Engineering soft polymers for static and dynamic cell culture platforms

Abstract

In vitro cardiac models have been attracted substantial interest in cardiac tissue engineering (TE). They provide a promising alternative to the drug screening process currently in use which suffer from high failure rate in clinical trials. Engineering these systems requires a combination of biomaterials and technologies to design scaffolds that accurately replicate the environment of the native tissue.

In this work, polymers that can statically or dynamically stimulate cardiac cells in vitro have been investigated. Elastomers and hydrogels were considered as the most appropriate materials especially for their elastic properties. However, shaping these materials using conventional microfabrication techniques is extremely difficult.

In static conditions, Parylene C was employed as a mask material to pattern polydimethylsiloxane (PDMS) and polyacrylamide (PAm) hydrogel. Microfabrication strategies were used to provide hybrid anisotropic topographies and biochemical micropatterns on scaffolds. The results demonstrated the potential of using Parylene C as a template for soft polymers especially in the reproduction of the fabrication process, and in the stability of the patterns on the moulded replica. The compatibility of these constructs was demonstrated with neonatal rat cardiac myocytes (NRVMs). Evidence confirmed the possibility of using these constructs for future in vitro models.

The dynamic approach explored the stimulation of cells in a more realistic environment. Herein, electro-active hydrogels (EAHs) have been intentionally produced and designed with specific properties related to their size, surface properties, and chemistry. Firstly, the synthesis and electro-actuation of hydrolysed PAm (hPAm) hydrogel were performed. Experimental observations revealed practical drawbacks that limited the processing of this hydrogel at the micro-scale. Colloidal solutions made of the copolymer and interpenetrating networks (IPN) based on Poly (N-isopropylacrylamide) (PNIPAm) and poly (acrylic acid) (PAAc) nanogels provided an alternative solution to obtain spin-coatable thin films controllable in thickness. Finally, the bio-compatibility of the films with cells suggested future improvements in the synthesis and microfabrication of EAHs.

The main findings of this work revealed Parylene C as an excellent candidate to anisotropically pattern soft scaffolds with reproducible features at the micro- and nano-scale. Among them, PAm hydrogel was more successful in promoting cardiac cell elongation and calcium activity. For dynamic scaffolds,hPAm showed a planar expansion under a DC electric field of 0.03 V/mm, but this material was not suitable for microfabrication and cell culturing. Finally, it was demonstrated that to have spin-coatable hydrogels colloids are more appropriate, and films with a thickness ranging from 100 nm to 300 nm were obtained. Although these results were prominsing, further investigations are required for electro-actuation and cell culturing.

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Identifiers

ORCID for Hywel Morgan: orcid.org/0000-0003-4850-5676

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