A small array of microelectrodes beneath the cells recorded electrical activity in the gel surrounding the cells, while other electrodes directly stimulated neurons and recorded their responses. By using fluorescent dyes to visualize the movement of calcium ions under a microscope, the researchers were able to see how cells communicate chemically. “They did exactly what we expected,” Forsyth says. “There were no surprises.”
Although it may not be surprising that these neurons behave in the following way, neuron, that’s a big deal. When it comes to potential biomedical applications such as drug discovery and neurodegenerative disease research, the value of neural networks is determined by their functionality.
It starts with not killing cells when printing. When standard 3D printers use plastic filament, they melt the plastic to make it moldable and heat it to temperatures well above the temperature of the human body. These are cells that are ineligible for neurons, extremely finicky cells that can only survive in carefully tailored gels that closely mimic the squishy, body-temperature properties of the brain. “It’s really difficult to make a gel that’s as soft as the brain but can be printed with a 3D printer,” Moore says.
“It’s important not to kill the cells. But in the case of neurons, it’s very important not to kill the electrical activity,” said Stephanie Willers, a biomedical engineering professor at the University of Victoria in Canada who was not involved in the study. added. Previous versions of 3D printed neural tissue often excluded glial cells, which help maintain a comfortable environment for sensitive neighboring neurons. Without these, “neurons still have some electrical activity, but they can’t fully replicate what we see in the body,” she says.
Willers thinks the new experiment is promising. Although these neural networks are made in rat cells, “this is a proof of concept that ultimately this could be done in human cells as well,” Willers said. Still, future experiments will need to reproduce this level of functionality in human cells before these neural network models can be used in translational research or medicine.
There’s also the issue of scaling. The tissue printed in Monash’s experiment contained thousands of neurons per square millimeter, equating to hundreds of thousands of cells per 8 x 8 x 0.4 mm structure. However, in the human brain, 16 billion neurons It goes without saying that there are billions more glial cells in the cortex alone.
As Moore points out, 3D printing such delicate tissue is relatively time-consuming, even if the final product is small. Much more work needs to be done to scale this precise but time-consuming technology from academic research institutions to large pharmaceutical companies. At large pharmaceutical companies, companies often test dozens of drugs at once. “It’s not impossible,” Moore said. “It’s just going to be difficult.”axosimThe neurotechnology startup co-founded by Moore has already begun building 3D models of human neurons and peripheral nerves for commercial drug testing. )
The technology has the potential to replace animals in many research settings, from basic neuroscience to commercial drug development, but scientists may be slow to make the switch. . Often, Moore says, scientists like him are “stuck” and reluctant to invest the time, money and effort required to move away from proven animal models. . “It will take time to convince scientists to abandon this approach to engineered tissues,” he says. “But I’m very optimistic that we’ll gradually reduce the number of animal experiments.”
