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3D printing in medicine is one of the greatest promises of modern science.

February 21, 2019

This is a completely new look at transplantology.

Need for artificial organs

The times in which we live today are characterized by very dynamic technological progress. Modern engineering is no longer based solely on mechanics and electronics. Thanks to the rapid development of biomedical sciences, engineering and medicine came together; this is how biomedical engineering, and especially tissue engineering, came into being.  The development of medicine so far has resulted in a significant extension of human life. For the last half a century the life of an average Pole has been extended by almost 9 years – therefore our organs must last much longer for us. Certainly, many factors have contributed to this situation, such as the widespread use of antibiotics or much better survival rates among small children, thanks to widespread vaccination. Unfortunately, not all diseases can be prevented by vaccination or pharmacological treatment. In some cases, a skin, bone marrow and whole organs transplantation is required. An example of one such disease is diabetes, the treatment of which is mainly based on insulin, and in more advanced stages such as kidney failure, visual impairment or lack of feeling of low glycemia, transplantation is needed. One of the three variants is used, namely pancreatic transplantation, pancreas with kidney or the pancreatic islets themselves. However, waiting for a transplant may take many years. This is mainly due to the limited number of donors. In the case of many organs, they can only be obtained from deceased donors. Once the recipient has a transplant of his or her dreams, there is a risk that his or her body will not accept the transplanted organ. Unfortunately, the body’s defensive reactions often lead to the rejection of the organ. In addition, the recipient must take immunosuppressive drugs for the rest of his or her life, i. e. drugs that prevent rejection.

What if it would be possible to create an organ from cells taken from the patient? Wouldn’t that be an ideal solution? Create a new, personalized organ with almost nothing? Is this possible?

Through the searching for answers to these questions, a new branch of science has developed – tissue engineering, which deals with the development of methods of creating various artificial creations, fulfilling the functions of their own organs, which in the future will be able to be implanted in patients.

Let’s make spare parts for people – the development of tissue engineering

Tissue engineering is a science on the borderline between medicine and materials engineering. The first steps in this field were made to look for materials that would have the right properties for medical use – they would be durable and would not harm the body. Research in this field was conducted on the basis of various groups of substances, among which metals, such as surgical titanium, aroused particular interest at first. Implantology and reconstruction surgery have long been based on the achievements of tissue engineering. Currently, not only biocompatible but also biodegradable materials are being developed. They are designed to enable the regeneration of damaged body tissue by performing the function of “scaffolding” for differentiating cells. Furthermore, a characteristic feature of these materials is the easy and relatively fast degradation of the implant produced from them within the body. The products of such decomposition, such as water or carbon dioxide, are neutral for the body compounds . But how to create such implants?

Tissue engineering uses many methods to create a functional implant. Currently, 3D bioprinters are commonly used. They allow not only to print an artificial creation with the use of appropriate components, but ultimately they are also to be used to create a fully functional organ.

How it works – bioprinting at a glance

The first work on bioprinting in the early 21st century used ordinary inkjet printers using piezoelectric effect to create ink droplets – it does not require high temperatures, so they could be used to print inks together with live cells. Currently, the most commonly used form of bioprinting is extrusion – with the help of a computer, a bioink is squeezed out of the cartridge (syringe) with cells, which are placed in successive layers creating a three-dimensional structure. Printing is controlled from the computer and the printer will lay out the layers as we order it. During printing we can control physical and chemical conditions such as: temperature, pressure, pH value, which is an important element that allows to influence the consistency of bioink after printing – that is, the change from liquid to solid. An important limitation at the moment is the relatively low resolution of about 100 μm for printers using tissue material. In addition, stacking layers and creating vessels is still a challenge for 3D printing. When 20-30 layers are superimposed on top of each other, the lower layers begin to squeeze like a few cakes on top of each other. At the moment, only printing in a weightless state would solve this problem.

One of the biggest problems with 3D bio printing is to create the right bio ink, a kind of gel that will create an environment suitable for cell growth.

When we have finished the bio ink and designed the model of our design, we can start printing, which is certainly not as simple as it seems. There are several methods of bioprinting, as I mentioned earlier.The main differences between them are the possibilities of using bio-inks with appropriate physicochemical properties, and thus – the possibility of accurate representation of the 3D model created.

What has been printed – are we approaching the reception of properly functioning organs?

Many research teams from all over the world have already achieved their first successes in the field of organ and tissue bioprinting. These mainly consist of printing bioskeletons on which cells of different origins were cultured. At present, bones and cartilage are being printed, and a mussel or bladder have also been printed. Creating elements of the body that are not bleeding is no longer as challenging as it was a few years ago. However, work on obtaining a fully functional organ also requires the development of a system of blood vessels through which this organ can be fed.

Currently, work on the bionic liver, kidney, pancreas and even the heart is still in progress. Moreover, it seems that 3D tissue printing will be helpful not only in transplantology, but also in pharmacology in order to personalize medicine or toxicology to study the effects of substances not only on cell cultures, but on entire living tissues/organs. The possibility of using printed tissues from patient’s cells, which will be subjected to pharmacological tests “in vitro” will enable a better and more appropriate chronic therapy.

Author of article: Michał Wszoła MD, PhD

The article was written in cooperation with Rzeczpospolita, as part of the series Oswoić Naukę – To Tame Science. This is the first of twelve articles bringing the world of science closer. The articles will appear in the newspaper once a month.