Development and Characterization of a Microfluidic Device That Performs Gdna Extraction from Whole Blood Using Magnetic Beads

Genetic testing from various starting samples such as blood and saliva has become increasingly popular with the advent of next generation sequencing. These tests enable more personalized medicine but are limited by complicated workflow and sample-to-sample variations at the point-of-care (POC). New technologies must be developed that minimize complexity and cost of workflows while delivering high quality results.

Here, a simple, automated microfluidic-based system that performs genomic DNA (gDNA) extraction from whole blood was developed. To develop this system, reagents from the chemagic^TM DNA Blood250 Kit (PerkinElmer) were used on a microfluidic chip platform. To begin, a mixture of blood lysate, paramagnetic beads, and binding buffer are placed into the input well. Then the gDNA-bound paramagnetic beads are pulled using a magnet through a center channel containing a wash buffer to the output well containing elution buffer. The gDNA is eluted at 55^oC off the chip. This system uses minimal sample handling and equipment, while maintaining gDNA yield when compared to the manual chemagic^TMkit. gDNA quantification techniques including PCR, spectrofluorimetry, and electrophoresis were used to test the gDNA eluted from the chip following extraction.

Bead transport and molecular diffusional analysis were performed for optimization of gDNA elution. This revealed that above a critical mass (~10 nanograms), the gDNA-paramagnetic bead complex is unable to move through the center channel of the microfluidic chip. It was found that this is due to both the length of gDNA and interactions between gDNA molecules themselves, which cause the paramagnetic beads to aggregate, creating a bead-gDNA complex that behaves elastically when being pulled by the magnet. To further elucidate the parameters of the DNA-paramagnetic bead aggregate formed, this phenomenon will be mathematically modeled and tested. The microfluidic-based extraction of DNA from whole blood described here is paramount to future work in DNA-based POC diagnostics.