Novel Methods for Patterning Flat and Curved Soft Polymer Surfaces to Direct Cell Growth for Nerve Repair

Abstract

Tubular guide implants currently used to induce healing of peripheral nerve injury do not optimally mimic the environment of a naturally regenerating axon. The work described herein provides a method of templating cell alignment on biocompatible polymers that match the mechanical properties of nerve tissue. Aligned cells can assemble an aligned extracellular matrix, which can serve to improve structural and chemical cues for axonal regeneration. Methods were developed to chemically pattern two polymers with a cell-adhesive layer of zirconium oxide which is bound to a self-assembled monolayer of phosphonates. Patterning was characterized by x-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy, and atomic force microscopy. The first polymer, shape memory polymer, was patterned using photolithography and chemical vapor deposition. The second polymer, polycaprolactone fumarate (PCLF), is incompatible with photolithography; a stencil “shadow masking” method was instead developed to enable chemical patterning on flat surfaces. This method was then adapted to enable patterning of curved surfaces and the inside surfaces of tubes, which is unprecedented. Cells plated on and, where applicable, inside each of these surfaces were shown to align with the pattern, as was the extracellular matrix that they assembled. PC-12 cells, a cellular analog of neurons, were shown to extend neurites along the pattern on flat PCLF surfaces. Due to the success of this patterning method, an animal test has been scheduled to examine the capability of a patterned PCLF tube with an aligned ECM scaffold to induce regeneration of nerves in vivo.