3D-printable conductive materials for tissue engineering and biomedical applications

Many patients that undergo autografting suffer from donor site morbidity and risk of immune rejection. Tissue engineering is receiving considerable attention as engineered tissues could help overcome the drawbacks of autografts and achieve better performance on tissue repair, replacement and regeneration. Conductivity is one of the desired properties of engineered scaffolds and tissue constructs as bioelectricity plays an important role in the native physiological environment. Hence, conductive materials have been extensively used in the making of biosensors, tissue engineering scaffolds and drug delivery systems to elicit electrically-mediated signals, thus mimicking the natural cellular environment. Conductive polymers, carbon-based materials, and metal nanoparticles are the main categories of conductive materials used. Ionic liquids, especially biocompatible ionic liquids, is currently being explored as a competitive filler composite to greatly improve the conductivity of polymers with little to zero cytotoxicity. The effects of electrical stimulation on cell alignment, migration, proliferation, and differentiation as well as detailed properties of different types of conductive materials are briefly yet succinctly reviewed. Furthermore, 3D printing of conductive scaffolds and hydrogels, and their corresponding biomedical applications are also discussed.