3D bioprinting poised to propel medical research forward
3D printing techniques are now being used in medical research to establish more personalized treatment approaches and accelerate drug discovery. This technology unlocks the potential of 3D cell culture approaches to better replicate the human body, gain a better understanding of different cell types, and ultimately develop patient- and organ-specific treatment pathways. This article takes a look at 3D bioprinting – what it is, how it’s done – and explores possible applications and advantages of vegetable bio-inks.
The concept of bioprinting has been around for many years, ever since Robert J. Klebe used a standard desktop inkjet printer to deposit cells by cytoscription. in 1988.1 Fifteen years later, W. Cris Wilson and Thomas Boland of Clemson University pioneered the first inkjet bioprinter – an adaptation of a standard inkjet device – demonstrating its effectiveness by printing fluorescently labeled human cells in culture media.2 The following year, Boland’s team succeeded in creating the first 3D bioprinter by loading cells into a commercial stereolithography printer,3 and interest in the application of 3D bioprinting has grown steadily ever since.
3D bioprinting is essentially a form of additive manufacturing and takes advantage of 3D printing technologies developed for other industries. The main difference is that instead of using solid materials, 3D bioprinters are designed to print liquids or gels – bioinks – and have been adapted to work with living materials. Bioprinters can be inkjet, extrusion-based or laser-assisted systems, and each type of printer has its own advantages in terms of cost, cell viability, cell density and resolution. Compatibility with bio-inks also varies, so it’s important to make sure the bio-printer and bio-ink work well together.
What are bioinks made of?
3D tissue printing is very different from 2D cell printing, requiring a material that can hold cells in different layers. Bio-inks are natural or synthetic biomaterials that can be mixed with living cells and used as a base material to print tissue, organ or bone-like structures. Composed of biological components – to ensure cell viability – and a structural component that retains its rheological properties, they can be cell-laden, scaffold-free or cell-free. Selecting the most appropriate bioink for each application is critical, as ink composition and density can affect cell viability and density. Bio-inks must also be stable and robust, allowing them to be layered without disintegrating.
An expanding market
The development of affordable 3D bioprinters has allowed the technology to become more widely available, and there has been a huge increase in the number of publications citing the use of 3D bioprinting in recent years, as researchers are re-evaluating biology that has traditionally been performed in 2D. Bio-printed 3D cell cultures provide a more biologically relevant representation of the body for in vitro studies versus 2D investigations, leading to the development of disease, tumor and organ models, as well as organ-on-chip applications.
Researchers are also increasingly looking for alternatives to animal models, both voluntarily and in response to tightening regulations. Cellular behaviors and the effects of different drugs can be examined more accurately, while simultaneously reducing the need for animal testing. This is already benefiting areas such as cancer research, where tumor models can be printed to test responses to treatment. Migration assays can also be done to understand how tumor cells move and interact with other cells, and how benign cells become malignant.
In addition, 3D bioprinting opens up possibilities for new patient- and organ-specific treatments, manufacturing personalized medicine more and more a reality. Primary cells can be harvested and used to create patient-specific tumor models, which are then screened against different compounds to see which gives the best response, both for drug discovery and to enable rapid initiation of treatments. tailored. This is a huge and exciting area where bioprinting can have an immediate impact.
Credit: UPM Biomedicals
Bio-inks using plant-based nanofibrillar cellulose hydrogels are proving a popular choice for these applications, mimicking the live environment conducive to cell growth and differentiation. These bio-inks can be used with or without cross-linking agents and diluted to required stiffnesses for a particular application, enabling 3D bioprinting with high precision cell positioning. Unlike animal-derived gels, nanofibrillar cellulose hydrogels are also stable at room temperature and do not suffer from batch-to-batch variations, for improved consistency and ease of use.
From in vitro at live
More recently, scientists have explored the translation of this technology into a clinical setting, to print tissues or organs. Typically, specialized software is used to convert a medical image, such as an MRI or CT scan, into a three-dimensional computer model that acts as instructions for the bioprinter, allowing the generation of a model of the part of the body of interest that could, in theory, be transplanted into a patient. This requires careful selection of the most appropriate and host-compatible biomaterials and printing parameters, allowing responsive living cells to be printed layer by layer and then cultured to generate three-dimensional models that mimic behavior and structures. natural fabrics.
Bio-inks of non-animal origin, such as nanofibrillar cellulose hydrogels, are ideal for this application, as they do not interact with the body to elicit an immune response – a prerequisite for any implant – making the prospect of the impression of human implants more viable. Likewise, there is now evidence that nanofibrillar cellulose hydrogels can be used throughout a complete protocol for the generation of stem cell therapies – from initial cell processing and differentiation, through to their use as cell support for injection – avoiding any matrix problems.4
The way of the future
Today, the top 20 pharmaceutical companies and many major academic institutions use 3D bioprinters. From a drug discovery perspective, 3D bioprinting generates more physiologically relevant models, offering more efficient predictions compared to commonly used animal models, which are increasingly frowned upon and legislated. Better simulation of the body’s response to different compounds means that bad candidates should be eliminated more quickly from the development pipeline, leaving the focus on those with the highest probability of success. This will help accelerate the speed of candidate selection while reducing costs.
The ultimate dream is organ printing – for example, a new pancreas for a diabetic patient – even if it’s still a long way off. 3D bioprinting using the patient’s own cells would reduce the likelihood of rejection and solve the problem of donor shortage. However, implantation should be highly regulated and must be performed in a clinical setting using organs with proof of functionality, printed in a highly sterile environment. Automation has a key role to play here in quality control, and nanofibrillar cellulose hydrogels can contribute to this. These plant-derived materials lend themselves to automation, can be used throughout the cell culture protocol, and can be reliably and reproducibly produced day-to-day, month-to-month, and time-to-time. year to year. Automation also opens the possibility of establishing and validating an end-to-end protocol in one facility and transferring it to another environment, perhaps even another country. This will facilitate approval by relevant regulatory authorities and hopefully allow faster adoption of new therapies.
3D bioprinting has opened the floodgates to 3D cell culture, offering researchers an easy path to better representations of the human body compared to traditional 2D environments. This allows for the study of more complex and sophisticated structures and modes of action, helping researchers better understand cellular behaviors, which can then be applied to the development of new drug therapies and personalized treatment regimens. In the longer term, ‘print it yourself’ organ technology could also become a reality – a truly exciting prospect for researchers, clinicians and patients everywhere.
1. Klebe RJ. Cytoscription: method of cell micropositioning and construction of two- and three-dimensional synthetic tissues. Exp Cell Res. 1988;179(2):362-73. doi: 10.1016/0014-4827(88)90275-3
2. Wilson Jr. WC, Boland T. Cell and organ printing 1: protein and cell printers. Anat Rec A Discov Mol Cell Evol Biol. 2003;272(2):491-496. doi:10.1002/ar.a.10057
Dhariwala B, Hunt E, Boland T. Rapid prototyping of tissue-engineered constructs, using light-curing hydrogels and stereolithography. Tissue Eng. 2004;10(9-10):1316-1322. doi:10.1089/ten.2004.10.1316
4. Chang HT, Heuer RA, Oleksijew AM, Coots KS, Roque CB, Nella KT, McGuire TL, Matsuokaa AJ. A three-dimensional stem cell niche designed in the inner ear by applying a nanofibrillar cellulose hydrogel with a sustained-release neurotrophic factor delivery system. Acta Biomater. 2020;108:111-127. do I: 10.1016/j.actbio.2020.03.007
About the authors:
Johana Kuncova-Kallio is Director, UPM Biomedicals.
Erik Gatenholm is CEO, BICO.
Avijit Minocha is Head of Marketing, BICO.