The impact of mechanical tuning on the printability of decellularized amniotic membrane bioinks for cell-laden bioprinting of soft tissue constructs

Decellularized extracellular matrix (dECM) bioinks hold significant potential in the 3D bioprinting of tissue-engineered constructs (TECs). While 3D bioprinting allows for the creation of custom-designed TECs, the development of bioinks based solely on dAM, without the inclusion of supporting agents or chemical modifications, remains underexplored. In this study, we present the concentration-dependent printability and rheological properties of dAM bioinks, along with an analysis of their in vitro cellular responses. Our findings demonstrate that increasing dAM concentrations, within the range of 1 to 3% w/v, enhances the mechanical moduli of the bioinks, enabling the 3D printing of flat structures with superior shape fidelity. In vitro assays reveal high cell viability across all dAM bioink formulations; however, at 3% w/v, the bioink tends to impede fibroblast proliferation, resulting in round cell morphology. We propose that bioinks containing 2% w/v dAM strike an optimal balance, providing fine-resolved features and a supportive microenvironment for fibroblasts, promoting elongated spindle-like morphology and enhanced proliferation. These results underscore the importance of dAM concentration in regulating the properties and performance of bioinks, particularly regarding cell viability and morphology, for the successful 3D bioprinting of soft tissues.