Surface functionalization of thin-film diamond for highly stable and selective biological interfaces

Abstract

Carbon is an extremely versatile family of materials with a wide range of mechanical, optical, and mechanical properties, but many similarities in surface chemistry. As one of the most chemically stable materials known, carbon provides an outstanding platform for the development of highly tunable molecular and biomolecular interfaces. Photochemical grafting of alkenes has emerged as an attractive method for functionalizing surfaces of diamond, but many aspects of the surface chemistry and impact on biological recognition processes remain unexplored. Here we report investigations of the interaction of functionalized diamond surfaces with proteins and biological cells using X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and fluorescence methods. XPS data show that functionalization of diamond with short ethylene glycol oligomers reduces the nonspecific binding of fibrinogen below the detection limit of XPS, estimated as >97% reduction over H-terminated diamond. Measurements of different forms of diamond with different roughness are used to explore the influence of roughness on nonspecific binding onto H-terminated and ethylene glycol (EG)-terminated surfaces. Finally, we use XPS to characterize the chemical stability of Escherichia coli K12 antibodies on the surfaces of diamond and amine-functionalized glass. Our results show that antibody-modified diamond surfaces exhibit increased stability in XPS and that this is accompanied by retention of biological activity in cell-capture measurements. Our results demonstrate that surface chemistry on diamond and other carbonbased materials provides an excellent platform for biomolecular interfaces with high stability and high selectivity.biointerfaces | surface chemistry | cells

Theory, fabrication and applications of microfluidic and nanofluidic biosensors

“…Other self-assembly methods use molecular assembly of alkanethiols to form organized monolayers that enable surface modification [56], as discussed below. Other methods include pick-andplace approaches using advanced tools such as optical tweezers [124,125] and AFMs [41,103,126]. Most of these methods are highly specific and remain in research phases with only a few manufactured biosensors.…”

Surface chemistry: Key to control and advance myriad technologies

“…The article here by Stavis et al (46) highlights some recent developments in methods for imparting biological compatibility and bio-recognition to diamond and other carbon surfaces and measurements that determine the success of those efforts. Their results show that photochemical grafting of short ethylene glycol (EG) oligomers to diamond surfaces produces a layer whose EG unit density is comparable with that for EG-based self-assembled monolayers on gold, which substantially reduces the nonspecific binding of proteins (to less than 3% of a monolayer).…”

Modeling the Interface between Biological and SyntheticComponents in Hybrid Nanosystems

“…Glass or gold substrates are typically used for anchoring proteins such as antibodies, but the polyethylene glycol and lipid bilayer coatings commonly used to prevent protein adsorption to their surfaces break down within two days [60]. Ultrananocrystalline diamond (UNCD) is a novel substrate composed of 2-5 nm diameter, phase-pure diamond grains on which alkene functionalization layers show excellent stability [1]. To compare the performance of immunosurfaces made with UNCD substrates to those made with a typical glass slide, immunosurfaces were created by covalently attaching antibodies to either UNCD films functionalized with aminodecane or Corning GAPS II amine-terminated glass (GAPSG) slides.…”

“…Researchers can create surfaces patterned with 25 nm diamond grains [1,2], nanopores smaller than the width of duplex DNA [3], macroscopic-length channels with cross-sections smaller than ten nanometers [4], and hollow metal-oxide macromolecular spheres measuring 4 nm across [5]. Although manufacturing structures with feature sizes of several nanometers is now possible, how these structures will interact with biomolecules is difficult to predict.…”