Surface Acoustic Wave-Based Assessment of Red Blood Cell Viability Following Cryopreservation

Red blood cell (RBC) transfusion is critical for healthcare, with global annual demands exceeding 100 million units, making cryopreservation essential for stable supplies. However, cryopreservation can damage RBCs, making post-thaw viability assessment necessary. Current methods face limitations in achieving noninvasive, high-throughput, real-time, label-free, and interference-resistant analysis. Herein, we present a novel strategy for evaluating RBC viability by using a surface acoustic wave (SAW) sensor. Following centrifugation, stratified RBC suspensions from a Luer Lock syringe were injected into a microfluidic detection channel. Differential signal responses between the detection and reference channels of the SAW sensor were continuously monitored by using a custom-built amplitude-phase detection module. Experimental results demonstrated that the amplitude differential response of the SAW sensor can reliably distinguish between packed RBCs at 80% hematocrit and hemoglobin-containing 0.9% NaCl solution while remaining insensitive to the erythrocytic ghosts and unaffected by different hemolysis methods. RBC viability, defined as the ratio of the amplitude differential response during the passage of packed RBCs to that of the entire solution through the microfluidic detection channel in the SAW sensor, correlated strongly with results from a commercial UV spectrophotometer (UVS) after cryopreservation (R² = 0.99625). Under conditions with an 8:2 ratio of dead/live RBCs, the viability assessment rate of the SAW sensor reached approximately 5.1 × 10⁵ cells/s. The limit of detection for viable RBCs was 0.05 μL─a sensitivity unattainable by UVS─and the platform enabled on-chip separation of RBC ghosts from viable cells. These features collectively enable label-free, high-throughput, real-time, nondestructive viability assessment.