Cell‐Free Protein Synthesis in Microfluidic Array Devices

Abstract

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.

Miniaturized fluid array for high‐throughput protein expression

“…Continuous supply of nutrients was due primarily to the concentration gradient of each component between two chambers. 22 The same diffusion mechanism also facilitated the removal of small molecular byproducts of protein expression. The byproducts, such as pyrophosphate ions from hydrolysis of triphosphates, could inhibit protein synthesis if accumulated to a significant level.…”

“…As shown in Figure 1b, each unit is composed of (1) a reaction chamber containing DNA plasmid vectors and components required for gene transcription and protein translation, (2) a feeding chamber containing nutrients (e.g., amino acids and adenosine triphosphate), and (3) a microchannel to connect these two chambers and a dialysis membrane that separates them. The dimension of the microchannel can range from hundreds of microns to a few millimeters 22 ; the most of this work was performed at 4 mm. Both top and bottom layers were machined from polypropylene sheets (Plastruct).…”

“…4 Efforts have also been made in applying microfluidics to CFPS, [19][20][21] but they have not addressed the need for high-throughput parallel protein production. Our earlier efforts 22,23 have been limited to a six-well device producing three proteins. A large number of microfluidic channels have also been used for CFPS, 24 though lack of separation between nutrients and reactants preclude prolonged protein expression.…”

Cell-Free Protein Synthesis in Miniaturized Array Devices and Effects of Device Orientation

“…This trend is in general agreement with the hydrostatic pressure effects previously observed in the Horizontal Device. 19 The greatest protein expression occurs when the height difference between the feeding and reaction solutions is greater than 2 mm. At this height difference, hydrostatic pressure increases the influx of feeding solution into the reaction chamber, supplementing the reaction solution with a greater amount of nutrients and energy for protein expression.…”

“…However, this exchange of small molecules between the reaction solution and the feeding solution occurs passively through the membrane, and the protein synthesis yield is generally greater. [18][19][20] Recently, miniaturized CFPS in the continuous-exchange format have been studied in order to achieve high throughput, reduce reagent consumption, and speed up protein synthesis. These goals have been accomplished in the form of droplets, [21][22][23][24] protein-producing gel, 25 and microfluidic devices.…”