Selective patterning and manipulation of gold colloids

We present a combination of micro/nanopatterning of DNA-tagged gold colloids and a method that allows for selective manipulation of gold colloids. The gold colloids can be selectively hybridized to surfaces pre-patterned with single-stranded DNAs. Micro-and nanopatterns were created using standard photolithography or X-ray interference lithography and converted into biologically meaningful patterns by molecular assembly pattering by lift-off technique. Well defined areas (i.e. spots) of biotinylated poly(L-lysine)-grafted-poly(ethylene glycol) (PLL-g-PEG/PEGbiotin) surrounded by a resistant surface of non-functionalized PLL-g-PEG were created. The biotin-avidin linkage was used to surface-immobilize single-stranded DNAs which offered the anchoring points for the cDNA-tagged gold colloids. In addition laser light was used to modify the surface immobilized single-stranded DNAs. This manipulation has a direct impact on the amount of hybridized DNA-tagged gold colloids. This fact allows us to create patches with defined gold colloid density and gradients on the surface as well as gradients. The combination of the patterning and the in situ manipulation approaches will find manifold applications in the field of biosensing and nanotechnology.