(85b) Properties of the Cell-Biomaterial Interface That Influence Nonviral Gene Delivery

The interaction of cells with biomaterial surfaces is important for many biotechnological and therapeutic applications that incorporate nonviral gene delivery, including tissue engineering scaffolds where gene delivery can present chemical factors to guide tissue formation in regeneration matrices for treatment of organ loss and failure. Surface properties, including wettability and surface chemistry, influence cell-surface interactions either directly or through an adsorbed protein layer, which itself is influenced by the underlying characteristics of the surface. Many different types of proteins adsorb onto biomaterial surfaces immediately upon contact with physiological fluids, and cell adhesion to these proteins provides mechanical coupling to the underlying substrate and triggers signals that direct subsequent cellular responses. Many proteins of the extracellular matrix (ECM), including fibronectin (FN), play important roles in cell adhesion, migration, growth, and differentiation. FN also plays a role in adhesion of many cell types to artificial biomaterials. Upon adsorption to biomaterial surfaces, FN undergoes conformational changes that modulate the functional presentation of ligands that lead to differences in integrin receptor binding and associated cell adhesion, proliferation, and differentiation. In addition to mediating cell response to biomaterials through adsorption to the surface, the incorporation of FN to nonviral DNA delivery schemes has been shown to enhance transfection, presumably by enhancing association of DNA complexes with cells and potentially by enhancing internalization. Taken together, observations show that biomaterial surface chemistry and surface-induced conformational changes in adsorbed FN can affect cell behavior and these same proteins can separately affect nonviral gene delivery; the goal of this project is to investigate the ability of biomaterial surface properties to control nonviral gene delivery through surface chemistry and protein adsorption and subsequently correlated to cellular behaviors controlled by cell-biomaterial interactions. Self-assembled monolayers (SAMs) of alkanethiols on gold were used as model biomaterials to investigate the effect of surface properties on nonviral gene transfer to cells adhered to these surfaces. SAMs presenting terminal CH₃, OH, COO^-, and NH₃⁺ functionalities were adsorbed with either a monolayer or multilayer of FN, onto which cells were then seeded and plasmid DNA was delivered via a bolus approach using polymer- and lipid-mediated delivery techniques. SAMs without adsorbed FN were used as a comparison, in addition to traditional polystyrene (PS) culture surfaces. FN dose response and underlying surface properties together contributed to transfection profiles, which, for lipid-mediated delivery, exceeded levels on traditional PS surfaces, even with the addition of FN. These results indicate not simply the presence of FN, but also its interaction with the underlying surface and resulting cell behaviors, enhance transfection. After FN multilayer adsorption to SAMs, the CH₃-terminated surface had the greatest transfection in comparison to all other SAMs and the PS control. We propose this increase can be correlated to cytoskeleton reorganization and FN fibrillogenesis. These studies allow us to begin to understand the relationships between biomaterial surface properties, adsorbed proteins, and nonviral gene transfer to cells interacting with these surfaces in order to design optimal material surfaces that promote gene delivery for use in therapeutic and diagnostic applications.