A Sensor for the In-Flight Detection of Single Fluorescent Microbodies in Nanoliter Droplets

Single cell isolation is a crucial process step in many biological and pharmaceutical applications, as the number of technologies and assays for single cells is constantly rising. In this study, we propose a simple yet effective method for isolating single cells from a homogeneous solution. Therefore, we equip a high- throughput nano-dispenser system with a novel fluorescence-based in-flight cell detection sensor, which scans the dispensed droplets for the presence of a fluorescent cell on the fly. Based on initial studies on the dispensing physics, four different illumination and detection configurations of the sensor are presented and investigated. Finally, the system's performance in terms of detection rate, efficiency and process time is determined using cell-sized polystyrene microbeads as a reference standard. The results are very promising, as a 96-well plate is filled with single beads in under 60 seconds with a reproducible efficiency of more than 95%. Based on its generic design, the cell detection sensor is adaptable to virtually any low-volume dispenser, which is a major innovation over existing technologies.