3D bioprinting for tissue engineering: Stem cells in hydrogels

Abstract

Surgical limitations require alternative methods of repairing and replacing diseased and damaged tissue. Regenerative medicine is a growing area of research with engineered tissues already being used successfully in patients. However, the demand for such tissues greatly outweighs the supply and a fast and accurate method of production is still required. 3D bioprinting offers precision control as well as the ability to incorporate biological cues and cells directly into the material as it is being fabricated. Having precise control over scaffold morphology and chemistry is a significant step towards controlling cellular behaviour, particularly where undifferentiated cells, i.e., stem cells, are used. This level of control in the early stages of tissue development is crucial in building more complex systems that morphologically and functionally mimic in vivo tissue. Here we review 3D printing hydrogel materials for tissue engineering purposes and the incorporation of cells within them. Hydrogels are ideal materials for cell culture. They are structurally similar to native extracellular matrix, have a high nutrient retention capacity, allow cells to migrate and can be formed under mild conditions. The techniques used to produce these materials, as well as their benefits and limitations, are outlined.

A 3D bioprinted in situ conjugated‐co‐fabricated scaffold for potential bone tissue engineering applications

“…8 The properties of the scaffold depend mainly on the fabrication methods and the nature of the biomaterial .6 Twodimensional (2 D) patterns of biochemical and mechanical cues have been generated through the development of numerous intricate methods, but for many cell types, the 2D culture condition may not be appropriate for propagating tissue regeneration. 11 The advantages of 3D printed scaffolds for bone tissue engineering include the fabrication of a well-defined architecture with patient-specific geometries as well as enabling the necessary spatial organization (e.g., of bioactives or cells) within the scaffold for enhancing biological functionality. 7 Scaffolds with controlled surface chemistry, pore size distribution, pore volume, pore interconnectivity, and architecture cannot be fabricated with traditional processing techniques 9,10 such as solvent casting or particle leaching, freeze-drying, and gas foaming.…”

Advancing Frontiers in Bone Bioprinting

“…Separate printing can also be used for producing a reinforcement structure from one outlet and a cell‐laden hydrogel from a second outlet . Recently, stereolithography (SLA) was used to incorporate cells into printed structures . SLA involves the use of a focused ultraviolet (UV) light beam on a liquid photopolymer, leading to polymer crosslinking and layer‐by‐layer printing .…”

Recent Advances in Enabling Technologies in 3D Printing for Precision Medicine

“…Many exciting advances in the use of bioactive components for precision medicine have already been implemented in clinical settings for non‐3D printing applications, such as personalized gene therapies or matrix‐induced autologous chondrocyte implantation . Further, advances in gene therapy, cell culture, and cell manufacturing offer an array of exciting new components to incorporate into bioinks for precision medicine . While not the focus of this progress report, design of these inks, which can be broken into further discrete unit operators, has been detailed in previous reviews …”