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Exploiting the unique properties of three‐dimensional (3D) auxetic scaffolds in tissue engineering and regenerative medicine applications provides new impetus to these fields. Herein, the results on the fabrication and characterization of 3D auxetic scaffolds for tissue engineering applications are presented. The scaffolds are based on the well‐known re‐entrant hexagonal geometry (bowtie) and they are fabricated by multiphoton lithography using the organic−inorganic photopolymer SZ2080. In situ scanning electron microscopy–microindentations and nanoindention experiments are employed to characterize the photocurable resin SZ2080 and the scaffolds fabricated with it. Despite SZ2080 being a stiff material with a positive Poisson's ratio, the scaffolds exhibit a negative Poisson's ratio and high elasticity due to their architecture. Next, mouse fibroblasts are used to seed the scaffolds, showing that they can readily penetrate them and proliferate in them, adapting the scaffold shape to suit the cells' requirements. Moreover, the scaffold architecture provides the cells with a predilection to specific directions, an imperative parameter for regenerative medicine in many cell‐based applications. This research paves the way for the utility of 3D auxetic metamaterials as the next‐generation adaptable scaffolds for tissue engineering. [ABSTRACT FROM AUTHOR]

Multiphoton lithography (MPL), based on multiphoton polymerization (MPP), is a powerful technique for the fabrication of 3D structures used in tissue engineering and other biomedical applications, microoptics, nanophotonics, micro‐/nanomechanics, and micro‐/nanofluidics. MPL is based on the localized polymerization/cross‐linking of photosensitive materials induced by femtosecond laser pulses. The use of an appropriate photoinitiator (PI) is required to initiate the polymerization/cross‐linking process. However, several studies have demonstrated the cytotoxicity of the PIs and their derived free radicals. The photo‐cross‐linking of a pre‐synthesized photosensitive gelatin methacrylamide (GelMA) biopolymer using an initiator‐free MPP process is reported for the first time. This is achieved by employing a femtosecond laser operating in the visible range of the spectrum (520 nm). It is demonstrated that multiphoton absorption can cause the cleavage of the polymer double bonds and induce the cross‐linking process. GelMA‐based 3D structures accurately replicating the original computer‐aided design are fabricated, and their excellent biocompatibility is demonstrated in vitro using 3D cell culture experiments with NIH‐3T3 fibroblast cells. Three‐dimensional structures based on gelatin methacrylamide are fabricated by initiator‐free multiphoton polymerization using a femtosecond laser operating in the visible range. The elimination of the toxic photoinitiator and its derived free radicals renders the approach very attractive in 3D scaffold fabrication. [ABSTRACT FROM AUTHOR]