Three-Dimensional Printable Conductive Semi-Interpenetrating Polymer Network Hydrogel for Neural Tissue Applications

Abstract

Intrinsically conducting polymers (ICPs) are widely used to fabricate biomaterials; their application in neural tissue engineering, however, is severely limited because of their hydrophobicity and insufficient mechanical properties. For these reasons, soft conductive polymer hydrogels (CPHs) are recently developed, resulting in a water-based system with tissue-like mechanical, biological, and electrical properties. The strategy of incorporating ICPs as a conductive component into CPHs is recently explored by synthesizing the hydrogel around ICP chains, thus forming a semi-interpenetrating polymer network (semi-IPN). In this work, a novel conductive semi-IPN hydrogel is designed and synthesized. The hybrid hydrogel is based on a poly( N -isopropylacrylamide- co - N -isopropylmethacrylamide) hydrogel where polythiophene is introduced as an ICP to provide the system with good electrical properties. The fabrication of the hybrid hydrogel in an aqueous medium is made possible by modifying and synthesizing the monomers of polythiophene to ensure water solubility. The morphological, chemical, thermal, electrical, electrochemical, and mechanical properties of semi-IPNs were fully investigated. Additionally, the biological response of neural progenitor cells and mesenchymal stem cells in contact with the conductive semi-IPN was evaluated in terms of neural differentiation and proliferation. Lastly, the potential of the hydrogel solution as a 3D printing ink was evaluated through the 3D laser printing method. The presented results revealed that the proposed 3D printable conductive semi-IPN system is a good candidate as a scaffold for neural tissue applications.

3D-Printable Hierarchical Nanogel-GelMA Composite Hydrogel System

“…The printed hydrogel presented homogeneity and stability after UV cross-linking, and maintained the hexagram shape after dehydration for a few minutes in air. These results further confirmed that the prepared MA-NG-GelMA ink is 3D-printable, and that these kinds of hybrid approaches of ink formation are an upcoming new trend to create more functional hydrogel systems [38].…”

Advanced Metallic and Polymeric Coatings for Neural Interfacing: Structures, Properties and Tissue Responses

“…A 3D printing technique has also been used for the construction of advanced microstructured hydrogels which are suitable for neural electrode coatings. The typical 3D printing methods of hydrogel include inkjet printing [221], light-based printing [222] and extrusion-based printing [223]. For example, Jiang et al fabricated a three-dimensional collagen/silk fibroin scaffold which can support the adhesion, elongation and differentiation of neural stem cells in vitro, and can promote the repair of injured the spinal cords of rats in vivo [224].…”

“…The cell culture studies demonstrated that, compared to the pure nanocellulose, cells cultured on the conductive guidelines printed by the nanocellulose-based ink exhibited better proliferation and differentiation, which were probably induced by the ink's conductive property [225]. Rinoldi et al designed a soft, biocompatible and conductive semi-IPN hydrogel which can improve the survival rates of neurons and astrocytes [222]. This hydrogel-as a 3D-printing ink-could be fabricated into micro-objects, which denotes a promising potential for novel neural tissue engineering applications.…”

Hydrogel, Electrospun and Composite Materials for Bone/Cartilage and Neural Tissue Engineering

“…In other studies, a non-commercial hydrogel with interesting properties from the neural tissue engineering point of view was designed. Rinoldi et al [107] synthesized a smart conductive semi-interpenetrating polymer network (semi-IPN) poly(N-isopropylacrylamideco-N-isopropylmethacrylamide)(P(NIPAm-co-NIPMAm))/polythiophene-based hydrogel for regeneration of neural tissues. Compared to pure (P(NIPAm-co-NIPMAm) hydrogel, the composite material showed three-fold decreased impedance, corresponding to increased electrical properties.…”