The overall goal in our work is to develop new methods and materials for the fabrication of hierarchically structured, three-dimensional tissue engineering scaffolds. Conventional polymer scaffold production methods produce structures which commonly lack substantial strength, and there is difficulty in controlling porosity, pore distribution, and pore interconnectivity. Additionally, the chemical nature of these scaffolds is typically homogenous; as there is no mechanism for creating additional chemical functionality, distinct from the bulk chemistry, in a specified geometry on the scaffold. The ability to chemically modify selected regions inside the scaffold is one way to direct cell growth in deliberate patterns; which is necessary for the engineering of complex, functioning tissues. The aim of this work is to address these issues through the application of microstereolithography (microSL) to the fabrication of hierarchically structured tissue engineering scaffolds.

The use of photopolymerizable materials that can be selectively chemically modified during the SL part building process is one way to provide hierarchical structure to biomaterials. On one level, SL will allow for the building of complex 3D structures via its localized photopolymerization mechanism, with extremely well defined overall shapes and interconnected pore features. The second level of local chemical structure in the scaffold structure in our work is created by a modification of chemical groups inside the polymer scaffold as it is being fabricated by using a light induced deprotection reaction event. The specific systems under investigation utilize an acid catalyzed deprotection event to change the surface chemistry inside the SL-made polymer part from the normally hydrophobic surface to a more hydrophillic one, and is analogous to conventional chemically amplified photoresists. This chemical modification alters the surface energy, affecting how proteins interact with the material. This allows selective areas inside the scaffold to be more favorable towards cell adhesion, and a patterned cell culture can be grown on the 3D scaffold.

This presentation provides an update of the work including cell growth studies on the engineered materials, and the assembly of a custom built SL apparatus with the capability of exposure using two different wavelengths of light. Potential resin compositions are prepared and evaluated for biocompatibility, degradation rate, and capability for use in the SL apparatus.