Background
Friends had Central Perk cafe, the gang from How I Met Your Mother had MacLaren’s Pub and we have Charlie’s Pizza joint. What started as a trivial discussion about printing human organs over a stone-baked Margherita quickly evolved into us applying for a bid to participate in the BioMaker Challenge, with the objective of Developing an open & affordable 3D bioprinter.
The beginnings of 3D printing date back to the 1980’s, when it was commonly known as its more mouthful synonym stereolithography (SLA), a technology pioneered by Charles W. Hull. Revolutionized with SLA, one could translate a 3D design from a data file into a physical object, in a relatively short time. The household notion of 3D printing is testament to the success of SLA, which originated from the company 3D Systems Corporation.
Fast forward 40 years, my neighbours are at home 3D printing little elves for their garden, my cousin is buying a 2-story building printed by an enormous SLA machine, my doctor is offering his patients custom 3D printed ear implants, heart valves or bones - SLA has already infiltrated many aspects of our lives, economy and medical care. Much of this progress came about because of the RepRap project, whose aim was to create an open-source 3D printer capable of printing most of the parts needed to replicate itself, making it cheap enough for hobbyists. Today’s consumer 3D printer companies, and the widespread use of 3D printing, grew out of the RepRap hobbyist community.
The field of regenerative medicine could hugely benefit from 3D printing techniques to offer personalized medicine to its patients, by for example printing organs made of one’s own cells. However, these applications are challenged by the complex architecture of human organs, the difficulties of supporting living cells, introducing foreign materials in a human body and working at a microscale.
Addressing these issues, companies and academic researchers have built 3D printing platforms, specialized for biological materials, hence 3D bioprinting. Not surprisingly, these come at a prohibitive cost, up to £200K for the printer only.
BioMaker Challenge
During our weekly pizza gatherings we talked about how it would be great to have an open-source bioprinting project, along the same lines as the original RepRap project. It could make the technology more accessible and bring printing human organs for transplantation a step closer. None of our backgrounds were in bioprinting, but our combined skillsets did range from engineering and programming to cell biology, with diverse backgrounds in start-ups, industry and academia. The Biomaker challenge would be a great way to work together on a project where we could contribute something to the 3D printing community, and learn a lot along the way. Plus it would be fun!
Bertie the 3D bioprinter.
So as part of the BioMaker Challenge, we set out to address the lack of reasonably priced open-source 3D bioprinters in the market by Developing an open & affordable 3D bioprinter. With this project still in its infancy, working with human cells was out of the scope due to ethical and practical reasons. Nevertheless, we attempted to design our 3D printer to potentially print corals, an application with a shorter timeline, more amenable to working in the absence of a biological laboratory and with direct benefits to a problem close to our hearts, the depreciation of the ocean’s corals. Our project branched into two components outlined below:
1. Converting an existing open-source 3D printer into a 3D bioprinter capable of extruding biomaterial.
Our inspiration to address this first problem is drawn from a paper by an American group (Push et., 2018), in which they describe the design of a syringe pump large volume extruder (LVE) of low cost, compatible with printing biomaterial. This involves the purchase of standard materials (e.g: 60mL syringe, bolt nuts) and the 3D printing of other assembly components with a PLA extruder from a standard 3D printer. The newly assembled LVE would then replace the printer’s standard PLA extruder and allow the printing of biomaterials.
With this in mind, many hours of research and discussions went into selecting the right 3D printer as a foundation for our bioprinter - we were certain about two things: it had to be open-sourced and stay within a reasonable budget. We finally settled on the RepRap Ender 5 3D-printer. In addition to the syringe extruder, we were interested in trying to integrate a peristaltic pump in our system because it would allow us to extrude multiple bio-inks at once.
Adding a valving architecture between the reservoirs and the pump enables the switching of the reservoir that bioinks are aspirated from on the go, thereby enabling the interlinking of multiple inks of different cell types in 3D space.
After a few months of putting all the hardware together and with a sprinkle of software, Bertie the Bioprinter was born!
2. Developing a bioink suitable for sustaining living cells.
Regardless of the organism in question, a bioink should:
a) Contain the right nutritional environment for specialized cells.
b) Maintain a single-cell suspension (prevent cells from clumping together and/or from dying from being separated from their friends).
c) Provide a physical scaffold once printed to keep the shape of the 3D model.
d) Use materials that are safe to insert in the receiving environment.
Printing human cells was out of the scope of Biomaker, so we initially turned our attention to another challenging bioprinting application, trying to 3D print coral (which not all of us knew was a living organism!). Coral numbers and health have declined rapidly as a result of environmental conditions and their slow growth cycle. If coral could be 3D bioprinted, perhaps it could be transplanted back into reefs to bring them back to life.
We dove into the scientific literature and identified two such bioink formulas, which are, in theory, capable of supporting the life cycle of corals and providing an “ocean-friendly” physical scaffold. It turned out however that coral species are high maintenance, requiring expensive aquariums and daily care. Even the most experienced coral growers find it challenging to maintain a community of the families of coral that were the right size to fit our bioprinter. We realised that we didn’t have the funds or the time to manage coral during the Biomaker Project, but we did make connections with coral researchers who we hope to work with on this project in the longer term.
Printed phytoplankton using Bertha the bioprinter.
We were however determined to evaluate the efficacy of our bioinks, and didn’t let coral’s needy demands deter us. One of the bioinks we identified is based on the chemical interaction of sodium alginate and calcium chloride, which create a solidified gel upon contact. At the concentration used, these chemicals didn’t affect the survival of phytoplankton, a single cell organism we chose to work with for its relative low cost, ease of maintenance and ability to survive as single cells.
By the end of the project we were able to print a very slimy collection of phytoplankton, and affectionately named it Bertha. Bertha still sits in someone’s fridge for posterity.
Future
The BioMaker Challenge was an incredible opportunity for us to concretise an idea and start along the path to our long term goal. We also got to meet a wonderful community of makers and with their help and feedback we hope to further refine Bertie the Bioprinter. Moving forward, we plan to improve Bertie’s performance in terms of printing precision and its ability to run complex modes (e.g: multiple bioinks printing at once), as well as make him suitable for sterile work (e.g: ventilation, UV lights). We also plan to develop application specific bioinks for Bertie to print.
We’d like to take this opportunity to thank the BioMaker Organisers (special thanks to Alexandra, Jenny & Jim) for arranging this event, Professor Ludovic Vallier (Cambridge Stem Cell Institute, Jeffrey Cheah Biomedical Centre) for supporting our ideas and administrative needs as well as the BioMakeSpace Cambridge who welcomed us in their community. Thanks to the BioMaker Challenge, we are now one small step closer to 3D printing organs, and in the meantime, Bertie is on standby for printing COVID-19 related materials (with the original PLA extruder) if need be.
Julie, Sebastian, Monica, Robin, Ben & Tejas
PS, For more details of the project, check out our Hackster :-)