AVS 52nd International Symposium
    Biomaterial Interfaces Wednesday Sessions
       Session BI1-WeM

Paper BI1-WeM2
Functionalization of Diamond and Silicon Surfaces with Molecular Monolayers to Control Protein-Surface Interactions

Wednesday, November 2, 2005, 8:40 am, Room 311

Session: Protein-Surface Interactions
Presenter: R.J. Hamers, University of Wisconsin-Madison
Authors: T. Lasseter Clare, University of Wisconsin-Madison
B. Clare, University of Wisconsin-Madison
N. Abbott, University of Wisconsin-Madison
B.M. Nichols, University of Wisconsin-Madison
R.J. Hamers, University of Wisconsin-Madison
Correspondent: Click to Email
We have investigated the chemical functionalization of diamond and silicon surfaces with short ethylene glycol (EG) oligomers to control the the nonspecific adsorption of proteins to these surfaces. EG oligomers bearing a terminal vinyl group were linked to H-terminated surfaces of diamond and silicon using illumination with ultraviolet light at 254 nm. The resulting layers were characterized by XPS, and the effects of EG oligomers on binding of avidin, casein, fibrinogen, and BSA were qualitatively investigated using on-chip fluorescence measurements. To avoid issues related to fluorescence quenching and facilitate quantitative comparison on different materials, we measured avidin adsorption using an elution method. These experiments show that EG-modified surfaces of nanocrysalline diamond, single-crystal silicon, and polycrystalline gold films all resist binding of avidin to nearly the same extent. One of the attractive features of diamond is its extraordinary chemical stability. In a comparison of EG-modified surfaces of diamond, silicon, and gold, we find that gold and silicon samples undergo a significant degradation over a time period of approximately 1 week, while EG-diamond samples undergo no detectable change. These results are corraborated with XPS measurements that show silicon and gold undergo partial loss of their functionalization layers, while EG-diamond shows no measurable change. The effects of surface roughness were investigated by comparing EG-modified surfaces of nanocrystalline, polished, and cleaved single-crystal diamond. The influence of monolayer termination and other factors will also be presented. Overall, these measurements show that photochemical modification of Si and diamond with vinyl-terminated EG oligomers is a very effective way to reduce nonspecific adsorption. They also provide new molecular insights into the factors the control protein adsorption at surfaces.