Abstract: Provided herein are devices and methods for extracting blood plasma from ultra-low volumes of blood. In some cases, the devices and methods use positive pressure to force a blood sample through a filter or a membrane. In some cases, the devices and methods use centrifugation to force a blood sample through a filter or a membrane. The devices and methods disclosed herein are suitable for the preparation of high-quality samples containing cell-free nucleic acids.

Abstract: A cassette assembly (1) comprises a cover (100), two cassette halves (200A, 200B) and a slider (300) comprising multiple test chambers (302). The cassette halves (200A, 200B) comprise waste tanks (230) in fluid connection with reservoirs (240), prefilled in one of the cassette halves (200A, 200B) with test agents. The particular design of the cassette halves (200A, 200B) enable forming predefined 5 volumes of liquid to achieve predefined concentrations of the test agents in the reservoirs (240) in one of the cassette halves (200A, 200B) and liquid in the reservoirs (240) in the other of the cassette halves (200A, 200B). Gradients of the test agents can then be established over the multiple test chambers (302).