A team of scientists from the University of California, San Diego has reported a new advancement in 3D bioprinting. For the first time in history, they managed to print an implant that simulates a fragment of the spine. After its installation and engraftment, the rodent regained control over the previously paralyzed hind limbs.
The difficulty in creating implants for the spinal cord is that it is required to connect axons, extremely thin nerve fibers that are sensitive to different conditions. Neither traditional 3D printing materials nor printers are suitable here. The size of one drop of the substance is about 200 microns, while the axons lie in the channels, which are much thinner, therefore, the implant cannot be printed in the usual way, layer by layer.
Scientists have applied the technology of continuous projection microprinting, based on the material polyethylene glycol-gelatin methacrylate. This hydrogel hardens when exposed to ultraviolet radiation, but this happens very quickly, so the liquid polymer was previously mixed with living neural stem cells. Light irradiation is carried out over the entire plane of the material according to the product scheme laid down in the printer, 1000 times faster than conventional 3D printing, after which the output is a solid object with cells embedded in it. It took only 1.6 seconds to print the 2 mm thick implant.
After being installed in the spine of a rat, the implant lasted 4 weeks, and by the 5th it began to degrade - as planned. During this time, the axons managed to grow through the channels in the implant and create stable connections. Now, within a few months, the implant frame will gradually decompose, and living tissues will take its place. If everything goes according to plan, then after clinical trials, in about 5 years, experiments will begin on printing complex parts of the human body.
The first 4 cm human implant model has already been created