(P-QU-11) Residual WBC Count Using Image-Based Immunofluorescence Cell Counter with Microfluidic Concentration Chip

Background/Case Studies: Accurate measurement of residual white blood cells (WBCs) is essential for quality control in leukoreduced blood components. Conventional methods such as the Nageotte chamber and flow cytometry are reliable but labor-intensive, time-consuming, and costly. These drawbacks limit their use in high-throughput or resource-limited settings. We evaluated a novel system combining the Microscanner C3—an image-based immunofluorescence cell counter—with a microfluidic concentration chip to enhance detection sensitivity and workflow efficiency.

Study

Design/Methods:
Microfluidic Chip Design:
The microfluidic concentration chip was fabricated using soft lithography with PDMS material and SU-8 photoresist molds. The main channel (50 μm wide, 25 μm high) and an expansion zone (700 μm wide) were designed to optimize leukocyte flow and enrichment. To reduce non-specific protein binding, channel surfaces were treated with Triton X-100. A hyaluronic acid-based viscoelastic solution was used to maintain stable flow characteristics.

Red cell concentrates were serially diluted using leukoreduced RBCs and normal saline to prepare WBC concentrations of 200, 50, 25, 7.8, 1.9, and 0.5 WBCs/μL. The samples were stained with PI lysis solution (Biozentech, Korea) and analyzed using the Microscanner C3 equipped with the microfluidic concentration chip.
The performance of the system was evaluated for repeatability, linearity, limit of detection (LOD), and precision. Results were compared to the Nageotte chamber method and flow cytometry (Navios EX, Beckman Coulter; LeucoCOUNT, BD Biosciences).



Results/Findings: Residual WBC counting with the Microscanner C3 and microfluidic chip was completed within 5 minutes. The chip efficiently concentrated WBCs from the diluted samples. Linearity was maintained across a range of 0.5–200 WBCs/μL (R² > 0.92 vs. flow cytometry), and correlation with Nageotte counting was R² > 0.94. The coefficient of variation ranged from 9.4% to 18.7% (25–200 WBCs/μL). The system’s detection limit reached 0.5 WBCs/μL using saline-diluted samples.



Conclusions: The Microscanner C3 integrated with a microfluidic concentration chip enables rapid, reproducible, and cost-effective residual WBC quantification. This platform is well-suited for quality control in blood component manufacturing, particularly in settings with limited access to advanced cytometry systems.