Production of Highly Aligned Collagen Scaffolds by Freeze-drying of Self-assembled, Fibrillar Collagen Gels

Matrix and cellular alignment are critical factors in the native function of many tissues, including muscle, nerve, and ligaments. Collagen is frequently a component of these aligned tissues, and collagen biomaterials are widely used in tissue engineering applications. However, the generation of aligned collagen scaffolds that maintain the native architecture of collagen fibrils has not been straightforward, with many methods requiring specialized equipment or technical procedures, extensive incubation times, or denaturing of the collagen. Herein, we present a simple, rapid method for fabrication of highly aligned collagen scaffolds. Collagen was assembled to form a fibrillar hydrogel in a cylindrical conduit with high aspect ratio and then frozen and lyophilized. The resulting collagen scaffolds demonstrated highly aligned topographical features along the scaffold surface. This presence of an initial fibrillar network and the high-aspect ratio vessel were both required to generate alignment. The diameter of fabricated scaffolds was found to vary significantly with both the collagen concentration of the hydrogel suspension and the diameter of conduits used for fabrication. Additionally, the size of individual aligned topographical features was significantly dependent on the conduit diameter and the freezing temperature. When cultured on aligned collagen scaffolds, both rat dermal fibroblasts and axons emerging from chick dorsal root ganglia explants demonstrated elongated, aligned morphology and growth on the aligned topographical features. Overall, this method presents a simple means for generating aligned collagen scaffolds that can be applied to a wide variety of tissue types, particularly those where such alignment is critical to native function.