Automatically Controlled Microfluidic System for Continuous Separation of Rare Bacteria from Blood

Abstract

Bloodstream infection by microorganisms is a major public health concern worldwide. Millions of people per year suffer from microbial infections, and current blood culture-based diagnostic methods are time-consuming because of the low concentration of infectious microorganisms in the bloodstream. In this study, we introduce an efficient automated microfluidic system for the continuous isolation of rare infectious bacteria (Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa) from blood. Bacteria received a balanced force between a fluidic drag force and a periodically controlled dielectrophoretic (DEP) force from tilted electrodes to minimize cell adhesion to the electrodes, which prevented the loss of rare infectious bacteria. Target bacteria were efficiently segregated from the undesired blood cells to ensure that only the bacteria received the DEP force under the hypotonic condition, while the blood cells received no DEP force and exited the channel via a laminar flow. Thus, the bacteria were successfully extracted from the blood with a high recovery yield of 91.3%, and the limit of the bacteria concentration for isolation was 100 cfu/ml. We also developed an automated system that performed every step from blood-sample loading to application of electricity to the microfluidic chip for bacteria separation. It reduced the standard deviation of the bacteria recovery yield from 6.16 to 2.77 compared with the conventional batch process, providing stable bacteria-extraction performance and minimizing errors and bacteria loss caused by user mistakes.