For a long time, artificial RNAs have been developed by in vitro selection methodologies like Systematic Evolution of Ligands by EXponential enrichment (SELEX). Yet, even though this technology is extremely powerful to isolate specific and high-affinity binders, it is less suited for the isolation of RNAs optimized for more complex functions such as fluorescence emission or multiple-turnover catalysis. Whereas such RNAs should ideally be developed by screening approaches, conventional microtiter plate assays become rapidly cost-prohibitive. However, the advent of droplet-based microfluidics recently enabled us to devise microfluidic-assisted In Vitro Compartmentalization (μIVC), a strongly miniaturized and highly parallelized screening technology allowing to functionally screen millions of mutants in a single day while using a very low amount of reagent. Used in combination with high-throughput sequencing, the resulting μIVC-seq pipeline described in this chapter now allows rapid and semiautomated screening to be performed at low cost and in an ultrahigh-throughput regime.
Keywords: Artificial RNAs; Directed evolution; Droplet microfluidics; Functional screening; In vitro selection; RNA.