Synergistic use of electroosmotic flow and magnetic forces for nucleic acid extraction

Abstract

Nucleic acid sample preparation is essential for biological sample-based diagnostics. It is crucial that diagnostic tests be both specific and sensitive as to provide the most accurate diagnosis possible. Inefficient sample preparation can hinder the specificity and sensitivity of these tests since carryover contaminants can inhibit downstream processes, such as amplification. Microfluidic devices have been used previously to extract nucleic acids from a biological sample due to lower reagent volumes and ease of use. A novel microfluidic chip has been designed for nucleic acid sample preparation which combines electroosmotic flow and magnetic bead-based extraction to isolate DNA from a plasma sample. A steady electric field was incorporated into the microfluidic chip design, which when combined with a glass clover slip and a voltage differential, creates electroosmotic flow. With the goal of isolating nucleic acids into a clean, inhibitor free solution, the electroosmotic flow is the driving force and separation mechanism purifying the DNA sample captured on magnetic beads in the microfluidic chip system. Carryover volume, or the volume of unwanted sample contaminants that accompany the nucleic acids into the final elution buffer, was minimized to 0.22 ± 0.03%. In combination with magnetic bead based nucleic acid extraction techniques, a 15% increase in DNA extraction yield is reported for the microfluidic chip with the voltage applied versus without. Although the literature on nucleic acid separation in microfluidic chips is abundant, this is the first to combine microfluidic chip design, magnetic bead-based isolation and electroosmotic flow.