# Trends and Technological Challenges of 3D Bioprinting in Cultured Meat: Technological Prospection
## 4 Discussion
### Biofabrication of Cultured Meat
#### 4.3.4 3D Bioprinting  
Three-dimensional bioprinting is one of the most promising technologies with which to biofabricate scaffolds for tissue engineering, both for regenerative medicine and for the food sector, and especially with respect to the biofabrication of cultured meat [97]. The main 3D bioprinting techniques used for the biofabrication of scaffolds loaded with cells are extrusion, jetting, and Vat photopolymerization. The extrusion-based bioprinting technique can be pneumatically driven (air pressure) or mechanically driven (piston or screw). This technique is the most commonly used for various applications in tissue engineering due to its versatility and wide availability [98]. The main advantages of the extrusion-based method are its scalability and ability to print a wide range of high-viscosity materials and high cell concentrations [99]. However, high-viscosity fluids are the most suitable for this technique, providing adequate mechanical support for 3D scaffolds [100]. The jetting-based bioprinting technique is capable of printing biological materials with optimized speed, accuracy, and resolution [101]. Despite its advantages, this technique can only be used for low-viscosity materials, which leads to a tendency towards nozzle clogging [102]. In vat photopolymerization-based bioprinting, noted for its stereolithography technique, it is possible to obtain 3D scaffolds with high speed and high resolution [59]. This technique is based on the polymerization of light-sensitive polymers. UV radiation used in conventional stereolithography can be harmful to cells and can trigger mutations [103]. In common, these 3D bioprinting techniques have limitations according to the properties of the bioinks, such as their viscosity, directly impacting the bioprinting quality of the material [100; 104; 105]. Despite the numerous advantages of 3D bioprinting, the success of this technology depends directly on a few factors, including the biomaterial properties, the crosslinking process, print fidelity, stability, and cell viability, as well as the physical, mechanical, and rheological properties of bioinks [106; 107]. One of the most challenging properties in the 3D bioprinting process is cell viability. In addition to the technical challenges, 3D bioprinting presents ethical issues that need to be addressed, such as intellectual property issues, safety regulations, and concerns about misuse of the technology [108]. In the extrusion-based bioprinting process, the bioink is extruded through a needle under pressure, which can cause shear stresses between the bioink and the wall of the printing nozzle. If these stresses exceed a specific limit, they can rupture cell membranes, causing reduced cell viability [109]. [PERSON] et al. [110] used computational simulation to evaluate the maximum shear stress during the extrusion-based bioprinting process. They concluded that in addition to the shear stress that normally occurs in the printing process, the geometry of the nozzle also influences cell viability. In the jetting-based bioprinting process, there are few detailed studies on the impact of droplet velocity and volume on cell viability. [PERSON] et al. [111] used a thermal inkjet bioprinting system to evaluate the influence of drop impact speed and drop volume on cell viability and proliferation. They observed that increasing the concentration of cells in the bioink resulted in slower droplet impact speed, providing greater cell viability and improved print quality by reducing droplet splatter. It was concluded that due to the limited use of biomaterials compatible with the method, in addition to its photopolymerization process, the control of impact velocity and droplet evaporation directly influences cell proliferation and viability [16]. The cross-linking process is another fundamental factor for 3D bioprinting and is directly related to the mechanical properties of 3D structures, as well as to the gelation kinetics, post-print structure fidelity, and viability of encapsulated cells [112].