On-site extraction and purification of bacterial nucleic acids from blood samples using an unpowered microfluidic device

Abstract

Molecular diagnostics is a powerful technique for detecting pathogens with high sensitivity, but it has complicated sample preparation procedures that rely not only on a manual operation by experts but also on bulky equipment. Here, we report the use of an unpowered, microfluidic sample preparation device in on-site molecular diagnosis without the necessity of expertise and electrical devices. The device is assembled with two units, a plasma separation chip, and a nucleic acid extraction and purification chip. As a model pathogen, Escherichia coli (E. coli) O157:H7 was first separated from the blood sample using the unpowered plasma separation chip, and then the DNA was extracted and purified from the separated bacteria by using the finter-actuated nucleic acid extraction and purification chip. 103 to 108 CFU/mL of E. coli O157:H7 was infiltered from the blood sample with ∼1% of permeation efficiency. The extracted DNA was successfully purified and confirmed by gel electrophoresis after the polymerase chain reaction. This unpowered sample pretreatment method is precise and reliable, even at low concentrations of down to 103 CFU/mL of E. coli in the blood sample.