Liquid Crystalline Assembly of Collagen for Deterministic Alignment and Spread of Human Schwann Cells

TL;DR

This study demonstrates a novel method for aligning collagen at large scales and within 3D hydrogels at concentrations below traditional LC-forming levels, effectively guiding human Schwann cell growth.

Contribution

It introduces a new approach for collagen alignment using shear and magnetic fields at sub-LC concentrations, enabling biomimetic ECM fabrication.

Findings

Large-scale collagen alignment achieved below LC concentration thresholds.

Aligned collagen substrates direct Schwann cell spreading and morphology.

Magnetic field strength determines the extent of collagen alignment.

Abstract

Collagen is a key component of the extracellular matrix and well-oriented domains of collagen are relevant for mimicking the local cell environment in vitro. While there has been significant attention directed towards the alignment of collagen, formation of large-scale oriented domains remains a key challenge. Type I collagen self-assembles to form liquid crystalline (LC) mesophases in acidic conditions at concentrations above 100 mg/ml. The LC mesophase provides an efficient platform for large-scale alignment and patterning of collagen coated substrates. However, there exist challenges related to solubilizing and processing of collagen at such high concentrations in order to replicate the native extra cellular matrix (ECM). In this contribution, we report on centimeter-scale alignment in collagen-coated glass substrates using solutions that are well below the LC-forming concentrations. Importantly, we are also able to extend this method to create a mimic of the native ECM via macroscopic 3-D collagen hydrogels with programmed anisotropy within them. We explain the formation of these uniform domains via shear-induced and magnetically-induced liquid crystallinity of the collagen solutions. We show that the orientation, spreading and aspect ratio of Human Schwann Cells (HSCs) all are strongly coupled with the alignment of the collagen substrate/hydrogel. We use a simple Metroplis-based model to reveal that a critical magnetic field strength exists for a given concentration of collagen, exceeding which, macroscopic alignment is permissible- enabling guidance for future studies on alignment of collagen at high concentrations.