We report the development of a microfluidic array device for continuous-exchange, cell-free protein synthesis. The advantages of protein expression in the microfluidic array include (1) the potential to achieve high-throughput protein expression, matching the throughput of gene discovery; (2) more than 2 orders of magnitude reduction in reagent consumption, decreasing the cost of protein synthesis; and (3) the possibility to integrate with detection for rapid protein analysis, eliminating the need to harvest proteins. The device consists of an array of units, and each unit can be used for production of an individual protein. The unit comprises a tray chamber for in vitro protein expression and a well chamber as a nutrient reservoir. The tray is nested in the well, and they are separated by a dialysis membrane and connected through a microfluidic connection that provides a means to supply nutrients and remove the reaction byproducts. The device is demonstrated by synthesis of green fluorescent protein, chloramphenicol acetyl-transferase, and luciferase. Protein expression in the device lasts 5-10 times longer and the production yield is 13-22 times higher than in a microcentrifuge tube. In addition, we studied the effects of the operation temperature and hydrostatic flow on the protein production yield.

In this work we present a novel thermal bonding method for thermoplastic microfluidic devices. This simple method employs a modified vacuum bagging technique, a concept borrowed from the aerospace industry, to produce conventional thick substrate microfluidic devices, as well as multi-layer film devices. The bonds produced using this method are superior to those obtained using conventional thermal bonding methods, including thermal lamination, and are capable of sustaining burst pressures in excess of 550 kPa. To illustrate the utility of this method, thick substrate devices were produced, as well as a six-layer film device that incorporated several complex features.

Cell-free protein synthesis (CFPS) is an alternative approach to cell-based recombinant protein production. It involves in vitro transcription and translation in a cell-free medium. In this work, we implemented CFPS in a plastic array device. Each unit in the array consisted of an inner well and an outer well. Two synthesis steps, gene transcription and protein translation, took place in the inner well, in which a cell-free medium was used to provide ribosomes and additional components necessary for protein synthesis. The outer well was concentric to the inner well and it functioned as a nutrient reservoir. A nanoporous membrane was sandwiched between the inner and outer wells for retaining the synthesized proteins and removing the reaction byproducts. A microfluidic channel was employed to connect these two wells for supplying fresh nutrients for longer reaction time and higher expression yield. Synthesis of luciferase was shown to last 8 times longer and yield 10 times more proteins than in a conventional container. The device also enables more than 2 orders of magnitude reduction in reagent consumption compared to a bench-top instrument. The effects of the membrane pore size and microfluidic channel on the protein production yield were also studied. The array device has potential to become a platform for parallel protein expression for proteomics applications, matching high-throughput gene discovery.