In recent decades, scientific interest in the development of devices capable of performing routine clinical analyses through the application of standardized traditional laboratory protocols in a miniaturized lab-on-a-chip device has increased. In the present work, an innovative microdevice for the on-line whole blood dilution with a phosphate buffer solution (PBS) and separation of plasma was designed, manufactured, and characterized. The microdevice was constructed with a rectangular cross-section and spiral-shaped microchannels by photolithography and soft litography. Also, the widths of the diluted plasma and the remaining blood outlet microchannels were different to create a difference in the outlet flow rates to facilitate and achieve the plasma separation based on the combination of centrifugal effect (Dean drag force) and bifurcation law (Zweifach-Fung effect). The separation purity (α) under the separation conditions (total flow rates between 25 and 100 μL/min, entrance flow rate ratio PBS/whole blood between 4 and 10, and hematocrit (% HCT) between 3 and 8) was around 100% for fresh blood samples, while the separation efficiency (β) was between 8 and 13%. The concentration in the separated diluted plasma was between 0.1 and 0.7% (v/v) with plasma flow rates between 3 and 7 μL/min, respectively. The quality of the diluted and separated plasma from micordevice was corroborated from a blood sample from a patient diagnosed with rheumatoid arthritis through the quantification of anti-cyclic citrullinated peptide (anti-CCP) antibodies employing a microdevice immunoassay. The developed microdevice has a high potential to be coupled with the on-line detection of biomarkers.
Keywords: Microfluidics; On-line dilution; Plasma; Separation.
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