Description of Detection & Separation

Code	MP26
Track	Detection & Separation
Title	Microchip DNA Extraction with Magnetically-controlled Silica Beads in an Unpacked Glass Microchip
Author	Gabriela Duarte, M.D.
Co-Authors	Carol W. Price*, Emanuel Carrilho and James P. Landers,* University of Sao Paulo, Institute of Chemistry of Sao Carlos Department of Chemistry, University of Virginia Charlottesville, VA 22904 USA ** Departments of Pathology and Mechanical Engineering, University of Virginia, Charlottesville, VA 22904 USA
Abstract	Efficient and reliable DNA extraction is a critical step for biomedical and clinical research and for clinical diagnostics. Methods for microchip-based solid phase extraction (µSPE) of DNA using silica adsorption under chaotropic conditions have been described. This report describes the development of a method for DNA extraction using the same silica chemistry but utilizing a mobile solid phase rather than a packed microfluidic channel or stationary substrate. Roughly 300,000 MagneSil paramagnetic particles, iron-cored silicon dioxide coated magnetic beads, are loaded into a microfluidic channel measuring 15 mm (l) x 1 mm (w) x 0.2 mm (d) and exposed to an external magnetic field. The continuous movement of the beads in the magnetic field improves the efficiency of DNA binding by insuring thorough mixing of the relatively small number of beads with the entire sample. Following adsorption, residual sample is washed from the beads with isopropyl alcohol and the DNA is eluted with a Tris-EDTA buffer using the magnetic field. Extraction experiments show that DNA bound to the beads can be extracted with high efficiency, whether the starting sample is simple (pre-purified DNA, ~60% extraction efficiency) or complex (fresh human whole blood, ~70% extraction efficiency). Purified DNA can be extracted in as little as 12 minutes. In addition, the DNA extracted using this method is PCR amplifiable, making this a viable technique for isolating DNA for downstream sample analysis on the same microdevice.