Organ printing
Organ printing utilizes techniques similar to conventional 3D printing where a computer model is fed into a printer that lays down successive layers of plastics or wax until a 3D object is produced. In the case of organ printing, the material being used by the printer is a biocompatible plastic. The biocompatible plastic forms a scaffold that acts as the skeleton for the organ that is being printed. As the plastic is being laid down, it is also seeded with human cells from the patient's organ that is being printed for. After printing, the organ is transferred to an incubation chamber to give the cells time to grow. After a sufficient amount of time, the organ is implanted into the patient.
To many researchers the ultimate goal of organ printing is to create organs that can be fully integrated into the human body. Successful organ printing has the potential to impact several industries, notably artificial organs organ transplants, pharmaceutical research, and the training of physicians and surgeons.History
The field of organ printing stemmed from research in the area of stereolithography, the basis for the practice of 3D printing that was invented in 1984. In this early era of 3D printing, it was not possible to create lasting objects because of the material used for the printing process was not durable. 3D printing was instead used as a way to model potential end products that would eventually be made from different materials under more traditional techniques. In the beginning of the 1990s, nanocomposites were developed that allowed 3D printed objects to be more durable, permitting 3D printed objects to be used for more than just models. It was around this time that those in the medical field began considering 3D printing as an avenue for generating artificial organs. By the late 1990s, medical researchers were searching for biocompatible materials that could be used in 3D printing.
The concept of bioprinting was first demonstrated in 1988. At this time, a researcher used a modified HP inkjet printer to deposit cells using cytoscribing technology. 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. The scientists at Wake Forest printed an artificial scaffold for a human bladder and then seeded the scaffold with cells from their patient. Using this method, they were able to grow a functioning organ and ten years after implantation the patient had no serious complications.
After the bladder at Wake Forest, strides were taken towards printing other organs. In 2002, a miniature, fully functional kidney was printed. In 2003, Dr. Thomas Boland from Clemson University patented the use of inkjet printing for cells. This process utilized a modified spotting system for the deposition of cells into organized 3D matrices placed on a substrate. This printer allowed for extensive research into bioprinting and suitable biomaterials. For instance, since these initial findings, the 3D printing of biological structures has been further developed to encompass the production of tissue and organ structures, as opposed to cell matrices. Additionally, more techniques for printing, such as extrusion bioprinting, have been researched and subsequently introduced as a means of production.
In 2004, the field of bioprinting was drastically changed by yet another new bioprinter. This new printer was able to use live human cells without having to build an artificial scaffold first. In 2009, Organovo used this novel technology to create the first commercially available bioprinter. Soon after, Organovo's bioprinter was used to develop a biodegradable blood vessel, the first of its kind, without a cell scaffold.
In the 2010s and beyond, further research has been put forth into producing other organs, such as the liver and heart valves, and tissues, such as a blood-borne network, via 3D printing. In 2019, scientists in Israel made a major breakthrough when they were able to print a rabbit-sized heart with a network of blood vessels that were capable of contracting like natural blood vessels. The printed heart had the correct anatomical structure and function compared to real hearts. This breakthrough represented a real possibility of printing fully functioning human organs. 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 of today, these scientists have been able to develop a functioning prototype. This is a growing field and much research is still being conducted.3D printing techniques
3D printing for the manufacturing of artificial organs has been a major topic of study in biological engineering. As the rapid manufacturing techniques entailed by 3D printing become increasingly efficient, their applicability in artificial organ synthesis has grown more evident. Some of the primary benefits of 3D printing lie in its capability of mass-producing scaffold structures, as well as the high degree of anatomical precision in scaffold products. This allows for the creation of constructs that more effectively resemble the microstructure of a natural organ or tissue structure. Organ printing using 3D printing can be conducted using a variety of techniques, each of which confers specific advantages that can be suited to particular types of organ production.Sacrificial writing into functional tissue (SWIFT)
Sacrificial writing into function tissue is a method of organ printing where living cells are packed tightly to mimic the density that occurs in the human body. While packing, tunnels are carved to mimic blood vessels and oxygen and essential nutrients are delivered via these tunnels. This technique pieces together other methods that only packed cells or created vasculature. SWIFT combines both and is an improvement that brings researchers closer to creating functional artificial organs.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. A 3D structure can then be built in layers using the 2D pattern. Afterwards the bio-ink is removed from the final product. SLA bioprinting allows for the creation of complex shapes and internal structures. The feature resolution for this method is extremely high and the only disadvantage is the scarcity of resins that are biocompatible.Drop-based bioprinting (Inkjet)
Drop-based bioprinting makes cellular developments utilizing droplets of an assigned material, which has oftentimes been combined with a cell line. Cells themselves can also be deposited in this manner with or without polymer. When printing polymer scaffolds using these methods, each drop starts to polymerize upon contact with the substrate surface and merge into a larger structure as droplets start to coalesce. Polymerization can happen through a variety of methods depending on the polymer used. 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. Drop-based bioprinting is commonly utilized due to its productive speed. However, this may make it less appropriate for more complicated organ structures.Extrusion bioprinting
Extrusion bioprinting includes the consistent statement of a specific printing fabric and cell line from an extruder, a sort of portable print head. This tends to be a more controlled and gentler handle for fabric or cell statement, and permits for more noteworthy cell densities to be utilized within the development of 3D tissue or organ structures. In any case, such benefits are set back by the slower printing speeds involved by this procedure. Extrusion bioprinting is coupled with UV light, which photopolymerizes the printed fabric to create a more steady, coordinated construct.Fused deposition modeling
is more common and inexpensive compared to selective laser sintering. This printer uses a printhead that is similar in structure to an inkjet printer; however, ink is not used. Plastic beads are heated at high temperature and released from the printhead as it moves, building the object in thin layers. A variety of plastics can be used with FDM printers. 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. Due to this, these parts have analogous durability, mechanical properties, and stability characteristics. Precision control allows for a consistent release amount and specific location deposition for each layer contributing to the shape. As the heated plastic is deposited from the printhead, it fuses or bonds to the layers below. As each layer cools, they harden and gradually take hold of the solid shape intended to be created as more layers are contributed to the structure.Selective laser sintering
uses powdered material as the substrate for printing new objects. SLS can be used to create metal, plastic, and ceramic objects. This technique uses a laser controlled by a computer as the power source to sinter powdered material. The laser traces a cross-section of the shape of the desired object in the powder, which fuses it together into a solid form. A new layer of powder is then laid down and the process repeats itself, building each layer with every new application of powder, one by one, to form the entirety of the object. One of the advantages of SLS printing is that it requires very little additional tooling, i.e. sanding, once the object is printed. Recent advances in organ printing using SLS include 3D constructs of craniofacial implants as well as scaffolds for cardiac tissue engineering.