Abstract
This study demonstrates the suitability of microfluidic structures for high throughput blood cell analysis. The microfluidic chips exploit fully integrated hydrodynamic focusing based on two different concepts: Two-stage cascade focusing and spin focusing (vortex) principle. The sample—A suspension of micro particles or blood cells—is injected into a sheath fluid streaming at a substantially higher flow rate, which assures positioning of the particles in the center of the flow channel. Particle velocities of a few m/s are achieved as required for high throughput blood cell analysis. The stability of hydrodynamic particle positioning was evaluated by measuring the pulse heights distributions of fluorescence signals from calibration beads. Quantitative assessment based on coefficient of variation for the fluorescence intensity distributions resulted in a value of about 3% determined for the micro-device exploiting cascade hydrodynamic focusing. For the spin focusing approach similar values were achieved for sample flow rates being 1.5 times lower. Our results indicate that the performances of both variants of hydrodynamic focusing suit for blood cell differentiation and counting. The potential of the micro flow cytometer is demonstrated by detecting immunologically labeled CD3 positive and CD4 positive T-lymphocytes in blood.
Highlights
Mass production of microsystems has the potential to provide low-cost, disposable chips for complex cellular-based analyses including fundamentally new approaches
Microfluidic devices were fabricated using ultraprecision milling followed by hot embossing in transparent thermoplastic
To maintain the same flow rate in both microfluidic chips, pressure was higher for the spin focusing chip, i.e., 600 mbar versus 360 mbar for the cascade chip
Summary
Mass production of microsystems has the potential to provide low-cost, disposable chips for complex cellular-based analyses including fundamentally new approaches. Flow cytometry has a number of applications, e.g., in microbiology and marine biology, but it is mostly applied in laboratory medicine, in particular for differentiation and counting of blood cells [8]. This type of application was demonstrated in a number of microchips [1,3,5,9,10,11,12,13,14,15]. Numerous commercial solutions show that such technology could establish the basis for simple and robust analytical systems being of particular relevance for point-of-care in vitro diagnostics with a wide range of applications in emergency medicine and intensive care. The main efforts made in this field, are focused to assure functionality which is comparable if not superior to conventional, large frame flow cytometric systems
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