ABSTRACT Cell secretions are fundamental to biological processes, biotechnology, and cell therapies. The ability to analyze and select out single cells based on secretions is particularly critical for the rapid development of monoclonal antibody therapies. This need was highlighted recently with respect to the COVID-19 pandemic. Distributed capabilities to screen and sort B-cells, hybridoma cells, and producer cells (e.g CHO) based on quantitative secretion phenotype can accelerate the discovery and development of therapeutic neutralizing antibodies and aid in production of antigenic proteins for vaccine development. A key challenge is the screening of producer cell lines for productivity, which can take months and require significant manual intervention. Emphasizing the critical need, several microfluidic platforms have been developed for the automated screening of antibody secreting cells. However, these systems require specialized expertise or commercial equipment that is not widely available, and the number of cells that can be analyzed remains small. Thus, there is a critical need for high- throughput cell screening workflows that do not rely on new capital equipment. To address this bottleneck, Partillion plans to transition a lab-on-a-particle technological breakthrough, highlighted as the SLAS Innovation Award winner in 2020, into our first reagent product that enables customers to use their standard flow sorter machines for the selection of producer cell lines that secrete antibodies and other recombinant products. Our technology is based on microscale crescent-shaped hydrogel nanovials which capture cells, are functionalized to capture secretions, and template the formation of millions of uniform drops within seconds, all with simple pipetting and centrifugation steps. These drops prevent the loss and cross-talk of secretions. Particles and associated cells can then be sorted with flow cytometers based on the amount of secreted product at much higher rates than current techniques. In this Phase I SBIR, we will engineer and validate our reagent-based product to work robustly with antibody producing CHO cell lines. We will develop workflows for compatibility on a number of standard, commercially available flow cytometers in order to ensure ease of adoption by a wider customer base. We will also increase single-cell loading efficiency of the nanovials, beating Poisson-governed loading by 30-fold, to reduce the number of cell doublets and increase throughput in order to be able to screen larger populations for rarer or more high-producing clones in a single run. At the completion of the proposed work we will have demonstrated the ability to sort through > 1 million clones in a work day, orders of magnitude higher than current technologies. Successful completion of our project will result in reagents with immediate impact in enabling distributed development and production of antibodies for diagnostic and therapeutic purposes.