The applications of serology tests to the virus SARS-CoV-2 are diverse, ranging from diagnosing COVID-19, understanding the humoral response to this disease, estimating its prevalence in a population, to modeling...

New tools that facilitate the study of cell-to-cell variability could help uncover novel cellular regulation mechanisms. We present an integrated microfluidic platform to analyze a large number of single cells in parallel. To isolate and analyze thousands of individual cells in multiplexed conditions, our platform incorporates arrays of microwells (7 pL each) in a multilayered microfluidic device. The device allows the simultaneous loading of cells into 16 separate chambers, each containing 4640 microwells, for a total of 74 240 wells per device. We characterized different parameters important for the operation of the microfluidic device including flow rate, solution exchange rate in a microchamber, shear stress, and time to fill up a single microwell with molecules of different molecular weight. In general, after ∼7.5 min of cell loading our device has an 80% microwell occupancy with 1-4 cells, of which 36% of wells contained a single cell. To test the functionality of our device, we carried out a cell viability assay with adherent and nonadherent cells. We also studied the production of neutrophil extracellular traps (NETs) from single neutrophils isolated from peripheral blood, observing the existence of temporal heterogeneity in NETs production, perhaps having implications in the type of the neutrophil response to an infection or inflammation. We foresee our platform will have a variety of applications in drug discovery and cellular biology by facilitating the characterization of phenotypic differences in a monoclonal cell population.

Integrated platforms for automatic assessment of cellular functional secretory immunophenotyping could have a widespread use in the diagnosis, realtime monitoring, and therapy evaluation of several pathologies. We present a microfluidic platform with integrated biosensors and culture chambers to measure cytokine secretion from a consistent and uniform number of immune cells. The biosensor relies on a fluorescence sandwich immunoassay enabled by the mechanically induced trapping of molecular interactions method. The platform contains 32 cell culture chambers, each patterned with an array of 492 microwells, to capture and analyze both adherent and nonadherent immune cells. Multiple stimuli can be delivered to a set of culture chambers. Per chamber, we were able to capture consistently 1113 ± 191 of blood-derived monocytes and neutrophils and 348 ± 37 THP-1 monocytes. Good occupancy efficiencies of ∼70% with a uniformity of ∼90% across all of the culture chambers of the device were achieved. Furthermore, we demonstrate that up to 96% of cells remain viable for the first 48 h. The employment of epoxy-modified glass substrates and active mixing enhanced the biosensing performance compared to the use of bare glass and simple diffusion. Finally, we performed functional secretory analysis of interleukin-8 and tumor necrosis factor alpha from human neutrophils and monocytes, stimulated with various doses of lipopolysaccharide and phorbol 12-myristate 13-acetate−ionomycin, respectively. We foresee the employment of our microfluidic platform in the diagnosis of different pathologies where alterations in cytokine secretion patterns can be used as biomarkers.