Bioengineering of silicon nitride

Selective functionalization of silicon nitride with biomolecules by light-dependent processes has been investigated. Aryldiazirin-based photoimmobilization procedures are used to achieve covalent biomolecule binding. Experimentally facile processes applied include the following steps: (i) adsorptive coating of the surface with photolabel-bearing reagents or photolabel-functionalized biomolecules; (ii) exposure of the coated surface to activating light (350 nm); and (iii) removal of excess reagent or functionalized biomolecule. The extent of photoreagent binding to silicon nitride depends on the time of light exposure as well as on the amount of photoreagent applied to the surface. Streptavidin is immobilized by photolinker polymer-mediated procedures, and antibody-derived F(ab') fragments are covalently immobilized on silicon nitride (45-50 fmol mm(-2)) with a low-molecular-weight crosslinker. Biomolecule binding is monitored by fluorescein-labelled ligand binding and by tracing radiolabelled proteins, respectively. Photoimmobilized streptavidin retains ligand binding activity, and immunoreagents remain biologically active. Mask-assisted photopatterning on silicon nitride is achieved and patterned structures are resolved by atomic force microscopic imaging of photobonded diazirin-derivatized bovine serum albumin.