Investigation of approaches for the fabrication of protein patterns by scanning probe lithography

This paper investigates three different approaches to patterning proteins w ithin ultrathin resist layers formed from self-assembled monolayers using s canning probe lithography (SPL) at the submicrometer length scale. The firs t approach uses a "nanografting" method to pattern a reactive carboxylic ac id terminated thiol into a resist composed of a methyl-terminated monolayer . Rabbit IgG antigen is bound to the patterned region, and an immunoassay u tilizing direct readout of the topographic change resulting from specific b inding of anti-rabbit IgG antibody is performed using scanning force micros copy. To address issues related to nonspecific protein adsorption, the othe r two approaches investigated the patterned removal of glycol-terminated mo nolayers by mechanically "scraping" patterns at high tip-sample forces by S PL. Protein attachment to the scraped regions was achieved either through t he chemisorption of a disulfide coupling agent or by the direct adsorption of Fab'-SH antibody fragments. Results obtained from all approaches are pre sented and compared, and the strengths and weaknesses of each toward fabric ating high-density, multiple protein arrays are discussed.