Photocatalytic Nanolithography of Self-Assembled Monolayers and Proteins

Self-assembled monolayers of alkylthiolates on gold and alkylsilanes on silicon dioxide have been patterned photocatalytically on sub-100 nm length-scales using both apertured near-field and apertureless methods. Apertured lithography was carried out by means of an argon ion laser (364 nm) coupled to cantilever-type near-field probes with a thin film of titania deposited over the aperture. Apertureless lithography was carried out with a helium–cadmium laser (325 nm) to excite titanium-coated, contact-mode atomic force microscope (AFM) probes. This latter approach is readily implementable on any commercial AFM system. Photodegradation occurred in both cases through the localized photocatalytic degradation of the monolayer. For alkanethiols, degradation of one thiol exposed the bare substrate, enabling refunctionalization of the bare gold by a second, contrasting thiol. For alkylsilanes, degradation of the adsorbate molecule provided a facile means for protein patterning. Lines were written in a protein-resistant film formed by the adsorption of oligo(ethylene glycol)-functionalized trichlorosilanes on glass, leading to the formation of sub-100 nm adhesive, aldehyde-functionalized regions. These were derivatized with aminobutylnitrilotriacetic acid, and complexed with Ni2+, enabling the binding of histidine-labeled green fluorescent protein, which yielded bright fluorescence from 70-nm-wide lines that could be imaged clearly in a confocal microscope

Fabrication of nanometer-sized protein patterns using atomic force microscopy and selective immobilization.

A new methodology is introduced to produce nanometer-sized protein patterns. The approach includes two main steps, nanopatterning of self-assembled monolayers using atomic force microscopy (AFM)-based nanolithography and subsequent selective immobilization of proteins on the patterned monolayers. The resulting templates and protein patterns are characterized in situ using AFM. Compared with conventional protein fabrication methods, this approach is able to produce smaller patterns with higher spatial precision. In addition, fabrication and characterization are completed in near physiological conditions. The adsorption configuration and bioreactivity of the proteins within the nanopatterns are also studied in situ