"To our knowledge, this is the first time MIMIC has been used for the patterning and self-assembly of 2D surface-layer protein arrays," Erika Györvary of the Universität für Bodenkultur Wien told nanotechweb.org. "MIMIC is a low-cost method that requires only a small amount of material and it is also a one-step technique, enabling rapid prototyping."

To carry out the technique, the scientists created grooved moulds from poly(dimethylsiloxane) (PDMS). They positioned the moulds face down on silicon wafers, forming microchannels between the surface of the wafer and the mould. Then they placed a solution of bacterial surface-layer (S-layer) proteins at the entrance to the microchannels: the solution filled the channels by capillary action. Finally, removing the mould after the S-layer proteins had had time to crystallize left a patterned array behind.

In this way, the scientists patterned the protein into sets of parallel tracks with track widths of roughly 820 nm and 6, 8 and 10 µm, as well as making a pattern using a set of meandering microchannels. The protein layer was 15 nm thick.

What's more, the patterning process did not affect the proteins' chemical functionality. The researchers proved this by attaching human IgG antibodies to the patterned protein molecules, binding antihuman IgG antigens labelled with fluoresceinisothiocyanate to the antibodies and imaging the results by epi-fluorescence microscopy.

"Future work will focus on the use of these patterned crystalline S-layer substrates in diagnostics and also for hierarchical self-assembly of nanocrystal-based nanoelectronic devices," added Györvary.