By Cristina Riquelme Vano
Over 120,000 people in the US are on a waiting list for organs, and many others experience the long-term damaging effects of post-transplant immunosuppression (National Kidney Foundation, 2020).The growing need for an alternative procedure to organ replacement has brought together a multidisciplinary team of researchers and bioengineers to develop a promising new approach, 3D bioprinting.
3D bioprinting is an emerging technique used to create living tissues such as skin, blood vessels and bones via 3D printing; It is a technique that many scientists in the field believe will revolutionise the healthcare system in the coming decades.
3D printing produces three dimensional objects from a previous design using a layering process. For example, to make a plastic glass in 3D printing, the plastic (the “ink”) is liquefied and the 3D printer adds layer after layer of plastics until the plastic glass design is completely formed. 3D bioprinting is slightly more challenging since its material source, it’s “ink”, is living cells (Wyss Institute, 2020).
Firstly, 3D bioprinting starts with a model of a structure (e.g an organ), which will be recreated layer-by-layer out of a bioink, the living cells. This model typically comes from a computer-generated design program or a downloaded file from the internet. This model file is then fed into a slicer which analyses the geometry of the model and generates a series of thin layers, called slices. Finally, the slices are transformed into the path data (stored as a g-code file) which can be sent to the 3D bioprinter for printing, following the instructions in the g-code file. These instructions include variations in temperature, pressure, crosslinking intensity, frequency and most importantly, the 3D movement path generated by the slicer (Allevi, 2020).
Needless to say, this bioink must fulfill certain conditions, namely – nutrient content, water availability and optimal oxygen levels in order for living cells to stay alive. This environment is achieved using a microgel, which can be described as a kind of gelatin with life-sustaining compounds like vitamins, proteins and essential ions such as calcium and magnesium. Additionally, to enhance the cell growth of the living cells, the cells themselves are planted in 3D scaffolds made of collagen, so they can grow into a fully functional tissue (Wyss institute, 2020).
These principles can be outlined through the process of 3D bioprinting a bladder. Firstly, the patient’s bladder is scanned to determine the size and shape needed for a replacement, and then a 3D collagen scaffold is created for efficient cell growth, adding the cells from the patient to this scaffold. The bioreactor then creates the optimal environment conditions for the cells to grow into a bladder, following the precise structure controlled by the bioprinter.
This process can take as long as 8 weeks and is very labour-intensive, but promises amazing results such as bioprinting synthetic screens or a cornea. It is due to these results that 3D bioprinting now poses itself as the solution to critical tissue shortages endangering many lives; according to NHS statsitics, 429 patients died in 2014 in the UK while on the active waiting list for an organ transplant (Knapton, 2020). Additionally, 3D bioprinting offers a means of testing drugs faster, decreasing costs, and being more experimentally viable in comparison to animal testing, since testing medication on mice, rabbits or other animals is in many cases inefficient as the drug could still have differing effects on humans.
3D bioprinting is still in its infancy, and its observed potential is spurring rapid development in the field. Although it is currently a time-consuming process, it is predicted to become much more efficient – at an estimated process time of a few days. As Dr. Atala explained: “Your surgeon will ship your tissue sample to a company. A few days later, the organ will arrive on a sterile container via FedEx, ready for implantation.” The current pioneers of bioprinting are Organovo and CELLINK & Co. Organovo announced in 2014 that a successful printing of liver tissue had managed to function as a real liver for weeks. They have also developed fully functional human kidney tubular tissues as well as synthetic skin. CELLINK & Co is focused on 3D cell culture and enhanced therapeutics, amongst other branches of bioprinting applications.
In conclusion, 3D bioprinting offers scientists and doctors a great advantage to better target treatments and improve patients’ outcomes. However, it already has some challenges. Namely, the vast expenses of this technology coupled with the threats of the black market of printed organs. Nevertheless, once regulations for 3D bioprinters are developed, there remains great potential to grow the 3D bioprinting market and make organ shortages a thing of the past.
National Kidney Foundation. 2020. Organ Donation And Transplantation Statistics. [online] Available at: <https://www.kidney.org/news/newsroom/factsheets/Organ-Donation-and-Transplantation-Stats> [Accessed 26 August 2020].
Wyss Institute. 2020. 3D Bioprinting Of Living Tissues. [online] Available at: <https://wyss.harvard.edu/technology/3d-bioprinting/> [Accessed 26 August 2020].
Allevi. 2020. What Is 3D Bioprinting? | Bioprinting Explained – Allevi. [online] Available at: <https://www.allevi3d.com/what-is-3d-bioprinting/> [Accessed 26 August 2020].Knapton, S., 2020. Organ Donation Crisis Threatens Hundreds Of Lives. [online] Telegraph.co.uk. Available at: <https://www.telegraph.co.uk/news/health/news/11749503/Organ-donation-crisis-threatens-hundreds-of-lives.html> [Accessed 26 August 2020].