3D printable electroconductive gelatin‑hyaluronic acid materials containing polypyrrole nanoparticles for electroactive tissue engineering

Electrically conductive bio-scaffolds are explored in the field of tissue engineering (TE) as a solution to address the clinical need of electroactive tissues, finding applications in nervous, cardiac, and spinal cord injury repair. In this work, we synthesise polypyrrole nanoparticles (PPy NP) via the mini-emulsion method with further combination with a gelatin/hyaluronic acid (HA) hydrogel to create electroconductive Gel:HA:PPy-NP TE scaffolds. Electroconductive Gel:HA:PPy-NP scaffolds possess excellent mechanical properties at 1.08 ± 0.26 MPa, closely matching the reported mechanical performance of the spinal cord. Scaffolds were designed with controlled porosity of 526.2 ± 74.6–403.9 ± 57.4 μm, and conductivities of 4.3 × 10 – 6 ± 1.1 × 10 –6 S.cm −1 were reached. Rheological studies show that prior to lyophilisation, the Gel:HA:PPy-NP hydrogels
display a shear-thinning behaviour. These gels were subsequently 3D printed into predefined 2 layer lattice geometries and displayed excellent post-printing shape fidelity. In vitro studies show that the Gel:HA:PPy-NP scaffolds are cytocompatible with mesenchymal stem cells and neuronal stem cells and display encouraging cell attachment and proliferation profiles. Based on these results, the incorporation of PPy NPs into Gel:HA biomaterial scaffolds enhances the conductive capabilities of the material, while showcasing biocompatible behaviour with cell cultures. Hence, Gel:HA:PPy-NP scaffolds are a promising TE option for stimulating regeneration following nervous tissue injury.