Authors:

Torge Hartig¹, Wiebke Reichstein¹, Margarethe Hauck², Gabriel Chan¹, Mohammadreza Taale³, Christine Arndt³, Florian Rasch², Maximilian Burk¹, Thomas Strunskus¹, Christine Selhuber-Unkel³, Rainer Adelung², Franz Faupel¹, Stefan Schröder¹, Fabian Schütt²

Affiliations:

¹Chair for Multicomponent Materials, Institute of Materials Science, Kiel University, Kiel, Germany

²Functional Nanomaterials Chair, Institute of Materials Science, Kiel University, Kiel, Germany

³Institute for Molecular Systems Engineering, Heidelberg University, Heidelberg, Germany

Abstract:

Hydrogels are used in regenerative tissue engineering, e.g. as cell scaffolds, as their physical properties are similar to the properties of native soft tissue. For many applications their characteristics need to be tuned in various properties simultaneously to ensure the needed interaction with incorporated cells. In our chosen fabrication technique these properties, like stiffness and pore size, are not dependent on each other. Nano- and micro-engineering of hydrogels has recently shown great potential in order to specifically tailor the properties of hydrogels, e.g. by the incorporation of functional nanoparticles or by micro-structuring. [1]

Here we demonstrate a new, solvent-free approach to synthesize highly porous functional hydrogels, so-called aero-hydrogels by employing initiated chemical vapor deposition(iCVD) processes. iCVD can be used to conformally coat different kinds of porous structures with thin layers of polymers. [2,3] A prominent 3D network material mimicking the shape of extracellular matrix is fabricated by utilizing tetrapodal-shaped ZnO microparticles. This network is used as a sacrificial scaffold. [4] Hydrogel thin films are deposited via iCVD onto the structure and the T-ZnO network is etched away. A mechanically stable hydrogel network with more than 99% empty space can be created. The aero-hydrogel can be used as a cell scaffold where pore size, crosslinking, thickness and stiffness can independently be tuned towards the needs of the respective type of cells, while showing remarkable mechanical stability. In multilayers electrical conductivity can be incorporated into the aero-hydrogel while the surface properties in the aero material are determined by the hydrogel.

References:

[1] Arndt, Christine, et al. "Microengineered Hollow Graphene Tube Systems Generate Conductive Hydrogels with Extremely Low Filler Concentration." Nano letters (2021): 3690-3697.

[2] Reichstein, Wiebke, et al. "Initiated Chemical Vapor Deposition (iCVD) Functionalized Polylactic Acid–Marine Algae Composite Patch for Bone Tissue Engineering." Polymers (2021): 186.

[3] Aktas, Oral Cenk, et al. "Superhydrophobic 3D porous PTFE/TiO2 hybrid structures." Advanced Materials Interfaces (2019): 1801967.

[4] Mishra, Yogendra Kumar, and Rainer Adelung. "ZnO tetrapod materials for functional applications." Materials Today (2018): 631-651.