A filtration cell (10) for a biological sample including an upper chamber for receiving the biological sample to be filtered, a lower chamber in fluid communication with the upper chamber, and a filtration membrane (14) positioned between the upper chamber and the lower chamber is disclosed. A surface of the filtration membrane has a contact angle >90°. The flow of the biological sample through the upper chamber may be tangential to the filtration membrane and a filtrate passing through the filtration membrane may be collected in the lower chamber. Also, a method of filtering a biological sample including passing the biological sample through an upper chamber of a filtration cell as described above and collecting a filtrate in the lower chamber is disclosed.