This time I want to tell you about a branch of 3D printing that stands separately from other branches and is absolutely amazing, already allowing us to 3D print live functional tissue and whole, if simple, organs. It’s called bioprinting. Of course, there are other uses for 3D printing in medicine than printing organs and tissue, and I’ll be mentioning those as well. Let’s get started!
Printing live tissue and organs: how it works
It is hard to believe at first that even with the current technologies and resolutions one can possibly print something as complex as human tissue, let alone a live and functioning organ. How is it done?
The answer is very simple, as everything genius is… well, simple from a practical standpoint. Amazingly, nature comes into play and does most of the job.
So how do bioprinters look like? If anything, they are even simpler than most of the other 3D printers out there, at least in concept. Above you can see the picture of one of the possible concepts of a bioprinter. The one depicted on the picture has almost printed a human heart, and soon it will be ready for transplantation. This bioprinting machine looks and functions similar to a simple inkjet printer that prints by spraying ink from the nozzles so as to form the desired pattern (text or a picture). In fact, some researchers and pioneers of bioprinting are using inkjet printers reconfigured for the task of printing live tissue. Instead of spraying ink on paper, such a bioprinters spray solution of live cells that are to form the printed tissue along with a support structure, usually a gel-like substance that helps the future organ maintain its shape while it is still “liquid”. The solution and the support substance are quite often called bioink and biopaper respectively, exploiting the obvious analogy between inkjet printers and bioprinting machines.
But how can this work? What will we achieve by simply making a 3D structure of droplets of live cells solution? Any live tissue is so complex in its structure, let alone an entire functioning organ… Here is where nature takes over. Gradually, the droplets merge, forming the desired shape, and then the cells start arranging and aligning themselves following the genetic programs coded in each of them, thus creating a functional live tissue that has a shape predefined by the process of printing. Lastly, the biopaper gets dissolved away or otherwise removed, leaving a final bioprinted organ or tissue.
Each drop of the sprayed solution can contain a large number of cells. For instance, Organovo’s NovoGen MMX bioprinter lays down bioink spheroids, containing tens of thousands of cells each. The picture below provides a good illustration of bioprinting process: after bioink droplets have been printed into a layer of biopaper gel, another layer of biopaper is applied and the process begins anew, building the future organ from the bottom up, after which it is left to itself to “mature”.
Furthermore, bioink can contain cells of different types and once the printing is done, they sort themselves out according to their functions. For instance, experimental blood vessels have been printed with bioink spheroids containing a mix of endothelial, fibroblast and smooth muscle cells. Once placed where needed by the bioprinter, and with no intervention or help from outside, the endothelial cells migrate to the inside part of the printed blood vessel, the smooth muscle cells occupy the middle layer, while the fibroblasts move to the outside.
As Organovo has clearly demonstrated using their bioink printing technology, it is not necessary to print out the future organ in every minute detail with a bioprinter, as once the needed cells are placed in roughly the right place, nature takes over and completes the job.
It is important to note that it is not necessary to use a 3D printer to create an organ. 3D printers only place the cells where they are supposed to be, and the more complex the geometry, the more useful they are. However, it is also possible to use other ways of making the cells assume the desired shape. For instance, one can create a sort of scaffold of dissolvable material and drench it with cell solution, or create a special mold. Then again, such a mold or a scaffold can be printed out on a 3D printer with a special dissolvable material and then coated with live cells.
Even sugar can be used for printing out a scaffold, as in this video:
Specialists from Organovo believe that the kidney will be the first organ to become widely available for printing and transplanting. This is because kidney is quite straight-forward in functional terms. Indeed, a printed kidney doesn’t even have to look just like a natural one, so long as it is capable of cleaning waste products out of the blood. Some people already speculate that being able to print new organs such as liver in the future will make people less attentive to their health and encourage various unhealthy habits such as drinking alcohol in large quantities.
It will be some time before everyone will be able to go and order, say, a new heart to be 3D printed for transplantation, perhaps several decades, but scientists and doctors look forward to that future, as the ability to print new organs on demand will enable them to save numerous lives and solve so many problems. For instance, that of rejection. When an organ is taken from a donor, quite often it is rejected by the patient’s organism after transplantation: the organism recognizes it as something foreign and fights it rather than heal itself. With 3D printed organs there will be no such issue, because they will be printed from the patient’s own cells, taken from him and multiplied in a special environment.
Also, the problem of waiting for a donor will be solved. There are much more people who are in need of, say, heart transplantation, than there are donors, and so patients have to wait for a very long time, which is not a good thing when your own heart is failing.
Printing tissue samples for drug tests
Fascinating as the idea of printing organs for transplantation might be, its time hasn’t yet come. However, bioprinting is already being extensively used for another very important purpose, that of testing various new drugs.
The thing is, for a new drug to be developed and released it must prove its efficacy, and most, in fact, almost all of the candidates for a new drug tested on earlier stages don’t pass all the tests. The standards are high and the work is quite tedious. Conventional way was to test a candidate for a new drug on some cells in a Petri dish, after which (in case of success) there is trial on animals and then, finally, trials on humans. Very few substances pass all the necessary tests and it helps greatly when instead of cells in a dish drugs are tried on a 3D printed tissue sample, which behaves more like a part of a body than cells in a dish, because cells in a Petri dish don’t behave the way they do in a 3-dimensional architecture of the body. So when scientists in a lab have to pick one among many drugs to be taken for the next trials, using 3D printed tissue samples allows them to make this choice more reliably, with more chance for success, which means faster, safer and more cost-efficient drug developing process.
In situ bioprinting
We can 3D print organs and transplant them into the patient’s body, we can print small patches of tissue and use them to patch the patient up, but it is also possible to print directly on a body, or even inside a body. It is quite possible that in the nearest future doctors will 3D scan the wound or a burn and spray layers of cells atop it, making it heal very rapidly.
Pioneers of bioprinting
Although bioprinting hasn’t yet kicked off, people have been making and testing experimental bioprinters for quite a long time. For instance, in 2002 Professor Makoto Nakamura realized that the size of the droplets of ink being sprayed by a standard inkjet printer is about the size of a human cell. Therefore he decided to use the same technology and by 2008 he had created a functioning bioprinter that could print out biotubes similar to blood vessels. Professor Nakamura hopes that one day he’ll be able to print entire organs for transplantation. The video below demonstrates his bioprinter in the process of fabrication of a section of a biotube in real time.
Other ways 3D printing can and does make itself extremely useful in medicine
There are multiple ways 3D printers can be of great help in medicine. For example, when complex and difficult surgery is needed, sometimes a 3D model of the part of the patient’s body to be operated is printed out so that the surgeons can train on this model before proceeding to the real thing.
Also, quite often, it is convenient to use 3D printing for printing out custom prosthetic appliances or for printing molds for casting them in metal.
Practice Surgical Procedures on 3D Printed Bone:
Thank you for reading this article! If you have any questions, suggestions or comments, let me know in the comments section.