Acoustic whole blood plasmapheresis chip for prostate specific antigen microarray diagnostics.

The generation of high quality plasma from whole blood is of major interest for many biomedical analyses and clinical diagnostic methods. However, it has proven to be a major challenge to make use of microfluidic separation devices to process fluids with high cell content, such as whole blood. Here, we report on an acoustophoresis based separation chip that prepares diagnostic plasma from whole blood linked to a clinical application. This acoustic separator has the capacity to sequentially remove enriched blood cells in multiple steps to yield high quality plasma of low cellular content. The generated plasma fulfills the standard requirements (<6.0 x 10(9) erythrocytes/L) recommended by the Council of Europe. Further, we successfully linked the plasmapheresis microchip to our previously developed porous silicon sandwich antibody microarray chip for prostate specific antigen (PSA) detection. PSA was detected by good linearity (R(2) > 0.99) in the generated plasma via fluorescence readout without any signal amplification at clinically relevant levels (0.19-21.8 ng/mL).

Free flow acoustophoresis: microfluidic-based mode of particle and cell separation.

A novel method, free flow acoustophoresis (FFA), capable of continuous separation of mixed particle suspensions into multiple outlet fractions is presented. Acoustic forces are utilized to separate particles based on their size and density. The method is shown to be suitable for both biological and nonbiological suspended particles. The microfluidic separation chips were fabricated using conventional microfabrication methods. Particle separation was accomplished by combining laminar flow with the axial acoustic primary radiation force in an ultrasonic standing wave field. Dissimilar suspended particles flowing through the 350-microm-wide channel were thereby laterally translated to different regions of the laminar flow profile, which was split into multiple outlets for continuous fraction collection. Using four outlets, a mixture of 2-, 5-, 8-, and 10-microm polystyrene particles was separated with between 62 and 94% of each particle size ending up in separate fractions. Using three outlets and three particle sizes (3, 7, and 10 microm) the corresponding results ranged between 76 and 96%. It was also proven possible to separate normally acoustically inseparable particle types by manipulating the density of the suspending medium with cesium chloride. The medium manipulation, in combination with FFA, was further used to enable the fractionation of red cells, platelets, and leukocytes. The results show that free flow acoustophoresis can be used to perform complex separation tasks, thereby offering an alternative to expensive and time-consuming methods currently in use.