A microvalve‐based bioprinting system for the manufacturing of high‐resolution, multimaterial 3D‐structures is reported. Applying a straightforward fluid‐dynamics model, the shear stress at the nozzle site can precisely be controlled. Using this system, a broad study on how cell viability and proliferation potential are affected by different levels of shear stress is conducted. Complex, multimaterial 3D structures are printed with high resolution. This work pioneers the investigation of shear stress‐induced cell damage in 3D bioprinting and might help to comprehend and improve the outcome of cell‐printing studies in the future.

The mechanical and physicochemical effects of three-dimensional (3D) printable hydrogels on cell behavior are paramount features to consider before manufacturing functional tissues. We hypothesize that besides good printability and cytocompatibility of a supporting hydrogel for the manufacture of individual tissues, it is equally essential to consider beforehand the desired tissue (bone, cartilage, fat). In light of its application, the structure and stiffness of printable hydrogel matrices influence cell geometry, which in turn impacts the differentiation fate. Embedded human mesenchymal stromal cells in printable type I collagen- and chitosan–agarose blends were induced to differentiate toward osteoblasts and adipocytes. Hydrogels' printability in air versus submerged printing in perfluorocarbon was evaluated according to the height, diameter, uniformity, and stability of 3D printed vertical cylinders. Bipotent differentiation within hydrogels was assessed histologically (morphology, cellularity), by immunohistochemistry (vimentin, smooth muscle actin), two-photon microscopy (spatial distribution), and real-time polymerase chain reaction (ALP, BGLAP, OPN, RUNX2, COL 1, aP2, PPARγ-2). Agarose and agarose blends revealed the most valid printability properties by generating uniform cylinders with an average height of 4 mm. Osteogenic differentiation was preferably achieved in anisotropic soft collagen-rich substrates, whereas adipogenic differentiation mostly occurred in isotropic stiff agarose-rich matrices. The conjugation of type I collagen to agarose with varying ratios is possibly a suitable bioink for a broad range of 3D printed mesenchymal tissues.

Over the last decade, bioprinting technologies have begun providing important tissue engineering strategies for regenerative medicine and organ transplantation. The major drawback of past approaches has been poor or inadequate material-printing device and substrate combinations, as well as the relatively small size of the printed construct. Here, we hypothesise that cell-laden hydrogels can be printed when submerged in perfluorotributylamine (C(12)F(27)N), a hydrophobic high-density fluid, and that these cells placed within three-dimensional constructs remain viable allowing for cell proliferation and production of extracellular matrix. Human mesenchymal stem cells and MG-63 cells were encapsulated into agarose hydrogels, and subsequently printed in high aspect ratio in three dimensional structures that were supported in high density fluorocarbon. Three-dimensional structures with various shapes and sizes were manufactured and remained stable for more than six months. Live/dead and DAPI stainings showed viable cells 24 h after the printing process, as well as after 21 days in culture. Histological and immunohistochemical analyses after 14 and 21 days revealed viable cells with marked matrix production and signs of proliferation. The compressive strength values of the printed gels consequently increased during the two weeks in culture, revealing encouraging results for future applications in regenerative medicine.