High resolution bacterial separation from blood using elasto-inertial
microfluidics
Abstract
Improved sample preparation has the potential to address a huge unmet
need for fast turnaround sepsis tests that enable early administration
of appropriate antimicrobial therapy. In recent years, inertial and
elasto-inertial microfluidics-based sample preparation has gained
substantial interest for bioparticle separation applications. However,
for applications in blood stream infections the throughput and bacteria
separation efficiency has thus far been limited. In this work, for the
first time we report elasto-inertial microfluidics-based bacteria
isolation from blood at throughputs and efficiencies unparalleled with
current microfluidics-based state of the art. In the method,
bacteria-spiked blood sample is prepositioned close to the outer wall of
a spiral microchannel using a viscoelastic sheath buffer. The blood
cells will remain fully focused throughout the length of the spiral
channel while bacteria migrate to the inner wall for effective
separation. Initially, microparticles were used to investigate particle
focusing and the separation performance of the spiral device. A
separation efficiency of 96% for the 1 µm particles was achieved, while
100% of 3 µm particles were recovered at the desired outlet at a
throughput (sample + sheath) of 1 mL/min. Following, processing blood
samples revealed a minimum of 1:2 dilution was necessary to keep the
blood cells fully focus at the outer wall. In experiments involving
bacteria spiked in diluted blood, viable E.coli were continuously
separated at a total flow rate of 1 mL/min, with a separation efficiency
between 82 to 90% depending on the blood dilution. Using a single
spiral, it takes 40 minutes to process 1 mL of whole blood at a
separation efficiency of 82% and 3 hr at 90% efficiency. To the best
of our knowledge, this is the highest bacteria separation efficiency
from blood sample reported using inertial and elasto-inertial methods.
As such, the label-free, passive high efficiency and high throughput of
bacteria isolation method has a great potential for speeding up
downstream phenotypic and molecular analysis of bacteria.