Nanodroplet-based reagent delivery into water-in-fluorinated-oil droplets

In vitro compartmentalization is a technique for generating water-in-oil microdroplets to establish the genotype (DNA information)-phenotype (biomolecule function) linkage required by many biological applications. Recently, fluorinated oils have become more widely used for making microdroplets due to their better biocompatibility. However, it is difficult to perform multi-step reactions requiring the addition of reagents in water-in-fluorinated-oil microdroplets. On-chip droplet manipulation is usually used for such purposes, but it may encounter some technical issues of low throughput or time delay of reagent delivery into different microdroplets. Hence, to address the above issues, we evaluated the feasibility of employing a nanodroplets-based approach for the delivery of copper ions and peptide molecules of middle-size (2 kDa).