Abstract
Deterministic lateral displacement (DLD) is a well-known microfluidic technique for particle separation with high potential for integration into bioreactors for therapeutic applications. Separation is based on the interaction of suspended particles in a liquid flowing through an array of microposts under low Reynolds conditions. This technique has been used previously to separate living cells of different sizes but similar shapes. Here, we present a DLD microchip to separate rod-shaped bacterial cells up to 10 µm from submicron spherical minicells. We designed two microchips with 50 and 25 µm cylindrical posts and spacing of 15 and 2.5 µm, respectively. Soft lithography was used to fabricate polydimethylsiloxane (PDMS) chips, which were assessed at different flow rates for their separation potential. The results showed negligible shear effect on the separation efficiency for both designs. However, the higher flow rates resulted in faster separation. We optimized the geometrical parameters including the shape, size, angle and critical radii of the posts and the width and depth of the channel as well as the number of arrays to achieve separation efficiency as high as 75.5% on a single-stage separation. These results pave the way for high-throughput separation and purification modules with the potential of direct integration into bioreactors.
Highlights
Deterministic lateral displacement (DLD) post arrays are an efficient tool to separate and enrich micrometer-scale particles, such as parasites, bacteria, blood cells and circulating tumor cells in blood [1–4]
To separate minicells from parental cells in the bacterial cell solution, two sets of experiments were run with Chip A along with a corresponding control experiment
Higher flow rates allow for faster real-time purification, which would be advantageous in applications where throughput is critical
Summary
Deterministic lateral displacement (DLD) post arrays are an efficient tool to separate and enrich micrometer-scale particles, such as parasites, bacteria, blood cells and circulating tumor cells in blood [1–4]. Discovered 50 years ago, minicells, spherical particles arising from aberrant asymmetric bacterial cell division events, have recently been exploited as model systems to visualize molecular machines in situ, due to their smaller size and other unique properties [5]. They provide a springboard for in-depth structural studies of bacterial macromolecular complexes and offer a unique approach for gaining novel structural insights into many important processes in microbiology [6]. Like their parental cells, they contain membranes, RNAs and proteins but no chromosome; they cannot divide or grow.
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