Plasma polymerization for protein patterning: Reversible formation with fullerene modification

Partial plasma polymerization for coexistence of hydrophobic/ hydrophilic area in several ten micrometer size is the typical technique for protein patterning. A hydrophobic hexamethyldisiloxane plasma-polymerized film (HMDS PPF) was deposited on a glass substrate and this surface was partially modified by subsequent nitrogen plasma treatment (hydrophilic surface, HMDS-N PPF) with a patterned shadow mask. An antibody protein (F(ab')₂ fragment of anti-human immunoglobulin G) was selectively adsorbed onto the HMDS-N area and was not adsorbed onto the HMDS area. Distinct 80×80 μm² square spots surrounded by a non-protein adsorbed 80 μm-wide grid were observed. Then, when the protein modified by fullerene was used, the reversible patterning was obtained. This indicated that the modification by fullerene changed the hydrophilic nature of F(ab')₂ protein to hydrophobic one, as a result, the modified protein was selectively adsorbed onto hydrophobic area.