Large constructs of DNA of arbitrary sequences can be assembled with relative ease by joining short synthetic oligonucleotides, and the readiness of these synthetic genes will have significant impact on research in biology and other protein-related applications. Currently, high throughput gene synthesis is unlikely due to the limit of oligonucleotide synthesis.

We developed a microfluidic PicoArray method for simultaneous synthesis and purification of oligonucleotides designed for multiplex gene synthesis. Given the critical quality need of gene synthesis by ligation and/or polymerase chain reaction, we used a model of DNA synthesis to improve key reaction steps and the oligonucleotides obtained were successfully used in ligation under thermal cycling conditions to give DNA constructs of several hundreds of base pairs, and ligation in combination with fusion PCR is effective in assembling of multiple kbp DNA constructs. Protein expression using the genes thus synthesized is demonstrated. The method is further successfully applied to the codon optimization of the 21 genes from a 30S ribosomal subunit (George Church and co-workers, described in a separate report). These results illustrate the potential of microfluidics-based ultra-fast oligonucleotide parallel synthesis as an enabling tool for modern synthetic biology such as construction of genome-scale vectors and cell free proteome protein expression. It is exciting to foresee one day protein libraries can be made as easily as libraries of small molecules so that the functions encoded in protein sequences can be fully explored to benefit human health and life.