| A damaged central nervous system (CNS) has only a limited ability for repair and regeneration due to glial scarring, which acts as a physical and chemical barrier. A promising biomedical approach is to implant a biomaterial-based bridge into the CNS injury site to coax the damaged axons to penetrate through the glial scar and reestablish their synaptic connections. Biomaterials bearing extracellular matrix (ECM) proteins can provide the favorable growth environment required for successful neuronal cell adhesion and outgrowth. This dissertation aims to investigate the effects of neuronal outgrowth on biomaterial-based substrates with varying ECM protein coverages and patterns. Protein-modified substrates were prepared by micro-contact printing (muCP) techniques in concert with reactive surface chemistry. Test substrates and were carefully characterized by surface-sensitive analytical techniques.;The production, characterization, and use of a novel gradient substrate with varying concentrations of the ECM proteins fibronectin (FN) and laminin (LN) served as a platform to test neurite outgrowth. Gradient substrates were prepared by the controlled robotic immersion of cross-linker-modified substrates into a protein solution based on quantitative reaction immobilization isotherms for both proteins. X-ray photoelectron spectroscopy (XPS), Time-of-flight secondary ion mass spectrometry (ToF-SIMS), and contact angle goniometry were used to characterize and quantify the covalent chemical modification procedure, relative surface coverages, and overall quality. Dissociated sensory neurons from rat were used to test for cellular attachment and neurite outgrowth as a function of the local surface FN and LN concentrations.;Cellular preference for ECM proteins can be assayed on spatially patterned surfaces presenting two or more ECM proteins. Two-component FN-and LN-patterned substrates were fabricated and characterized by XPS, TOF-SIMS, epifluorescence microscopy, and atomic force microscopy (AFM). Prior to this work, the sequence of protein deposition of multi-protein patterned surfaces had not been investigated with respect to the resulting biological activity, spatial contrast, and surface coverage of each protein. Biological activity was measured using a fluorescence-based ELISA assay. The order of protein deposition significantly affected the relative biological activity of the uppermost and underlying immobilized proteins. As a result of these optimization studies, preferred substrate pattering methods produced well defined lanes of FN and LN with good spatial resolution, excellent "protein contrast", and good long-term interfacial stability. |
