AVS 47th International Symposium
    Biomaterial Interfaces Tuesday Sessions
       Session BI-TuM

Paper BI-TuM4
A Surface Plasmon Resonance Biosensor Study of Protein Interactions with Thin Apatite Films

Tuesday, October 3, 2000, 9:20 am, Room 202

Session: Protein-Surface Interactions
Presenter: H.B. Lu, University of Washington
Authors: H.B. Lu, University of Washington
B.J. Tarasevich, Battelle Pacific Northwest National Laboratory
C.T. Campbell, University of Washington
C. Giachelli, University of Washington
B.D. Ratner, University of Washington
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The primary objective of this research is to study protein interaction with a well-characterized apatite film using a surface plasmon resonance (SPR) sensor. Due to the remarkable osteointegration properties of apatite as an implant material, protein adsorption onto this type of material has been intensively studied. It is believed that knowledge on protein adsorption to such apatite surface will help us to understand the body's response to foreign materials and improve implant performances. However, due to the limitations of analytical tools for either material characterization or protein adsorption, few useful conclusions have been reached. In this study, a gold SPR sensor has been functionalized with a carboxylic acid-terminated self-assembled monolayer and then coated with an apatite thin film grown with the surface-induced mineralization technique. The apatite mineral films have been well characterized using surface analytical tools including TOF-SIMS, XPS, FTIR, and AFM, as well as bulk analytical technique XRD. SPR is an optical phenomenon that is very sensitive to refractive index changes perturbing the evanescent wave at metal-liquid interfaces. By coating the SPR sensor with a thin apatite film, we took advantages of continuous and label-free monitoring, and thus studied protein interactions with apatite in real time. The proteins studied include phosphorylated Rat His osteopontin (p-OPN), non-phosphorylated Rat His osteopontin (n-OPN), and bovine serum albumin (BSA). The p-OPN displayed very distinguishable adsorption/desorption behavior from that of n-OPN and BSA. The p-OPN has a higher affinity toward the apatite surface, compared to n-OPN and BSA. The p-OPN may have inhibited mineral growth upon adsorption, while BSA may have promoted slight mineral growth upon adsorption. On the other hand, these proteins behaved non-selectively when adsorbing onto control surfaces including bare gold, a COOH-terminated SAM and an NH2-terminated SAM.