Developing an Artificial Cell-On-A-Chip Image Credit: Billion Photos / Shutterstock.com How can the exchange of energy and materials be replicated in a cell-on-a-chip? In the living cell, the biochemical reactions which occur are maintained in a “steady state” by the exchange of energy and materials with the surrounding environment. Generally, in vitro systems do not utilize this exchange, therefore these systems will reach chemical equilibrium, and make it difficult to investigate complex biochemical networks that occur within a cell. To address this, Niederholtmeyer and co. created a system for gene expression using a microfluidic system to create a cell-on-a-chip. The system was based on nanoliter-sized microfluidic reactors. Into this system, a mixture containing the necessary components for gene expression was added in dilution steps, alongside the template DNA. This lead to the displacement of the fluid that was already present in the system. Fluorescence labeling was used to determine the amount of DNA, RNA and protein present in the system. This cell-on-a-chip was able to maintain steady-state gene expression for around 30 hours.