Many properties in both healthy and pathological tissues are highly influenced by the mechanical properties of the extracellular matrix. Stiffness gradient hydrogels are frequently used for exploring these complex relationships in mechanobiology. In this study, the fabrication of a simple, cost‐efficient, and versatile system is reported for creation of stiffness gradients from photoactive hydrogels like gelatin‐methacryloyl (GelMA). The setup includes syringe pumps for gradient generation and a 3D printed microfluidic device for homogenous mixing of GelMA precursors with different crosslinker concentration. The stiffness gradient is investigated by using rheology. A co‐culture consisting of human adipose tissue‐derived mesenchymal stem cells (hAD‐MSCs) and human umbilical cord vein endothelial cells (HUVECs) is encapsulated in the gradient construct. It is possible to locate the stiffness ranges at which the studied cells displayed specific spreading morphology and migration rates. With the help of the described system, variable mechanical gradient constructs can be created and optimal 3D cell culture conditions can be experientially identified.

New carbohydrate-based ionic liquids are characterized, towards their thermal stability, biocompatibility and antimicrobial behavior. The results led to structure–property relationships and higher cell viabilities than most commercial ionic liquids.

This work presents enabling technologies for the optimization of the manufacturing of GelMA‐based hydrogels constructs with desired stiffness gradients. The manufacturing technique combines dynamic mixing for gradient generation and a passive micromixer for efficient hydrogel blending. A digital replica of the fabrication process is developed, integrating theoretical and computational models, as well as experimental data, in order to predict and control the stiffness profile obtained within the constructs. The workflow for the development of the in silico framework, based on rigorous verification, validation, and uncertainty quantification steps, is presented. The validation of the digital replica is based on reference settings of process variables, which result in constructs with an exponential stiffness profile. The developed in silico model has been employed for optimizing process variables in order to obtain a linear stiffness profile in the extruded construct without the need of expensive and time‐consuming trial‐and‐error procedures. The developed digital replica is now a powerful tool for the creation of hydrogel gradient constructs for tissue engineering applications or for the screening of optimal 3D cell culture conditions.

In vitro cultivation conditions play a crucial role in cell physiology and the cellular response to external stimuli. Oxygen concentrations represent an essential microenvironmental factor influencing cell physiology and behaviour both in vivo and in vitro. Therefore, new approaches are urgently needed to monitor and control oxygen concentrations in 2D and 3D cultures, as well as cell reactions to these concentrations. In this work, we modified two types of human endothelial cells–human microvascular (huMECs) and umbilical vein endothelial cells (huVECs) with genetically encoded hypoxia biosensors and monitored cell reactions in 2D to different oxygen concentrations. Moreover, we fabricated 3D cell spheroids of different cell numbers and sizes to reveal the onset of hypoxia in huVECs and huMECs. We could demonstrate a quantitative sensor response of two cell types to reduced oxygen supply in 2D and reveal different thresholds for hypoxic response. In 3D cell spheroids we could estimate critical construct sizes for the appearance of a hypoxic core. This work for the first time directly demonstrates different hypoxic signatures for huVECs and huMECs in 2D and 3D cell culture systems.