| Self-assembled monolayers (SAMs) are often used to control surface chemistry and to prepare substrates for biological study. Thiols on gold are the most widely used SAM system, but these substrates are only stable for 5-7 days under cell growth conditions. Silanes are an alternative to the thiol/gold system, which can be used on glass, a widely available and inexpensive surface material. Trimethoxysilanes are ideal monomers for silyl SAMs because of their compatibility with many functional groups, including esters and amides, their ease of purification by chromatography and their relatively high stability in typical ambient laboratory conditions. To determine the utility of siloxane for surface modification, the parameters for consistently forming dense, ordered SAMs from trimethoxysilanes were investigated.;Greater alkyl chain lengths are known to increase SAM order and stability. To increase order in SAMs formed from trimethoxysilanes, monomers with alkyl terminations of various lengths were synthesized. When monomer chain lengths were 16 carbons or greater, the SAMs produced were dense, ordered, and well-packed as characterized by transmission infrared spectroscopy. Further insight was gained into the mechanism of silyl SAM formation by comparing monomers of the same length (C20) but with different headgroups (triisopropoxysilane vs. trimethoxysilane). After annealing, holes were left in the monolayer proportional to the size of the headgroup, elucidating a nucleation plus growth mechanism for SAM formation.;SAM stability was monitored through protein adsorption studies. Hydrophobie patterns were microcontact printed onto glass with elastomeric stamps and backfilled using glycol-terminated trimethoxysilanes with 15 and 22 carbon alkyl chains. Patterned substrates were exposed to solutions of fluorescently labeled protein under cell growth conditions and at several time points the fluorescence was observed. Substrates were less prone to non-specific protein adsorption with the C22 glycol-terminated monomer than with the C15 glycol-terminated monomer. Further, patterns persisted longer for SAMs of the longer monomer. |
