Multifunctional Electroactive 3D-Printed Scaffolds with Polypyrrole-Based Coatings for Biomedical Applications

Several intrinsic electroconductive polymers have been studied for tissue engineering and biomedical applications, as they can mimic the cell microenvironment of some electroactive tissues and have body-sensing capacity. However, these polymers often lack good processability and biocompatibility, complicating the development of appropriate biomaterials or devices such as cell scaffolds and biosensors. To overcome these issues, a two-step method was introduced to coat 3D-printed poly (ε-caprolactone) (PCL) scaffolds with intrinsic electroconductive polypyrrole (PPy) and gelatin (GEL). Compared to pure 3D-printed PCL, the coated hybrid scaffolds exhibited 12 orders of magnitude higher electrical conductivity, ionic conduction capacity, rougher topography, and even a 5% higher compressive strength while maintaining the main properties of PCL. The proliferation of human mesenchymal stem cells (hMSCs) was 13% higher in the PPy-coated scaffolds after 14 days, further exhibiting rounded cell morphologies, unlike the flattened shapes seen on the PCL controls. The high conductivity of the scaffolds produced by our two-step methodology further allows their use as electrodes for electromyogram measurement and piezoresistive sensors. Noteworthy, the coated biomaterials can be used as a triboelectric nanogenerator (TENG), achieving an output power density of 4-6 mW m⁻² under the mechanical contact-separation stimulus. These findings highlight the potential application of our approach for developing multifunctional electroactive PPy-coated PCL biomaterials for tissue engineering, biosensing, piezoresistive sensors, and TENG.