Researchers at Monash University in Melbourne, Australia, have achieved a significant breakthrough in the field of biomedical engineering. They have successfully 3D-printed living neural networks using rat brain cells, opening up new possibilities for drug testing and the study of brain function. This cutting-edge technology has the potential to replace traditional animal testing methods and usher in a new era of personalized medicine.
3D-printed mini-brains: A viable alternative to animal testing
At the beginning of 2023, the U.S. Congress passed legislation urging scientists to reduce their reliance on animals in federally funded research. This move was prompted by the signing of the U.S. Food and Drug Administration’s Modernization Act 2.0, which allowed for the exploration of high-tech alternatives in drug safety trials. One of the most promising alternatives is the use of 3D-printed mini-brains.
These mini-brains could potentially replace the need for testing new drugs on thousands of animals. The researchers at Monash University have taken a significant step in this direction by 3D-printing living neural networks composed of rat brain cells. This innovative approach holds the promise of more ethical and effective drug trials.
To create these 3D-printed neural networks, the Monash University team utilized a unique method. They squeezed “bioink” โ a mixture of rat brain cells suspended in a gel โ through a nozzle and into a scaffold, similar to how inkjet printers apply ink to paper. The neural structures were built layer by layer, with eight vertical layers alternated between bioinks with and without cells.
This approach allowed for the precise control of cell placement on top of recording electrodes while maintaining a 3D structure that mimics the complexity of normal brain tissue. The neural networks not only contained neurons but also astrocytes, oligodendrocytes, and microglia, crucial support cells for neuron health and connectivity.
The success of the 3D-printed neural networks lies in their functionality. These networks exhibited behavior similar to that of real neurons, including the extension of long axons to communicate across layers. The electrical activity of the cells was recorded using microelectrodes, and their chemical communication was visualized using a fluorescent dye.
This functional mimicry of real neural networks is crucial for potential biomedical applications, such as drug discovery and studying neurodegenerative diseases. For these applications, the neural networks must closely replicate the behavior of actual brain cells.
Challenges and future directions
While this breakthrough is promising, there are still challenges to overcome. One critical challenge is scaling up the technology. The 3D-printed neural networks created in the Monash experiment contained a few thousand neurons per square millimeter, while the human brain has billions of neurons. Scaling up the precise but slow 3D-printing process for commercial drug testing and large-scale research will require further development.
Additionally, ensuring the survival and functionality of human cells in 3D-printed neural networks is an ongoing challenge. Researchers must find ways to create gels that mimic the brain’s properties while allowing for 3D printing without harming the cells.
Despite these challenges, the potential benefits of 3D-printed living neural networks are immense. The technology has the potential to reduce the need for animal testing in various research settings. However, scientists may need time to embrace this innovative approach, as established methods and practices are deeply ingrained in the research community.
The future of personalized medicine also holds great promise. Hospitals could potentially host 3D-printing suites, where clinicians use patient biopsies to print tissues for drug testing, providing tailored treatments for individuals.
