Elephant trunks and garden hoses hardly look like inspirations for a miniature 3D bioprinter.
Yet they’ve led scientists at McGill University to engineer the smallest reported bioprinting head so far. Described within the journal Devices, the device has a versatile tip just 2.7 millimeters in diameter—roughly the length of a sesame seed.
Bioprinters can deposit a big selection of healing materials directly at the positioning of injury. Some bioinks combat infections in lab studies; others deliver chemotherapy to cancerous sites, which could prevent tumors from recurring. On the operating table, biocompatible hydrogels injected during surgery help heal wounds.
The devices are promising but most are relatively bulky. They struggle to achieve all of the body’s nooks and crannies—including, for instance, the vocal cords.
It’s easy to take our ability to talk without any consideration and only appreciate its loss after catching a foul cold. But as much as nine percent of individuals develop vocal-cord disorders of their lifetimes. Smoking, acid reflux disorder, and chronic coughing tear at the fragile folds of tissue. Abnormal growths and cancers also contribute. These are often removed with surgery that comes with a major risk of scarring.
Hydrogels may help with healing. But because throat and vocal cord tissue is so intricate, current treatments inject it through the skin, relatively than precisely into damaged regions.
But the brand new device can, in theory, sneak right into a patient’s throat during surgery. Its tiny printhead doesn’t block a surgeon’s view, allowing near real-time printing after the removal of damaged tissues.
“I assumed this is able to not be feasible at first—it gave the impression of an not possible challenge to make a versatile robot lower than 3 mm in size,” Luc Mongeau, who led the study, said in a press release.
Although only a prototype, the device could someday help restore people’s voices after surgery and improve quality of life. It also may lead to the delivery of bioinks containing medications and even living cells to other tissues through the nose, mouth, or a small surgical cut.
Squishy Band-Aid
Surgery inevitably ends in scars. While these are an annoyance on the skin, excessive scarring—called fibrosis—seriously limits how well tissues can do their jobs.
Fibrosis in lungs after surgery, for instance, results in infections, blood clots, and a general decline in normal respiration. Scarring of the center tampers with its electrical signals and sometimes results in irregular heartbeats. And for delicate tissues like vocal cords, fibrosis causes lasting stiffness, making it difficult to intonate, sing, or talk like before—essentially robbing the person of their voice.
Scientists have found a spread of molecules that might aid the healing process. Hydrogels are one promising candidate. Soft, flexible, and biocompatible, hydrogel injections provide a squishy but structured architecture supporting vocal cords. Studies also suggest hydrogels boost the expansion the healthy tissues and reduce fibrosis.
But because vocal cords are difficult to focus on, injections are handled through the skin, making it difficult to regulate where the hydrogel goes.
Another is to 3D print hydrogels directly within the body and repair damage during surgery. Each handheld and robotic systems have been successfully tested in labs, and minimally invasive versions are on the rise. One design uses air pressure to bioprint hydrogels contained in the intestines. One other taps into magnets to repair the liver. But existing devices are too large to accommodate vocal cords.
Surgical Trunks
To heal vocal cords, a perfect mini 3D bioprinter must seamlessly integrate into throat surgeries. Here, surgeons insert a microscope through the mouth and suspend it contained in the throat. While it sounds uncomfortable, the procedure is extremely efficient with little pain afterward.
The printhead must snake across the microscope but additionally flexibly adjust its position to focus on injured sites without blocking the surgeon’s view. Finally, the speed and force of the hydrogel spray needs to be controllable—avoiding the equivalent of by chance squeezing out an excessive amount of superglue.
The brand new bioprinter’s has a printhead a bit like an elephant’s trunk. It has a versatile arm that easily slips into the throat with a 2.7-millimeter arched nozzle at the tip. Picture it as a fine-point Sharpie connected to a versatile tube. Three cables operate the printhead and control nozzle movement by applying tension, like strings on a puppet.
The system’s brain is within the actuator housing, which looks like a tiny plastic gift box. It holds a syringe of hydrogel for the printhead and pilots the adjustable cables using motors that precisely move the printhead to its intended location with a custom algorithm. Other electronics allow the team to regulate the setup using a wireless gaming controller in real time.
The actuator will be mounted under a regular throat surgery microscope so it’s out of the best way during an operation, wrote the team.
To place the device through its paces, the team used the mini bioprinter to attract a spread of shapes, including a square, heart, spiral, and various letters on a flat surface. The printhead accurately deposited thin lines of hydrogel, which will be stacked to form thicker lines—like repeatedly tracing drawings using a fine-tipped pen.
The team also tried it out in a mock vocal cord surgery. The “patient” was an accurate 3D model of an individual’s throat but with various kinds of wounds to its vocal cords, including one which completely lacked half of the tissue. The bioprinter successfully made the repairs and reconstructed the missing vocal cord without issue.
“A part of what makes this device so impressive is that it behaves predictably, although it’s essentially a garden hose—and when you’ve ever seen a garden hose, you already know that while you start running water through it, it goes crazy,” said study writer Audrey Sedal.
The flexibleness comes at a value. Though the printhead design deforms to forestall injury to tissues, this also means it’s more susceptible to mechanical vibrations from the actuator’s motors, which dings its accuracy.
As of now the mini printer requires manual control, however the team is working on a semi-autonomous version. More importantly, it must be pitted against standard hydrogel injection methods in living animals to point out it’s secure and effective.
“The subsequent step is testing these hydrogels in animals, and hopefully that may lead us to clinical trials in humans to check the accuracy, usability, and clinical outcomes of the bioprinter and hydrogel,” said Mongeau.