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

Cell-free protein synthesis (CFPS) has been used as an alternative to cell-based recombinant technology for protein production in academic and industrial labs. The continuous-exchange format generally has higher expression yield by constantly supplying a nutrient solution and removing inhibitory by-products through a porous membrane. Because of the concern of possible membrane clogging by large molecules in the CFPS solution, we investigated the effects of membrane orientation on protein synthesis. We fabricated a miniaturized array device called Vertical-I with its membrane oriented vertically in reference to the table surface and found that the protein synthesis yield in the Vertical-I device was 144% higher than the Horizontal Device reported previously. The reaction time was also faster; β-glucuronidase reached the synthesis yield plateau after 2 h in the Vertical-I device versus 4 h in the Horizontal Device. Possible clogging of membrane pores was confirmed by fluorescein diffusion measurement. Using these results, we designed a device called Vertical-II that would fit into a 96 well plate holder for compatibility with commercial reagent dispensers and microplate readers. The experimentally optimized device increased protein expression 406% over the Horizontal Device and consumes 5 times fewer reagents than a commercial device, showing the potential for high-throughput protein synthesis.