A critical early step in drug discovery is the screening of a chemical library. Typically, promising compounds are identified in a primary screen and then more fully characterized in a dose-response analysis with 7-10 data points per compound. Here, we describe a robust microfluidic approach that increases the number of data points to approximately 10,000 per compound. The system exploits Taylor-Aris dispersion to create concentration gradients, which are then segmented into picoliter microreactors by droplet-based microfluidics. The large number of data points results in IC 50 values that are highly precise ( 2.40% at 95% confidence) and highly reproducible (CV 2.45%, n 16). In addition, the high resolution of the data reveals complex dose-response relationships unambiguously. We used this system to screen a chemical library of 704 compounds against protein tyrosine phosphatase 1B, a diabetes, obesity, and cancer target. We identified a number of novel inhibitors, the most potent being sodium cefsulodine, which has an IC 50 of 27 0.83 μM.high-throughput screening | HTS | small molecule library I n the early 16th century the Swiss chemist Paracelsus declared "all substances are poisons, there is none which is not a poison; only the right dose makes a substance non-poisonous." This idea that the biological effects of a chemical compound are dependent upon its concentration was quantified by A. V. Hill in 1910 (1). However, despite the fact that compounds can display complex concentration-dependent relationships, varying in potency, efficacy, and steepness of response, usually just a single measurement at a single concentration (approximately 10 μM) is obtained for each compound in the chemical library during a primary drug screen, even when using state-of-the-art robotic microplate-based screening systems. This results in high numbers of false positives and false negatives (2), as well as the inability to identify subtle, complex pharmacology, such as partial agonism or antagonism. Even when dose-response curves are generated during a quantitative primary screen (3) or, more typically, during the follow-up of a single-point screen, the time and cost limitations mean that the curves typically contain only 7-10 data points each. With ≤10 nonduplicated data points, and as many as four adjustable nonlinear parameters (e.g., in the four-parameter Hill function), the results are highly sensitive to the data quality: For example, the presence of a single outlying data point can substantially alter the fit of the data, unless the outliers are identified and removed (4).We have developed a system that uses droplet-based microfluidics to generate high-quality dose-response data during drug screening. Droplet-based microfluidics is itself a new technology for creating and manipulating picoliter-volume aqueous droplets that function as independent microreactors (for a review see ref. 5). As a result of the miniaturization inherent in this approach, our system (Fig. 1) is capable of generating doseresponse curves at materiall...

Monoclonal antibodies can specifically bind or even inhibit drug targets and have hence become the fastest growing class of human therapeutics. Although they can be screened for binding affinities at very high throughput using systems such as phage display, screening for functional properties (e.g., the inhibition of a drug target) is much more challenging. Typically these screens require the generation of immortalized hybridoma cells, as well as clonal expansion in microtiter plates over several weeks, and the number of clones that can be assayed is typically no more than a few thousand. We present here a microfluidic platform allowing the functional screening of up to 300,000 individual hybridoma cell clones within less than a day. This approach should also be applicable to nonimmortalized primary B-cells, as no cell proliferation is required: Individual cells are encapsulated into aqueous microdroplets and assayed directly for the release of antibodies inhibiting a drug target based on fluorescence. We used this system to perform a model screen for antibodies that inhibit angiotensin converting enzyme 1, a target for hypertension and congestive heart failure drugs. When cells expressing these antibodies were spiked into an unrelated hybridoma cell population in a ratio of 1∶10,000 we observed a 9,400-fold enrichment after fluorescence activated droplet sorting. A wide variance in antibody expression levels at the single-cell level within a single hybridoma line was observed and high expressors could be successfully sorted and recultivated.

SARS-CoV-2 is a novel virus that has rapidly spread, causing a global pandemic. In the majority of infected patients, SARS-CoV-2 leads to mild disease; however, in a significant proportion of infections, individuals develop severe symptoms that can lead to long-lasting lung damage or death. These severe cases are often associated with high levels of pro-inflammatory cytokines and low antiviral responses, which can cause systemic complications. Here, we have evaluated transcriptional and cytokine secretion profiles and detected a distinct upregulation of inflammatory cytokines in infected cell cultures and samples taken from infected patients. Building on these observations, we found a specific activation of NF-κB and a block of IRF3 nuclear translocation in SARS-CoV-2 infected cells. This NF-κB response was mediated by cGAS-STING activation and could be attenuated through several STING-targeting drugs. Our results show that SARS-CoV-2 directs a cGAS-STING mediated, NF-κB-driven inflammatory immune response in human epithelial cells that likely contributes to inflammatory responses seen in patients and could be therapeutically targeted to suppress severe disease symptoms.