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Bioprinting has attracted extensive attention in the field of tissue engineering due to its unique capability in constructing biomimetic tissue constructs in a highly controlled manner. However, it is still challenging to reproduce the physical and structural properties of native electroactive tissues due to the poor electroconductivity of current bioink systems as well as the limited printing resolution of conventional bioprinting techniques. In this work, an electro‐conductive hydrogel is prepared by introducing poly (3,4‐ethylene dioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) into an RGD (GGGGRGDSP)‐functionalized alginate and fibrin system (RAF), and then electrohydrodynamic (EHD)‐bioprinted to form living tissue constructs with microscale resolution. The addition of 0.1 (w/v%) PEDOT: PSS increases the electroconductivity to 1.95 ± 0.21 S m−1 and simultaneously has little effect on cell viability. Compared with pure RAF bioink, the presence of PEDOT: PSS expands the printable parameters for EHD‐bioprinting, and hydrogel filaments with the smallest feature size of 48.91 ± 3.44 µm can be obtained by further optimizing process parameters. Furthermore, the EHD‐bioprinted electro‐conductive living tissue constructs with improved resolution show good viability (>85%). The synergy of the advanced electro‐conductive hydrogel and EHD‐bioprinting presented here may provide a promising approach for engineering electro‐conductive and cell‐laden constructs for electroactive tissue engineering.

Background Osteoarthritis (OA) is a common degenerative disease. Chondrocyte dedifferentiation can accelerate the progress of OA. Three-dimensional printing (3DP) is widely used in tissue regeneration applications. A three-dimensional (3D) culture system with 3D printed scaffolds could reduce the dedifferentiation of chondrocytes during passages, which would be a potential method for chondrocyte expansion. Methods The viability and proliferation of chondrocytes on scaffolds and effects of scaffolds with 100, 150, 200, 250 or 300 µm spacing on chondrocyte dedifferentiation were analyzed in vitro . The morphology of scaffolds and cell/scaffold constructs was observed by scanning electron microscopy (SEM). Glycosaminoglycan (GAG) was evaluated by Alcian blue staining. The effects of different spacing on chondrocyte dedifferentiation were evaluated by the messenger RNA (mRNA) and protein levels of cartilage-related genes. Results With more binding sites, the proliferation and viability of chondrocytes on scaffolds with 100 and 150 µm spacing were better than those with 200, 250 and 300 µm spacing on day 1, but this advantage diminished over time. The histology and quantitative real-time polymerase chain reaction (qRT-PCR) results showed that 200 µm spacing inhibits chondrocyte dedifferentiation better. Conclusions 3D printed scaffolds with 200 µm spacing can inhibit chondrocyte dedifferentiation, providing a basis for the future study of 3D printed scaffolds as an effective method for chondrocyte expansion.

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