A guide to the manufacture of sustainable, ready to use in vitro platforms for the electric-field pacing of cellularised 3D porous scaffolds

Electrical activity is a key feature of most native tissues, with the most notable examples being the nervous and the cardiac systems. Modern medicine has moved towards the mimicking and regenerations of such systems both with in vitro models and therapies. Although researchers have now an increased repertoire of cell types and bio-physical cues to generate increasingly complex in vitro models, the inclusion of novel biomaterials in such systems has been negligible, with most approaches relying on scaffold-free self-assembling strategies. However, the rapid development of functional biomaterials and fabrication technologies - such as electroconductive scaffolds - warrants consideration and inclusion of materials, with recent evidence supporting the benefit of incorporating electrically active materials and their influence on the maturation of cardiac cells and tissues. In order to be manipulated in bioreactor systems, scaffold-based in vitro models require bespoke rig and bioreactors that vary from those commonly used for scaffold-free systems. In this work, we detail methods to rapid prototype an electrical pacing bioreactor and R3S - a Rig for Stimulation of Sponge-like Scaffolds. As a proof of concept and validation we demonstrate that these systems are compatible with isotropic and anisotropic porous scaffolds composed of collagen or poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS). External pacing of C3H10 cells on anisotropic porous scaffolds led to a metabolic increase and enhanced cell alignment. This setup has been designed for pacing and simultaneously live tracking of in vitro models. This platform has wide suitability for the study of electrical pacing of cellularized scaffolds in 3D in vitro cultures.