Liquid Crystal Elastomers-A Path to Biocompatible and Biodegradable 3D-LCE Scaffolds for Tissue Regeneration

Abstract

The development of appropriate materials that can make breakthroughs in tissue engineering has long been pursued by the scientific community. Several types of material have been long tested and re-designed for this purpose. At the same time, liquid crystals (LCs) have captivated the scientific community since their discovery in 1888 and soon after were thought to be, in combination with polymers, artificial muscles. Within the past decade liquid crystal elastomers (LCE) have been attracting increasing interest for their use as smart advanced materials for biological applications. Here, we examine how LCEs can potentially be used as dynamic substrates for culturing cells, moving away from the classical two-dimensional cell-culture nature. We also briefly discuss the integration of a few technologies for the preparation of more sophisticated LCE-composite scaffolds for more dynamic biomaterials. The anisotropic properties of LCEs can be used not only to promote cell attachment and the proliferation of cells, but also to promote cell alignment under LCE-stimulated deformation. 3D LCEs are ideal materials for new insights to simulate and study the development of tissues and the complex interplay between cells.

Keywords: 3D scaffold; biocompatible; biodegradable; biomechanics; cell alignment; cell directionality; cell proliferation; liquid crystal elastomer; liquid crystals; tissue engineering.

Figure 1

Schematic organization of rod-like molecules in liquid crystal (LC) phases. Reprinted with permission from Reference [4] Copyright 2007 Royal Society of Chemistry.

Figure 2

Scheme representation of examples of side-chain and main chain elastomers (A) end-on main chain; (B) side-on side-chain; and (C) end-on side-chain liquid crystal elastomers (LCEs). Reprinted with permission from Reference [11], Copyright 2017 ACS Books.

Figure 3

The concept of LCEs as artificial actuator for mimicking muscle. Reprinted with permission from Reference [40]. Copyright 2010, Wiley ACH Advanced Materials.

Figure 4

Snapshots pictures taken during the actuation of the LCE microvalve developed by Sanchez-Ferrer et al. The working temperature is T_N/I = 80.5 °C. Reprinted with permission from Reference [57]. Copyright 2011, Wiley ACH Advanced Materials.

Figure 5

(a) The trans-cis isomerization of azobenzene, reprinted with permission from Reference [63]. Copyright 2013, MDPI Materials; (b) schematic depiction of nematic-isotropic phase transformation in a LC containing photo-isomerizable mesogenic molecules, which turn from a rod-like trans to a kinked cis conformation under ultraviolet (UV) irradiation. Reprinted with permission from Reference [64]. Copyright 2002, APS Physical Reviews E.

Figure 6

Contraction in a monodomain side-on nematic azo LCE film between (a) initial state (before irradiation); and (b) under UV irradiation (background in graduated paper). Reprinted with permission from Reference [65], Copyright 2003, Wiley ACH, Advanced Materials.

Figure 7

(a) Primary human dermal fibroblast (hDF) cultures grown for 5 days on 4LCE-α, grown in film LCE films, reprinted with permission from Reference [103], Copyright 2017 WILEY-VCH Macromolecular Bioscience; and (b) fluorescence confocal microscopy images of myoblast cells (C2C12) cultured in LCE foam stained with DAPI (for cell nuclei), 2D images stacked in z direction. Scale units are in μm. Reprinted with permission from Reference [118] Copyright 2016, ACS Macro Letters.