Circulating Tumor Cells (CTCs), which are rare cancer cells that detach from a primary malignancy and infiltrate the circulatory system, are instrumental in the advancement of metastatic cancer. One of the most effective techniques for detecting and isolating CTCs from the bloodstream is inertial focusing through microfluidic devices. Because inertial microfluidics is a passive technique, no markers are required. In order to separate CTC from other blood cells, this technique makes use of the dimensional differences between the cells. In this work, CTCs are isolated from other blood cells using hydrodynamic force-based inertial microfluidics systems.

The current study assesses the effects of drag and inertial forces on cells of different sizes in serpentine microchannels with an internal radius of 800 μm and a curvature angle of 280°. The important feature of the microchannel structures is the different depths (60 μm, 73 μm, 90 μm and 105 μm) and different angles between the outlet channels (73 and 90 degrees). In the presented system, the best results were obtained by selecting a channel depth of 105 μm and an outlet channel angle of 73 degrees. These special microchannel geometries facilitate parallelization with optical detection and provide effective size-based separation of CTCs. The COMSOL Multiphysics 6.2 software was used to perform three-dimensional numerical simulations and estimated the paths taken by cells of different types in order to verify the performance of the microchannel designs. The simulation results were subsequently supported by experimental investigations employing polydimethylsiloxane (PDMS) microchannels with different configurations and sizes of cells. In relation to this study, the HeLa cell line was used as a CTC model, while the Jurkat and K-562 cell lines were used to mimic blood cells.

The results demonstrated that by employing hydrodynamic forces, the developed microfluidic device can isolate CTCs with high sensitivity. In accordance with the simulation results, an effective separation on the microfluidic chip led to the collection the CTCs with a success rate of over 90%. The performance of this system, which does not require external force and is label-free, is better and more effective than the majority of systems found in the literature.

This label-free approach provides a cost-effective way to monitor and detect early cancer, which will be helpful in clinical trials. Future research will focus on the improvement of microchannel design. Its suitability for different cancer types and clinical environments will be also explored.