(0001) 4H-SiC was functionalized with 3-aminopropyltriethoxysilane (APTES) and subsequently biotinylated for the immobilization of streptavidin. Atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), ellipsometry, fluorescence microscopy, and contact angle measurements were utilized to determine the structure, thickness, wettability, and reactivity of the resulting surfaces after each functionalization step. Initially, silicon carbide surfaces were exposed to an APTES solution for 5 min, 1 hr, and 16 hrs. It was determined that 1 hr and 16 hr exposure result in a multilayer APTES film on the SiC surface, whereas a 5 min exposure yields a near monolayer of APTES that is optimum for the subsequent biotinylation and streptavidin immobilization steps. A covalently bound layer of biotin was deposited on the 5 min APTES-functionalized SiC samples followed by successful conjugation of streptavidin. It was also shown that there was significant non-specific (electrostatic) binding of streptavidin to APTES functionalized SiC, thus revealing the importance of a uniform biotinylation step prior to streptavidin attachment. It was also proven that the biotinylated SiC surface is selective for only the streptavidin protein. The experimental results demonstrate that the APTES-functionalized and biotinylated SiC surfaces have the potential to be employed as a biosensing platform for the selective detection of streptavidin molecules.
Pub Type: Journals
4H-SiC, APTES, biotin, streptavidin, bioconjugation, surface functionalization, semiconductor biosensor