Cell-free fetal DNA (cffDNA) extraction from whole blood by using a fully automatic centrifugal microfluidic device based on displacement of magnetic silica beads

The purpose of this research was to design a fully automated centrifugal microfluidic system (Lab-on-a-Disk) for isolating cell free fetal DNAs (cffDNAs) from whole blood. To achieve this goal, magnetic silica beads were used, such that after attaching cffDNA to them, they were transferred between chambers by using external fixed magnets. All the standards and required steps for cffDNA extraction including plasma separation, adding proteinase K, lysis buffer, binding buffer, washing buffer, and elution buffer were considered in this designed disk. To evaluate the function of the disk, the collected samples were tested from several aspects. First, the purity of extracted plasma from whole blood was investigated which included hemoglobin test, hemocytometer, etc. This disk could extract 1.3 mL pure plasma from 3 mL blood with 45% hematocrit. The results of the extracted plasma showed 99% purity. Finally, the cffDNAs were examined by using a male fetal gender identification kit and real-time PCR machine. The results indicated the correct function of the disk in extracting cffDNAs in samples of 10 Landa from cycle 34 onwards. Compared to the clinical method, the disk not only was able to extract cffDNA in 20 min but also it led to less buffer consumption since the disk only required 1 mL plasma for extraction of cffDNAs.