A major challenge in tissue regeneration is to direct the assembly of cells and their extracellular matrix (ECM) into arrangements that possess the unique physical and mechanical properties of the native tissue. We have developed a unique template that directs alignment of confluent cells and ECM across an entire two-dimensional surface. The template is a reactive, two-component interface that is synthesized in three steps in nanometer thick, micron-scaled patterns on silicon and on several biomaterial polymers.
In this method, a volatile zirconium alkoxide complex is first deposited at reduced pressure onto a surface pattern that is prepared by photolithography; the substrate is then heated to thermolyze the organic ligands to form surface-bound zirconium oxide patterns. The thickness of this oxide layer ranges from 10 to 70 nanometers, which is controlled by alkoxide complex deposition time. The oxide layer is treated with 1,4-butanediphosphonic acid to give a patterned monolayer whose composition and spatial conformity to the photolithographic mask are determined spectroscopically.
NIH 3T3 fibroblasts and human bone marrow-derived mesenchymal stem cells attach and spread in alignment with the pattern and maintain alignment as they grow to form a confluent monolayer across the entire substrate surface. Confluent cells assemble an ECM, in which the fibronectin fibrils are highly aligned. Decellularization yields a composite material with spatially aligned matrix attached to a synthetic polymer surface. We illustrate biologic function by oriented neurite outgrowth along the aligned matrix fibrils. Our results support the goal of developing aligned matrices to serve as platforms for integrating directed cell behavior with synthetic devices. This combination of simple chemistry with autologous stem cells could be a powerful tool for generating a naturally assembled ECM for spatially predetermined tissue repair.