Functional PEG-Modified Thin Films for Biological Detection

Abstract

We report a general procedure to prepare functional organic thin films for biological assays on oxide surfaces. Silica surfaces were functionalized by self-assembly of an amine-terminated silane film using both vapor- and solution-phase deposition of 3'-aminopropylmethyldiethoxysilane (APMDES). We found that vapor-phase deposition of APMDES under reduced pressure produced the highest quality monolayer films with uniform surface coverage, as determined by atomic force microscopy (AFM), ellipsometry, and contact angle measurements. The amine-terminated films were chemically modified with a mixture of carboxylic acid-terminated poly(ethylene glycol) (PEG) chains of varying functionality. A fraction of the PEG chains (0.1-10 mol %) terminated in biotin, which produced a surface with an affinity toward streptavidin. When used in pseudo-sandwich assays on waveguide platforms for the detection of Bacillus anthracis protective antigen (PA), these functional PEG surfaces significantly reduced nonspecific binding to the waveguide surface while allowing for highly specific binding. Detection of PA was used to validate these films for sensing applications in both buffer and complex media. Ultimately, these results represent a step toward the realization of a robust, reusable, and autonomous biosensor.

Fundamentals of Biomedical Applications of Biomorphic SiC

“…The development of methods to tune the surface properties of two robust high bandgap materials, silicon-rich silicon nitride (SixN4, 3.5 < x < 4.5) and SiC would significantly increase the possible use of these materials. SixN 4 is widely used, for example, as waveguide material in refractometric (McDonagh et al, 2008) or fluorescence (Anderson et al, 2008) detection, and as coating material for sensors based on electrical impedance (Tlili et al, 2005) or vibrating microcantilevers (Goeders et al, 2008) SiC has a high potential for similar applications (Yakimova et al, 2007). For such sensing and biomedical applications, both materials would benefit from specific surface modification.…”

Direct Visualization of Single-Molecule DNA-Binding Proteins Along DNA to Understand DNA-Protein Interactions

“…This study also concluded that PEG-modified surfaces retain their protein and cell repulsive nature for the period of investigation, i.e., 28 days (Sharma et al, 2004). With regard to PEG stability in the air, no degradation was reported after 75 days (Anderson et al, 2008). In contrast to these macroscopic experimental studies, PEG-coated surfaces used for singlemolecule imaging imposes several challenges.…”

Silicon and Silicon-Related Surfaces for Biosensor Applications

“…Miniaturized microfluidics sensors, for example, can use silicon oxide or silicon nitride as waveguide and immobilization platform. In particular, Si x N 4 is widely used, for example, as waveguide material in refractometric [Karymov, et al, 1995] or fluorescence [Anderson, et al, 2008] detection. Among all optical techniques, one type of surface-based detection technique, surface plasmon resonance (SPR), has had magnificent success in the last 20 years [Phillips, K.S.…”