AVS 53rd International Symposium
    Biomaterial Interfaces Wednesday Sessions
       Session BI-WeM

Paper BI-WeM6
Biofunctionalizing Nitride Surfaces without Silanes

Wednesday, November 15, 2006, 9:40 am, Room 2014

Session: Bio-interfacial Modification and Bio-Immobilization I (Honoring Marcus Textor, ETH-Zürich for Substantial Contributions to the Field)
Presenter: R. Stine, Naval Research Laboratory
Authors: R. Stine, Naval Research Laboratory
K.M. McCoy, Naval Research Laboratory
S.P. Mulvaney, Naval Research Laboratory
L.J. Whitman, Naval Research Laboratory
Correspondent: Click to Email
Silicon nitride is widely used as a coating in the microelectronics industry because of its ability to resist penetration by contaminants such as water, oxygen, and ionic species. This property also makes silicon nitride a common terminal passivation layer for chip-based biosensors and bioMEMS devices, all of which come into contact with aqueous saline solutions. Current methods for biofunctionalizing silicon nitride rely almost exclusively on silane-based films, both for direct functionalization and as bifunctional linkers. However, even under stringent controls, the chemistry of silane films on silicon nitride surfaces is notoriously inconsistent and suffers from degradation over time when used in aqueous environments. We have developed an alternate, silane-free, method for functionalizing silicon nitride surfaces. The native oxide is first stripped via HF solution, and then treated with a plasma that makes the surface reactive to aldehydes. Using a bifunctional aldehyde coupler, we then adsorb a robust NeutrAvidin layer that can be used to immobilize any biotinylated biomolecule and has excellent nonfouling properties. We will describe the surface chemistry and compare our approach with silane-based methods as analyzed by XPS using fluorinated benzaldehyde. We will also show that this chemistry can be successfully applied to GaN surfaces, and used for both immunoassays and DNA hybridization assays in a range of sample matrices.