The emerging antibiotic-resistant bacteria (ARB) have led to increased treatment costs for patients, longer hospitalization, and much higher rates of morbidity and mortality. Rapid detection of infecting strains, especially ARB, is critical for the effect treatment of bloodstream infections. In this work, we introduce an integrated microfluidic nano-sieve device for rapid and centrifuge-free bacteria isolation from whole blood. The RBCs that may clog the device are first depleted by a magnetic bead-based immunoassay. This process makes the sample less viscous without losing the bacteria. Then, the sample was pumped into a microbead (5 µm and 10 µm) patterned nano-sieve device. The small spacing between microbeads trapped the bacteria and allowed the human plasma to be filtered out. A pneumatic chamber was added on top of the nano-sieve and efficiently reduces the microbead/bacteria loss. The pneumatic regulated nano-sieve device is shown in Figure 1. The RBC depletion unit consists of multiple inlets and a magnet. The stained bacteria showed strong fluorescent signal, illustrating that most of them were trapped by in the nano-sieve (Figure 2a). A trapping efficiency of over 75% was achieved by comparing the bacteria concentration before and after nano-sieve capture (Figure 2b). This integrated system allows rapid bacteria isolation but does not require bulky instruments such as a centrifuge, paving ways for multiplexing, labor-free, and efficient pathogen separation for numerous diagnostic applications.

<b>Figure 1</b>: Exploded (a) and assembled (b) pneumatic regulated nano-sieve for bacteria isolation.

Figure 1: Exploded (a) and assembled (b) pneumatic regulated nano-sieve for bacteria isolation.

<b>Figure 2:</b> (a) Distribution of trapped bacteria under various low magnifications. The white arrow indicates the flow direction and the yellow dashed line shows the region of 5 µm microbeads. The red dashed line is the interface of different sizes of microbeads. (b) Bacteria density before (b-i) and after (b-ii) nano-sieve filtering.

Figure 2: (a) Distribution of trapped bacteria under various low magnifications. The white arrow indicates the flow direction and the yellow dashed line shows the region of 5 µm microbeads. The red dashed line is the interface of different sizes of microbeads. (b) Bacteria density before (b-i) and after (b-ii) nano-sieve filtering.

Nicole Hill

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