Assembly and Characterization of a Muscimol–Immobilized Silicon Surface

Abstract

Abstract: : Purpose: Efficient GABAergic neurotransmission is required for normal visual function in the retina. A severe consequence of certain retinal degenerative diseases is impaired neurotransmitter–mediated signaling from the photoreceptors to post–photoreceptor retinal neurons. An innovative approach to improve retinal function is the use of micro– or nanoscale devices to interact immobilized neurotransmitters or other active ligands with post–synaptic membrane receptors. As an expansion of initial work with GABA–analog surfaces (1), we have developed an immobilization strategy for muscimol, a potent GABA receptor agonist. Characterization data presented here show the results of surface modification steps and indicate successful muscimol immobilization on silicon wafers. Methods: Silicon surfaces were cleaned and hydroxylated before vapor–phase silanization in vacuum. The silanized surfaces were then incubated in a solution of avidin, EDAC and NHSS for avidin conjugation. Biotinylated muscimol was bound to the avidin–conjugated surfaces through avidin–biotin chemistry. Surfaces were analyzed with contact angle measurements and ellipsometry after each assembly step. Final surfaces were analyzed by X–ray photoelectron spectroscopy (XPS). Results: Ellipsometer data indicated height changes after each surface modification. Silanization, avidin conjugation and biotinylated muscimol immobilization increased surface heights by 20.5 +/– 3.47 Å, 14.2 +/– 2.09 Å and 12.3 +/– 2.51 Å, respectively. Contact angle measurements supported ellipsometry observations. The contact angles for the silanized, avidin–conjugated and biotinylated muscimol–immobilized surfaces were respectively 65 +/– 5.7°, 41.2 +/– 3.03° and 40.6 +/– 1.15°. XPS data further indicated successful muscimol immobilization by a C:N mass ratio increase compared to avidin–conjugated surfaces. Conclusions: The results indicate that the employed immobilization strategy based on avidin–biotin chemistry is effective for attaching muscimol to silicon surfaces. The data have inspired additional work to investigate the application of this technique to nanoscale surfaces and to integrate other neurotransmitter receptor effectors. (1) Vu et al., 2003 ARVO.

Keywords: neurotransmitters/neurotransmitter systems • synapse • retina