Liquid crystal elastomer foams with elastic properties specifically engineered as biodegradable brain tissue scaffolds.

Tissue regeneration requires 3-dimensional (3D) smart materials as scaffolds to promote transport of nutrients. To mimic mechanical properties of extracellular matrices, biocompatible polymers have been widely studied and a diverse range of 3D scaffolds have been produced. We propose the use of responsive polymeric materials to create dynamic substrates for cell culture, which goes beyond designing only a physical static 3D scaffold. Here, we demonstrated that lactone- and lactide-based star block-copolymers (SBCs), where a liquid crystal (LC) moiety has been attached as a side-group, can be crosslinked to obtain Liquid Crystal Elastomers (LCEs) with a porous architecture using a salt-leaching method to promote cell infiltration. The obtained SmA LCE-based fully interconnected-porous foams exhibit a Young modulus of 0.23 ± 0.07 MPa and a biodegradability rate of around 20% after 15 weeks both of which are optimized to mimic native environments. We present cell culture results showing growth and proliferation of neurons on the scaffold after four weeks. This research provides a new platform to analyse LCE scaffold-cell interactions where the presence of liquid crystal moieties promotes cell alignment paving the way for a stimulated brain-like tissue.

Synthetic approach to tailored physical associations in peptide-polyurea/polyurethane hybrids.

Nature has achieved diverse functionality via hierarchical organization driven by physical interactions such as hydrogen bonding. Synthetically, polymer-peptide hybrids have been utilized to achieve these architectural arrangements and obtain diverse mechanical properties, stimuli responsiveness, and bioactivity. Here, we explore the impact of peptide ordering and soft/hard phase interactions in PEG-based non-chain extended and chain extended peptidic polyurea (PU) and polyurea/polyurethane (PUU) hybrids towards tunable mechanics. Increasing the peptide content of poly(ε-carbobenzyloxy-l-lysine) (PZLY) revealed an increase in α-helical formation and modulation in amine/ether hydrogen bonding, suggesting enhanced intermolecular hydrogen bonding between peptide segments and soft/hard blocks. A balance of phase mixing and microphase segregation was observed depending on competitive hydrogen bonding and the hybrid architecture. This phase behaviour strongly modulated the mechanical response, particularly modulus and extensibility. We anticipate that this solid-state, synthetic framework will expand the reach of our peptide hybrids into biointerfacing materials, including scaffolds and responsive actuators via peptide selection.

Programming shape and tailoring transport: advancing hygromorphic bilayers with aligned nanofibers.

Natural systems utilize nanofiber architectures to guide water transport, tune mechanical properties, and actuate in response to their environment. In order to harness these properties, a hygromorphic bilayer composite comprised of a self-assembled fiber network and an aligned electrospun fiber network was fabricated. Molecular gel self-assembly was utilized to increase hydrophobicity and strength in one layer, while aligned electrospun poly(vinyl alcohol) (PVA) nanofibers increased the rate of hydration and facilitated tunable actuation in the other. Interfacing these two fiber networks in a poly(ethylene oxide-co-epichlorohydrin) (EO-EPI) matrix led to hydration-driven actuation with tunable curvature. Specifically, variations in fiber alignment were achieved by cutting at 0, 90, and 45 degree angles in relation to the length edge of the composite. Along with the ability to program the natural curvature, the utilization of aligned nanofibers increased water transport compared to random nanofiber systems, resulting in a reduction in response time from 20+ minutes to 2-3 minutes.