In-situ characterization of self-assembled monolayers of water-soluble oligo(ethylene oxide) compounds.
In-situ spectroscopic ellipsometry (SE) was utilized to examine the formation of the self-assembled monolayers (SAMs) of the water-soluble oligo(ethylene oxide) [OEO] disulfide [S(CH(2)CH(2)O)(6)CH(3)](2) {[S(EO)(6)](2)} and two analogous thiols - HS(CH(2)CH(2)O)(6)CH(3) {(EO)(6)} and HS(CH(2))(3)O(CH(2)CH(2)O)(5)CH(3) {C(3)(EO)(5)} - on Au from aqueous solutions. Kinetic data for all compounds follow simple Langmuirian models with the disulfide reaching a self-limiting final state (d=1.2nm) more rapidly than the full coverage final states of the thiol analogs (d=2.0nm). The in-situ ellipsometric thicknesses of all compounds were found to be nearly identical to earlier ex-situ ellipsometric measurements suggesting similar surface coverages and structural models in air and under water. Exposure to bovine serum albumin (BSA) shows the self-limiting (d=1.2nm) [S(EO)(6)](2) SAMs to be the most highly protein resistant surfaces relative to bare Au and completely-formed SAMs of the two analogous thiols and octadecanethiol (ODT). When challenged with up to near physiological levels of BSA (2.5mg/mL), protein adsorption on the final state [S(EO)(6)](2) SAM was only 3% of that which adsorbed to the bare Au and ODT SAMs.
Surface and Microanalysis Science Division, National Institute of Standard and Technology (NIST), Gaithersburg, MD 20899, USA.
Marlon L
ML
Walker
David J
DJ
Vanderah
Kenneth A
KA
Rubinson
D000327:Adsorption; D000818:Animals; D002417:Cattle; D004220:Disulfides / Q000737:chemistry; D005027:Ethylene Oxide / Q000737:chemistry*; D007700:Kinetics; D008422:Materials Testing; D008956:Models, Chemical; D011506:Proteins / Q000737:chemistry; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors; D014867:Water / Q000737:chemistry*
D004220:Disulfides; D011506:Proteins; D013438:Sulfhydryl Compounds; D014867:Water; D012710:Serum Albumin, Bovine; D005027:Ethylene Oxide