Isosceles Trapezoidal Spiral Microchannel for Separation of Large particles and Giant Cancer cells

Background: Polyploid giant cancer cells (PGCCs) contribute to the genetic heterogeneity and evolution of tumor cells. To study these cells, they need to be separated from tumor cell populations. However, due to their large size it is challenging to isolate them. Currently used methods, such as fluorescence-activated cell sorting (FACS) require fluorescent labeling which impedes reliable downstream analysis and removal of PGCCs. Results: This study solves this impediment by separating the PGCCs by applying an isosceles trapezoidal spiral microchannel (ITSμC), which maximizes the Dean drag force ( F D ) and increases the separation distance between particles through identical vortices. Numerical simulations showed that the ITSμC generated a stronger F D than either rectangular or trapezoidal channels. Experimental results confirmed that the ITSμC aligned large polystyrene (PS) particles (50 μm in average diameter) close to the inner wall, while small PS particles (23 μm in average diameter) were aligned close to the outer wall of the channel. Using the ITSμC, we successfully isolated PGCCs from doxorubicin-resistant triple-negative breast cancer (DOXR-TNBC) cells, including normal-sized cells, with high purity (> 90%), yield (> 90%), and viability (> 90%) at high flow rates (3-4 mL/min) in both cultured and clinical samples. Conclusion: The ITSμC can be used to separate large rare cells, such as PGCCs, without fluorescent labeling and can be applied to downstream analysis when cells need to be cultured after separation. The generality of the ITSµC methodology makes it a potential method for other heterogeneous cell populations as well as other nano-sized particles.