Hydrogels such as alginate and gelatin have shown potential as biomaterials in various three-dimensional (3D) bioprinting applications. However, parameters such as viscosity, porosity, and printability influence the performance of hydrogel-based biomaterials, and there are limited characterization studies conducted on the behavior of these constructs. In this work, a syringe-based extrusion bioprinter was used to print 3D constructs with bioink composed of various concentrations of alginate and gelatin along with fibrinogen and human umbilical vein endothelial cells. Instead of crosslinking the gelatin, the gelatin was left uncrosslinked to provide microporosity within the system that can impact the cellular response. Mechanical and biochemical characterization was performed to evaluate the structural stability and integrity of the printed constructs along with viability of embedded cells. Bioprinted constructs of a higher total concentration of alginate and gelatin yielded better stability and structural integrity after culture. More importantly, higher amounts of gelatin (i.e., 1:9 instead of 2:3 alginate:gelatin) were shown to improve printability, which is different than most studies that instead use alginate to improve printability. In addition, higher amounts of gelatin impacted the changes in surface morphological features of the constructs after incubation, and ultimately improved biocompatibility with our system. Overall, this study demonstrated that an uncrosslinked gelatin system can provide flexible printing parameters and surface morphologies, but careful control over the printing parameters may be required. The bioink concentration of 10% (w/v) with minimum alginate and higher gelatin concentration exhibited the best printability, cell survival, and viability.

Bioprinting is a technique of creating 3D cell-laden structures by accurately dispensing biomaterial to form complex synthetic tissue. The printed constructs aim to mimic the native tissue by preserving the cell functionality and viability within the printed structure. The 3D bioprinting system presented in this paper aims to facilitate the process of 3D bioprinting through its ability to control the environmental parameters within an enclosed printing chamber. This design of the bioprinter targets to eliminate the need for a laminar flow hood, by regulating the necessary environmental conditions important for cell survival, especially during long duration prints. A syringe-based extrusion (SBE) deposition method comprising multiple nozzles is integrated into the system. This allows for a wider selection of biomaterials that can be used for the formation of the extracellular matrix (ECM). Tissue constructs composed of alginate-gelatin hydrogels were mixed with fibrinogen and human endothelial cells which were then characterized and compared using two methodologies: casted and bioprinted. Furthermore, vasculature was incorporated in the bioprinted constructs using sacrificial printing. Structural and functional characterization of the constructs were performed by assessing rheological, mechanical properties, and analyzing live-dead assay measurements.

The impact of magnetic fields on cellular function is diverse but can be described at least in part by the Radical Pair Mechanism (RPM), where magnetic field intervention alters reactive oxygen species (ROS) populations and downstream cellular signaling. Here, cellular magnetophoresis within three-dimensional scaffolds was monitored in an applied oscillating 1.4 MHz radiofrequency (RF) magnetic field with an amplitude of 10 micro Tesla and a static 50 micro Tesla magnetic field. Given that cellular respiration or glycolysis can be increased based on the orientation of the RF magnetic field, this study focused on the parallel orientation to increase ATP synthesis. Results suggest that RF accelerated clustering and elongation after 1 day with increased levels of clustering and cellular linkage after 7 days. Electron microscopy provided additional topological information and verified the development of fibrous networks and extracellular matrix were visualized after 7 days in samples maintained in RF. Analysis of the distribution of cells within the scaffolds revealed that the clustering rate during the first day was increased nearly five times in the RF environment. This work demonstrates time-dependent cellular magnetophoresis that may be influenced by quantum biology (QB) processes and signaling that can further attenuate or enhance cellular bioenergetics and behavior.