Functional Surface-immobilization of Genes Using Multistep Strand Displacement Lithography.

Immobilization of genes on lithographically structured surfaces allows the study of compartmentalized gene expression processes in an open microfluidic bioreactor system. In contrast to other approaches towards artificial cellular systems, such a setup allows for a continuous supply with gene expression reagents and simultaneous draining of waste products. This facilitates the implementation of cell-free gene expression processes over extended periods of time, which is important for the realization of dynamic gene regulatory feedback systems. Here we provide a detailed protocol for the fabrication of genetic biochips using a simple-to-use lithographic technique based on DNA strand displacement reactions, which exclusively uses commercially available components. We also provide a protocol on the integration of compartmentalized genes with a polydimethylsiloxane (PDMS)-based microfluidic system. Furthermore, we show that the system is compatible with total internal reflection fluorescence (TIRF) microscopy, which can be used for the direct observation of molecular interactions between DNA and molecules contained in the expression mix.