Integrated micromixer for incubation and separation of cancer cells on a centrifugal platform using inertial and dean forces

Abstract

In this article, we demonstrate for the first time the integration of a micromixer unit for the creation of a cancer cell–microbead complex, and an inertial flow unit for the detection and separation in a centrifugal platform. The two units work under different operational principles but both exploit the centrifugal pseudo-force. The units achieve a high level of binding efficiency and a mechanism for cell sorting and guiding with the established asymmetric inertial flow system, respectively. The design of the passive micromixer takes advantage of the centrifugal force in an orthogonal direction to create what has been termed “flipping” to increase chaotic advection in the unit by turning the microchannel contents 180° at each turn. Blood was spiked into the system to identify maximum operational range. In non-spiked samples, cancer cells (MCF7) and microbeads bind together to generate cell–bead complexes (MCF7-PS) with a binding efficiency of 97.1 %; however, blood-spiked samples of 2 % v/v blood content were found to have a separation of 92.5 %, which diminished further with increasing blood content (5 % v/v blood). Once the complexes enter the inertial flow unit under these conditions, it remains in high operational flow-focusing standard with up to 98.7 % ± 1.4 of the introduced cancer cells reaching the designated outlet; for both units, unpaired statistical t tests show P < 5 with 95 % confidence level. This integration allows for the positive detection of cancer cells with reactive epitopes while the increased complex averaged size of cancer cell–microbeads standardizes the flow rate required for size-based flow-focusing. It can also be optimized for negative selection or multivariate detection of different cell biomarkers by enhancing sedimentation forces.