic separation chamber, where packed micrometer-sized ferromagnetic particles serve as high magnetic gradient concentrators for an externally applied magnetic field. Thereafter, a viral lysis buffer was flowed through the chip and the released HIV proteins were assayed off-chip. Viral protein extraction efficiencies of 62% and 45% were achieved at 10 and 30 muL/min throughputs, respectively. More importantly, an 80-fold concentration was observed for an initial sample volume of 1 mL and a 44-fold concentration for an initial sample volume of 0.5 mL. The system is broadly applicable to microscale sample preparation of any viral sample and can be used for nucleic acid extraction as well as 40-80-fold enrichment of target viruses.