Bacteria and cancer cell pearl chain under dielectrophoresis.

In this work, we aim to observe and study the physics of bacteria and cancer cells pearl chain formation under dielectrophoresis (DEP). Experimentally, we visualized the formation of Bacillus subtilis bacterial pearl chain and human breast cancer cell (MCF-7) chain under positive and negative dielectrophoretic force, respectively. Through a simple simulation with creeping flow, AC/DC electric fields, and particle tracing modules in COMSOL, we examined the mechanism by which bacteria self-organize into a pearl chain across the gap between two electrodes via DEP. Our simulation results reveal that the region of greatest positive DEP force shifts from the electrode edge to the leading edge of the pearl chain, thus guiding the trajectories of free-flowing particles toward the leading edge via positive DEP. Our findings additionally highlight the mechanism why the free-flowing particles are more likely to join the existing pearl chain rather than starting a new pearl chain. This phenomenon is primarily due to the increase in magnitude of electric field gradient, and hence DEP force exerted, with the shortening gap between the pearl chain leading edge and the adjacent electrode. The findings shed light on the observed behavior of preferential pearl chain formation across electrode gaps.

Correction: Antibody-coated microstructures for selective isolation of immune cells in blood.

Correction for 'Antibody-coated microstructures for selective isolation of immune cells in blood' by Jiyu Li et al., Lab Chip, 2020, 20, 1072-1082, DOI: 10.1039/D0LC00078G.

Antibody-coated microstructures for selective isolation of immune cells in blood.

Cell isolation from blood is an important process for diagnosing immune diseases. There are still demands for a user-friendly approach to achieve high cell extraction efficiency and purity of a target immune cell subtype for more promising diagnosis and monitoring. For selective immune cell isolation, we developed a microstructured device, which consists of antibody-coated micropillars and micro-sieve arrays, for isolating a target immune cell subtype from bovine blood samples. The focusing micropillars can guide immune cells flowing to the subsequent micro-sieves based on deterministic lateral shifts of the cells. The arrangement of these microstructures is characterized and configured for the maximal cell capture rate. Surface modification with a selected antibody offers selective cell capture in the micro-sieves based on the antigen-antibody reaction. We prepare a cell mixture of human CD14-expressing leukemia cells (THP-1) and epithelial cells (MDA-MB-231) in diluted blood to characterize the cell isolation operation, with a selective cell isolation yield of >80%, cell purity of ∼100% and cell viability of >93%. Together, this microstructured device strategy can achieve high-yield selective isolation of immune cells from blood samples and support downstream genetic and biochemical cell analyses, contributing to the medical diagnosis of a broad range of immune diseases.