Organ printing
[7] Progress continued in 1999 when the first artificial organ made using bioprinting was printed by a team of scientist leads by Dr. Anthony Atala at the Wake Forest Institute for Regenerative Medicine.
[9] In fact, scientists at the Warsaw Foundation for Research and Development of Science in Poland have been working on creating a fully artificial pancreas using bioprinting technology.
As the rapid manufacturing techniques entailed by 3D printing become increasingly efficient, their applicability in artificial organ synthesis has grown more evident.
Sacrificial writing into function tissue (SWIFT) is a method of organ printing where living cells are packed tightly to mimic the density that occurs in the human body.
[2] This method of organ printing uses spatially controlled light or laser to create a 2D pattern that is layered through a selective photopolymerization in the bio-ink reservoir.
For instance, alginate polymerization is started by calcium ions in the substrate, which diffuse into the liquified bioink and permit for the arrangement of a strong gel.
Extrusion bioprinting is frequently coupled with UV light, which photopolymerizes the printed fabric to create a more steady, coordinated construct.
Additionally, most of the parts printed by FDM are typically composed from the same thermoplastics that are utilized in tradition injection molding or machining techniques.
[16] Recent advances in organ printing using SLS include 3D constructs of craniofacial implants as well as scaffolds for cardiac tissue engineering.
Due to the nature of 3D printing, materials used must be customizable and adaptable, being suited to wide array of cell types and structural conformations.
[17] Materials for 3D printing usually consist of alginate or fibrin polymers that have been integrated with cellular adhesion molecules, which support the physical attachment of cells.
[18] Hydrogel alginates have emerged as one of the most commonly used materials in organ printing research, as they are highly customizable, and can be fine-tuned to simulate certain mechanical and biological properties characteristic of natural tissue.
The ability of hydrogels to be tailored to specific needs allows them to be used as an adaptable scaffold material, that are suited for a variety of tissue or organ structures and physiological conditions.
[19] A major challenge in the use of alginate is its stability and slow degradation, which makes it difficult for the artificial gel scaffolding to be broken down and replaced with the implanted cells' own extracellular matrix.
[20] Alginate hydrogel that is suitable for extrusion printing is also often less structurally and mechanically sound; however, this issue can be mediated by the incorporation of other biopolymers, such as nanocellulose, to provide greater stability.
Current synthetic polymers with excellent 3D printability and in vivo tissue compatibility, include polyethylene glycol (PEG), poly(lactic-glycolic acid) (PLGA), and polyurethane (PU).
[21] Due to high vascular and neural network construction, this material can be applied to organ printing in a variety of complex ways, such as the brain, heart, lung, and kidney.
HA combined with synthetic polymers aid in obtaining more stable structures with high cell viability and limited loss in mechanical properties after printing.
Lastly, a series of biodegradable polyurethane (PU)-gelatin hybrid polymers with tunable mechanical properties and efficient degradation rates have been implemented in organ printing.
These model organs provide advancement for improving surgical techniques, training inexperienced surgeons, and moving towards patient-specific treatments.
[28] 3D organ printing technology permits the fabrication of high degrees of complexity with great reproducibility, in a fast and cost-effective manner.
[3] 3D printing has been used in pharmaceutical research and fabrication, providing a transformative system allowing precise control of droplet size and dose, personalized medicine, and the production of complex drug-release profiles.
[1] This act was set in place to ensure equal and honest distribution, although it has been proven insufficient due to the large demand for organ transplants.
Studies have characterized printed organs as multi-functional combination products, meaning they fall between the biologics and devices sectors of the FDA; this leads to more extensive processes for review and approval.
[33] Currently, the 3D printers, rather than the finished products, are the main focus in safety and efficacy evaluations in order to standardize the technology for personalized treatment approaches.
Organ printing can decrease or eliminate animal studies and trials, but also raises questions on the ethical implications of autologous and allogenic sources.
Altogether, organ printing possesses short- and long-term legal and ethical consequences that need to be considered before mainstream production can be feasible.
[38] In addition, the ability to print models of human organs to test the safety and efficacy of new drugs further reduces the necessity for animal trials.
[40] The company Organovo, which designed one of the initial commercial bioprinters in 2009, has displayed that biodegradable 3D tissue models can be used to research and develop new drugs, including those to treat cancer.
[42] The challenges faced in the organ printing field extends beyond the research and development of techniques to solve the issues of multivascularization and difficult geometries.
