Optimizing flow dynamics for medical wires captures cells more efficiently for diagnostics

Isolating tumor cells from the blood is important for cancer diagnostics, but only very low numbers of tumor cells, fewer than 1:10¹⁰, are in circulation. One new technique involves placing a wire, modified with appropriate capture antibodies, into the bloodstream to capture the tumor cells for genome analysis. However, this requires extremely efficient cell capture. Chemical physicists conducted an analysis that enhances the contact probability of this system and report their findings in Biomicrofluidics.

When such a wire is placed in the bloodstream, blood typically flows past in a laminar fashion with minimal contact between the wire and blood cells. The researchers investigated twisted wire profiles to create obstacles that induce cross flows and mixing, which increases the likelihood of cell contact with the wire. The authors drew on both theoretical and experimental methods to assess the influence of wire geometries such as different torsions, diameters and varying cross-sectional shape profiles on the number of surface contacts.

Simple dynamic fluid simulations modeled wires in a capillary with blood flows of varying velocity. The model also calculated induced cross flows and the number of particles that came into contact with the wire. In model experiments, wires were chemically coated to specifically recognize the biotinylated polystyrene microparticles, mimicking cells of interest, that flowed past.

“Through a simple geometry optimization we saw an 80-times higher probability of catching cell-sized particles than with the simple wire,” said co-author Jürgen Rühe. “There is still room for improvement.” Validation studies are planned next before these optimized wires can be used in clinical practice.

Source: “Geometrically enhanced sensor surfaces for the selective capture of cell-like particles in a laminar flow field,” by Frank D. Scherag, Thomas Brandstetter, and Jürgen Rühe, Biomicrofluidics (2018). The article can be accessed at https://doi.org/10.1063/1.5017714 .