Biophysical Phenomenon-Based Separation of Platelet-Poor Plasma from Blood

An acoustofluidic device for the automated separation of platelet-reduced plasma from whole blood

Separating plasma from whole blood is an important sample processing technique required for fundamental biomedical research, medical diagnostics, and therapeutic applications. Traditional protocols for plasma isolation require multiple centrifugation steps or multiunit microfluidic processing to sequentially remove large red blood cells (RBCs) and white blood cells (WBCs), followed by the removal of small platelets. Here, we present an acoustofluidic platform capable of efficiently removing RBCs, WBCs, and platelets from whole blood in a single step. By leveraging differences in the acoustic impedances of fluids, our device generates significantly greater forces on suspended particles than conventional microfluidic approaches, enabling the removal of both large blood cells and smaller platelets in a single unit. As a result, undiluted human whole blood can be processed by our device to remove both blood cells and platelets (>90%) at low voltages (25 Vpp). The ability to successfully remove blood cells and platelets from plasma without altering the properties of the proteins and antibodies present creates numerous potential applications for our platform in biomedical research, as well as plasma-based diagnostics and therapeutics. Furthermore, the microfluidic nature of our device offers advantages such as portability, cost efficiency, and the ability to process small-volume samples.

Blood component separation in straight microfluidic channels

Separation of blood components is required in many diagnostic applications and blood processes. In laboratories, blood is usually fractionated by manual operation involving a bulk centrifugation equipment, which significantly increases logistic burden. Blood sample processing in the field and resource-limited settings cannot be readily implemented without the use of microfluidic technology. In this study, we developed a small footprint, rapid, and passive microfluidic channel device that relied on margination and inertial focusing effects for blood component separation. No blood dilution, lysis, or labeling step was needed as to preserve sample integrity. One main innovation of this work was the insertion of fluidic restrictors at outlet ports to divert the separation interface into designated outlet channels. Thus, separation efficiency was significantly improved in comparison to previous works. We demonstrated different operation modes ranging from platelet or plasma extraction from human whole blood to platelet concentration from platelet-rich plasma through the manipulation of outlet port fluidic resistance. Using straight microfluidic channels with a high aspect ratio rectangular cross section, we demonstrated 95.4% platelet purity extracted from human whole blood. In plasma extraction, 99.9% RBC removal rate was achieved. We also demonstrated 2.6× concentration of platelet-rich plasma solution to produce platelet concentrate. The extraction efficiency and throughput rate are scalable with continuous and clog-free recirculation operation, in contrast to other blood fractionation approaches using filtration membranes or affinity-based purification methods. Our microfluidic blood separation method is highly tunable and versatile, and easy to be integrated into multi-step blood processing and advanced sample preparation workflows.

Experimental Characterization of a Microfluidic Device Based on Passive Crossflow Filters for Blood Fractionation

The separation of red blood cells (RBCs) from blood plasma and the analysis of individual RBCs are of great importance, as they provide valuable information regarding the health of their donor. Recent developments in microfluidics and microfabrication have contributed to the fabrication of microsystems with complex features to promote the separation and analysis of RBCs. In this work, the separation capacity of a multi-step crossflow microfluidic device was evaluated by using a blood analogue fluid made by Brij L4 micelles and human RBCs separated from whole blood, suspended in a solution with hematocrits (Ht) of 0.5 and 1%. All the samples collected at the outlets of the device were experimentally analyzed and compared. The absorbance spectrum was also measured for the prepared blood samples. The results indicate that the tested blood analogue fluid has exhibited a flow behavior similar to that of blood. In addition, the optical absorbance spectrophotometry revealed that it was possible to evaluate the separation efficiency of the microfluidic device, concluding that the concentration of cells was lower at the most lateral outside outlets of the microchannel due to the cumulative effect of the multiple cross-flow filters.