Covalently Modified Silicon and Diamond Surfaces:  Resistance to Nonspecific Protein Adsorption and Optimization for Biosensing

Abstract

We report the direct covalent functionalization of silicon and diamond surfaces with short ethylene glycol (EG) oligomers via photochemical reaction of the hydrogen-terminated surfaces with terminal vinyl groups of the oligomers, and the use of these monolayers to control protein binding at surfaces. Photochemical modification of Si(111) and polycrystalline diamond surfaces produces EG monolayers linked via Si-C bond formation (silicon) or C-C bond formation (diamond). X-ray photoelectron spectroscopy was used to characterize the monolayer composition. Measurements using fluorescently labeled proteins show that the EG-functionalized surfaces effectively resist nonspecific adsorption of proteins. Additionally, we demonstrate the use of mixed monolayers on silicon and diamond and apply these surfaces to control specific versus nonspecific binding to optimize a model protein sensing assay.

Nanoindentation as a Tool to Clarify the Mechanism Causing Variable Stiffness of a Silane Layer on Diamond

“…Diamond may be more biocompatible for direct protein immobilization than, for example, metal surfaces [22]. However, from our experience of single-molecule dynamics [23,24], as well as that of others' [10,[25][26][27][28][29][30], we still recommend the use of an intervening layer for preserving enzymatic activities. Polymer layers have a distinct advantage compared with flat solid surfaces in terms of retaining protein activity.…”

Modeling the Interface between Biological and SyntheticComponents in Hybrid Nanosystems

“…It is known that without a protective coating of aminopropylsilane on silica or aminodecane on diamond surfaces, the antibodies can bind nonspecifically to both surfaces [61,29], losing their conformation and specific affinity to antigens. However, it is not known how the antibody proteins could interact with the substrates in the presence of the functionalization layer and how the functionalization layer degrades in solution.…”

The interaction of organic adsorbate vibrations with substrate lattice waves in methyl-Si(111)-(1 × 1)

“…9,10 Si(111) surfaces can be terminated with methyl groups in a highly controlled manner, which results in coverage by a full monolayer 6 with essentially every Si atom on the surface bonded to a methyl group. Relative to the hydrogenterminated Si(111) surface, methyl-terminated Si(111) surfaces exhibit enhanced resistance to oxidation in air.…”