Picoliter droplets to mimic the chemical environment within cells

A cell is the common unit structure shared by all living organisms. But even simple prokaryotic cells are extremely complex chemical reactors, and we do not fully understand the basic underlying physical organic chemistry of the cell and we do not have a model system suitable for systematic studies. It is the broad aim of this research to construct a robust experimental platform to elucidate the precise influence that the particular physiochemical conditions commonly found in living systems have on model complex biochemical reactions. Monodisperse water-in-oil microdroplets, ~10-100um in diameter and surrounded by a monolayer of surfactant, allow for reactions to be studied systematically on a minute scale under idealized conditions. Droplets can be formed, fused, split, sorted and interrogated using fluorescence spectroscopy at kHz rates in microfluidic devices. The work is broadly divided into two main research projects and supported by technological developments in droplet manipulation and characterization. The first project will mimic prokaryotic cells and study the influence of global physical parameters on the in vitro transcription and translation (IVTT) of fluorescent proteins arising from a single copy of plasmid DNA in the droplets. A key part of this project will be the measurement of the level of noise present in the IVTT system (or level of fluctuations in rate of protein formation) and the influence of the physical environment on this noise. The second project aims to extend our approach to mimic eukaryotic cells, where a gel bead in a droplet represents the nucleus. In the first part of this project we will study communication between this cytoplasm and the co-compartmentalized bead containing DNA. To bridge the biochemical systems with more synthetic systems chemistry schemes, we also aim to study communications between trapped droplets, and emerging complexity in reaction diffusion networks that develop between droplet compartments.