The Concentration and Separation Of Blood Components Using Acoustic Radiation Force

The concentration of whole blood has a wide spectrum of medical uses, especially in blood transfusions for patients suffering acute blood loss from trauma or surgery. However, current methods rely on centrifugation, which has a tendency to cause fragmentation and deformation of cells. Acoustic standing waves are considered to be a gentler means to concentrate blood cells, but generally suffer from flow rate limitations of >10³fold, functioning only on the microscale. To address this issue, we have developed a novel ultrasound technology that works at the macroscale, enabling it to process flow rates that would typically be required to handle medically relevant volumes.

In this study, we have applied the principles of acoustic radiation at the macroscale to re-concentrate 10X diluted porcine blood by trapping the blood cells within a standing wave, resulting in the clumping of cells and platelets, ultimately leading to enhanced gravitational settling. Complete blood counts were measured with a VetScan HM5 hematology analyzer. Using an acoustic force generated by power levels up to 25 Watts, no lysing was observed in any of the experiments. The inlet flow rate through the device was 16 ml/min, and the concentrate flow rate of the blood components was typically 1 ml/min. The transducer was a 2 MHz PZT-8 operating at 10 W, and it was oriented to create an acoustic standing wave perpendicular to the flow direction. Results indicate successful capture of red blood cells, white blood cells, and platelets with separation efficiencies in excess of 90% in a single pass. Furthermore, the blood components were all reconcentrated back to levels similar to those in whole blood.

Subsequent experiments and conditions have allowed for the separation of blood components, suggesting that the future development of acoustic methods to perform blood re-concentration procedures such as erythropheresis, leukapheresis and plateletpheresis in a gentler manner than current methods holds great promise. With almost 15 million transfusions performed each year in the United States, this technology has the potential to make a significant impact on the medical community, particularly for treatment of critically ill patients. Additionally, the novel technology has also demonstrated performance in separating lipid particles from blood, thus indicating its utility for reducing the occurrence of lipid microemboli during re-transfusion of shed blood in cardiopulmonary bypass surgeries, which have been linked with post-operative neurocognitive complications. As a result, the novel acoustophoretic technology may become a general purpose platform for achieving separation in a variety of biomedical applications.