Numerical Assessment of the Efficiency of a New Minimally Invasive Probe for the Isolation of Circulating Tumor Cells

Liquid biopsy, particularly the isolation of circulating tumor cells (CTCs) from blood, is a promising approach in the fight against cancer. However, the main reason why CTCs are hardly used as biomarkers in the clinic is their complicated isolation from the patient's blood. Existing ex vivo systems use a small volume of blood and can therefore only isolate very few CTCs. To overcome this problem and increase the number of isolated CTCs, a new in vivo method-the BMProbe was introduced, which can isolate CTCs directly from the patient's bloodstream. This study investigates the efficiency of the BMProbe by using Computational Fluid Dynamics simulations to evaluate parameters influencing the attachment probability of CTCs to the probe surface. The analyzed parameters include screened blood volume, residence time, and wall normal rate. Additionally, the impact of probe geometry, vein diameter, and blood flow velocity on probe efficiency was examined. The numerical data suggest that the geometry has a strong influence on cell binding efficiency. Increasing the number of windings from 4 to 32 improves the transport of cells to the surface (negative wall normal rate) from 0 to -29 [mm²/s] and the screened blood volume by 138% but decreases the residence time of particles in the close vicinity of the probe by 77%. When compared to experimental data, the screened blood volume and the wall normal rate indicate cell attachment very well, whereas the residence time does not show a significant impact on the attachment of cells. For the 32-windings BMProbe, the screened blood volume is determined to be 130-313 mL, depending on the vein diameter, which is a multiple of the volume achieved by common CTC isolation techniques.