A lab-on-a-chip for free-flow electrophoretic preconcentration of viruses and gel electrophoretic DNA extraction

Abstract

Nucleic acid amplification techniques such as real-time PCR are essential instruments for the identification and quantification of viruses. They are fast, very sensitive and highly specific, but often require elaborate and labor intensive sample preparation to achieve successful amplification of the target sequence. In this work we demonstrate the complete microfluidic preparation of amplifiable virus DNA from dilute specimens. Our approach combines free-flow electrophoretic preconcentration of viral particles with thermal lysis and gel-electrophoretic nucleic acid extraction on a single device. The on-chip preconcentration achieves a capture efficiency of >99% for dilute suspensions of bacteriophage PhiX174. Following preconcentration, phages are thermally lysed and released DNA is recovered after 40 s of on-chip gel-electrophoresis with a recovery rate of ∼73%. Furthermore we demonstrate a detection limit of ∼1 PFU ml⁻¹ (∼0.02 DNA copies per μl) for the detection of bacteriophage PhiX174 by PCR. To simplify operation of the device, we describe the development of a custom-made chip holder as well as a compact peristaltic pump and power supply, which enable user-friendly operation with low risk of cross-contamination and high potential for automation in the field of point-of-care diagnostics.