The generation of replacement organs and tissues relies on the design of components that replicate the three-dimensional (3D) structures and physiologies found in the body. The current knowledge basis is derived from biochemical analysis of disrupted tissues, in vitro preparations and clinical observations. While great strides have been made in developing new biomaterials, the tissue engineering efforts focused on nerve repair have been limited by a rudimentary understanding of how neurons interact with their 3D environment. For example, even the most successful implantable therapeutics for nerve repair, guidance channels, approach the performance of grafted tissue only in cases of minor nerve injuries. Our overall goal is to develop new 3D matrices that are specifically designed to a) mimic the properties of soft nervous tissues and b) enable new fundamental investigations of how scaffold physical properties (e.g., porosity and mechanical properties) impact neuronal response. Work to date investigating cell response has primarily varied scaffold physical properties by altering gel concentration. However, changing the gel density also affects the porosity of the scaffold, thus influencing the diffusion of nutrients, oxygen, growth factors, as well as, waste removal. For this reason, to completely understand the cells' response to scaffold mechanical properties independent of porosity, we must first design new tunable biomaterials. Hydrogels are often used as artificial matrices for cell growth due to their hydrophilicity. In order to successfully support directed cell and tissue growth, hydrogel scaffolds must meet a number of requirements. These include structural similarity to the extracellular matrix, biocompatibility, biodegradability, as well as, resistance to non-specific protein adsorption. One hydrogel of choice in poly(ethylene glycol) (PEG), because it fulfills most of the requirements imposed on the scaffold's design, and it is approved by FDA for biological use. However, PEG is not degradable and this function must be added by the incorporation of peptides or hydrolyzable groups incorporated in the backbone or during copolymerization. In this study we use PEG vinyl sulfone gels, polymerized with a PEG-dithiol cross-linker. One benefit of this hydrogel is that it can be polymerized in physiological conditions and thus can be seeded with cells prior to polymerization. Further, we explore the change in mechanical properties and porosity by utilizing PEG star polymers of varying arm length and number and by manipulating cross-linker density. Thus far, we have synthesized PEG hydrogels that span a range of mechanical properties (G', 0.4-5 kPa) that mimics human nervous tissue (e.g., brain and spinal cord). We will present current work with a focus on (a) characterization of gel porosity, (b) development of strategies for tuning gel stiffness independently of porosity, (c) addition of biological properties to the matrix by incorporating enzymatically degradable peptides as cross-linkers, (d) addition of common adhesive ligands to the scaffolds to promote neuronal outgrowth, and (e) investigation of neuronal response to these novel scaffolding biomaterials with varying tunable properties. This work will ultimately lead to a fundamental quantitative understanding of how to more effectively design tissue engineering scaffolds for directed neuronal response and may result in advanced model systems for in vitro neurobiology studies as well as improved materials to treat neural injuries and degradation.