AVS 49th International Symposium
    Applied Surface Science Friday Sessions
       Session AS+MM+BI-FrM

Paper AS+MM+BI-FrM3
Probing the Orientation of Surface-Immobilized IgG by ToF-SIMS

Friday, November 8, 2002, 9:00 am, Room C-106

Session: BioMEMS and Medical Devices
Presenter: H. Wang, University of Washington
Authors: H. Wang, University of Washington
D.G. Castner, University of Washington
B.D. Ratner, University of Washington
S. Jiang, University of Washington
Correspondent: Click to Email
The orientation of a surface-immobilized IgG is crucial for its ability to detect antigen in biosensors. To probe the orientation of a surface-immobilized IgG, two factors are important. One is a powerful surface analysis technique while the other is a well-controlled surface for specific protein orientation. Static time-of-flight secondary ion mass spectrometry (ToF-SIMS) is well suited for this purpose since the sampling depth of ToF-SIMS (1-1.5 nm) is less than the typical dimension of most proteins (4-10 nm). At the same time, IgG orientation can be controlled by appropriately adjusting microenvironments (e.g., surface charges and solution properties). In this work, we apply ToF-SIMS combined with principle components analysis (PCA) to study the orientation of anti-hCG (human chorionic gonadotropin) on two controlled surfaces using its Fab and Fc fragments as references. The controlled surfaces are achieved using self-assembled monolayers (SAMs) with different terminal groups. Results show that the combined ToF-SIMS and PCA technique is able to probe the difference in orientations for ani-hCG adsorbed on different surfaces. In addition, ToF-SIMS results are compared with those from the protein structure. Consistency of these results indicates the reliability of this method.