Protein Adhesion on SAM Coated Semiconductor Wafers: Hydrophobic versus Hydrophilic Surfaces

Abstract

The interface of biology and semiconductor materials has become an important topic of interest as researchers are merging living organisms with microelectromechanical systems (MEMS) in the pursuit of new microfabricated biomedical devices. Biological cells interface with the semiconductor surface through a host of interactions that are mediated by protein adhesion and film formation. To better understand this interface, we have conducted protein adsorption studies of a model system using bovine serum albumin (BSA) and compared it to the adsorption from a complex protein mixture of cell growth serum on uncoated and self-assembled monolayer (SAM) coated silicon wafers. Several characterization techniques -AFM, ellipsometry, water contact angle, and fluorescence microscopy -were used to evaluate the protein-adsorbed layer. An uncoated silicon surface was most attractive to proteins, forming a 70 Å thick film from a solution of BSA at a concentration comparable to that in cell growth serum. Coating with the hydrophobic octadecyltrimethoxysilane (OTMS) SAM reduced protein adhesion by ~15%. In contrast, a hydrophilic N-(triethoxysilylpropyl)-O-polyethyleneoxide urethane (TESP) SAM inhibited protein adhesion by greater than 50%. Protein adhesion studies with cell growth sera containing complex mixtures of proteins paralleled the BSA adsorption studies, clearly identifying the TESP coated surface as a promising biocompatible coating.4

Poly(dimethylsiloxane) thin films as biocompatible coatings for microfluidic devices: Cell culture and flow studies with glial cells

“…The surfaces mentioned above were treated by soaking them in protein containing PBS solution for 2 h at room temperature. The exposure time was deliberately set at a point beyond the saturation of binding, as determined by previous studies, 35 to ensure maximal protein coverage. Typically, saturation of binding occurs within the first several minutes.…”

Investigation of the ability of a silica “seed” layer to improve the thermal and aqueous immersion stability of alkylsilane monolayers on silicon oxide surfaces

“…For methoxysilanes, a method reported by Follstaedt et al is employed with slight modification [13]. Briefly, 0.85 mL of the precursor is added to 40 mL of Optima grade hexanes in a glass beaker and mixed gently by pipetting the solution in and out of a Pasteur pipette.…”

“…Surface modification by organosilane precursors has been shown to alleviate non-specific protein adsorption on surfaces [12][13][14][15] and in micro-channels [16][17][18]1], to affect electroosmotic flow [19], and to alleviate cell adhesion in microchannels [18,1]. In light of these considerations, surface modification by organosilane precursors is potentially an enabling technology for the commercialization of bio-MEMS and microfluidic devices.…”

“…The thickness of films formed from vinyltrichlorosilane is reduced by almost 38% in physiological conditions [2], and the poor immersion stability of alkylsilane monolayers on titanium dioxide and zirconium dioxide has also been reported [20]. Polyethylene glycol [15,14] and polyethylene oxide [21,13,18], which are materials well-known to reduce non-specific protein adsorption, have been deposited via organosilane chemistry and have been proven to inhibit non-specific protein adsorption. However, it has also been reported that the stability of these films is compromised in aqueous environments [14].…”

Protein adsorption resistance of anti-biofouling block copolymers containing amphiphilic side chains

“…[12][13][14] In marked contrast, however, hydrophobic surfaces have demonstrated a tendency to adsorb proteins at elevated levels. 15,16 Thus, the protein adsorption behavior of an amphiphilic material capable of presenting both hydrophobic and hydrophilic moieties is of great interest, especially given many recent reported studies of amphiphilic surfaces. [17][18][19] Atomic force microscopy (AFM) 20 with chemically modified tips is a dynamic analytical technique that can be used to determine adhesion forces between the functionalities on the tips and surfaces of interest.…”