Abstract
Three-dimensional (3D) bioprinting is an emerging and promising technology in tissue engineering to construct tissues and organs for implantation. Alignment of self-assembly cell spheroids that are used as bioink could be very accurate after droplet ejection from bioprinter. Complex and heterogeneous tissue structures could be built using rapid additive manufacture technology and multiple cell lines. Effective vascularization in the engineered tissue samples is critical in any clinical application. In this review paper, the current technologies and processing steps (such as printing, preparation of bioink, cross-linking, tissue fusion and maturation) in 3D bio-printing are introduced, and their specifications are compared with each other. In addition, the application of ultrasound in this novel field is also introduced. Cells experience acoustic radiation force in ultrasound standing wave field (USWF) and then accumulate at the pressure node at low acoustic pressure. Formation of cell spheroids by this method is within minutes with uniform size and homogeneous cell distribution. Neovessel formation from USWF-induced endothelial cell spheroids is significant. Low-intensity ultrasound could enhance the proliferation and differentiation of stem cells. Its use is at low cost and compatible with current bioreactor. In summary, ultrasound application in 3D bio-printing may solve some challenges and enhance the outcomes.
Highlights
Since the first successful kidney transplant was performed in 1954 [1], organ transplantation has become a popular procedure for many incurable diseases
The waiting list for organ transplantation in the USA has more than 60,000 patients for kidney transplants, 3000 for heart, and 17,000 for liver, among who 17 will die every day according to data from the U.S Department of Health and Human Services
The introduction of fibrin-hyaluronic acid (HA) shows more accumulation of sulfated glycosaminoglycans (GAGs) and high efficiency in promoting chondrogenic differentiation and cartilage matrix synthesis of mesenchymal stem cells (MSCs) in vitro than the alginate group. Mechanical stimulation, such as cyclic compressive loading produced by low-intensity ultrasound (LIUS), can induce chondrogenic differentiation in MSCs [114,115], and enhance the viability of MSCs, increase the integrity of the differentiated tissues, and delay hypertrophic changes during differentiation as and mechanical factors
Summary
Since the first successful kidney transplant was performed in 1954 [1], organ transplantation has become a popular procedure for many incurable diseases. Recent advances in 3D bio-printing or the biomedical application of rapid prototyping have enabled precise positioning of biological materials, biochemicals, living cells, macrotissues, organ constructs, and supporting components (“bioink”) layer-by-layer in sprayed tissue fusion permissive hydrogels (“biopaper”) additively and robotically into complex 3D functional living tissues to fabricate 3D structures. This “bottom-up” solid scaffold-free automatic and biomimetic technology offers scalability, reproducibility, mass production of tissue engineered products with several cell types with high cell density and effective vascularization in large tissue constructs, even in situ organ biofabrication, which greatly relies on the principles of tissue self-assembly by mimicking natural morphogenesis [20].
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