Surface Functionalization of Bioanalytical Applications : Virus-decorated Gold Microshells and Modified Synaptic Cell Adhesion Molecules

Abstract

Abstract Surface Functionalization for Bioanalytical Applications: Virus-decorated Gold Microshells and Modified Synaptic Cell Adhesion Molecules

Chang Su Jeon Department of Chemistry, Analytical Chemistry The Graduate School Seoul National University

Solid-phase extraction (SPE) is a sample preparation method used as a means of separation, concentration, and purification for analysis of complex unknown samples in the analytical field. Recently, there have been efforts to increase binding affinity, sensitivity, and selectivity through biomimetic surface engineering. In the analysis of complex biological samples, like blood and cells, physical and chemical interactions between the solid-phase surface and target species are crucial. These interactions can be divided into those in which the target analyte directly interacts with the solid surface and those in which the secreted substance is observed upon the introduction of target analyte, including cells, to the surface. This dissertation describes (i) bio-inspired surface modifications for enhanced analyte-solid surface interactions and (ii) the purification of synaptic cell adhesion proteins for induced artificial synapses and bioanalysis.

Part I. Analyte-solid surface interaction: virus-decorated magnetic gold microshells with biomimetic architectures for enhanced immunoassays

Filamentous phage virus has similar structural dimensions to many cellular threadlike structures that enhance the cellular functions. The aim of this study was to combine the virus and microshells to resemble biological systems, thereby harnessing the enhancement factors originating from the unique morphology. We implemented gold layer on a microshell to form a self-assembled monolayer that help with chemical modifications using streptavidin and protection from non-specific adsorptions. Phage virions that carry biotins within their tails were prepared for directional binding of the virions to streptavidin-modified gold microshells. We confirmed the augmented yield of antibody loading on virus-modified gold microshells because of the increased surface to volume ratio. Indeed, the sensitivity has increased up to nine-fold for the detection of cardiac marker proteins. This work demonstrates the feasibility of merging viruses with non-biological substrates to yield biomimetic tools for the enhanced analyte-decorated solid surface interactions.

Part II. Cell-solid surface interaction: purified synaptic cell adhesion molecules for induced artificial synapse

Conventional neural interfaces solely depend upon passive physical contact between nerve cells and their non-biological counterparts. Nerve cells in the brain, however, communicate via synapses of which spatiotemporal specificity is exquisitely regulated. Here, we report a newly engineered postsynaptic cell adhesion molecules (CAMs) that are fluorescent and biotinylated to facilitate its purification, quantification, tracking, and immobilization on inorganic substrates. The independence of synaptic CAMs on the lipid membranes, originating from the orientation-controlled immobilization, extends versatility of the protein to fit in artificial synapse formation between neurons and various types of inorganic solid substrates. Moreover, this method will be used as the basis for studying the interaction between the cell and solid surface.

Keywords: gold microshell, suspension array, non-specific binding, virus, artificial synapse, neuroligin, synaptic cell adhesion molecules Student number: 2009-22920