Stomach ulcers and other gastrointestinal sores affect one out of every eight persons globally, yet traditional treatments have problems. Scientists are now exploring a new frontier in 3-D printing: placing living cells directly within the human body to address such issues.
Bioprinters eject live cells to generate tissues and organs in the same way as 3-D printers lay down layers of material to make buildings. People on active waiting lists for organ donations—nearly 70,000 people in the United States alone, according to the group United Network for Organ Sharing—might one day be able to receive a bioprinted organ as a long-term goal for this idea. Although the capacity to print a whole heart or kidney in this fashion is likely years away, bioprinting more minor things like bone transplants is a feasible near-term aim. Living tissues printed outside the body, on the other hand, would still need implantation surgery, which sometimes includes extensive incisions that raise the risk of infection and prolong recovery times.
What if physicians could print cells within the body instead? The plan is to employ existing minimally invasive surgical procedures to inject 3-D printing equipment into patients through tiny incisions and then lay down replacement tissues. Surgical meshes to assist repair hernias and patches for the ovaries to assist cure infertility are two possible uses for “in vivo bioprinting.”
Because the necessary equipment is generally too big to access the digestive system and other centrally situated organs without invasive surgery, much of the past research on in vivo bioprinting has concentrated on treatments of skin and other tissues on the outer part of the body. Scientists in China intended to create a small bioprinting robot that could enter the human body with relative ease to treat stomach ulcers less invasively. According to the study’s senior author Tao Xu, a bioengineer at Tsinghua University in Beijing, the researchers employed established approaches for producing dexterous electrical devices, such as mechanical bees and cockroach-inspired robots.
The resultant tiny robot measures 30 millimeters wide (less than half the width of a credit card) and folds to 43 millimeters in length. It expands to 59 millimeters in length once inside a patient’s body and may begin bioprinting. “The researchers built smart mechanisms that make the system compact before entering the body but unfold to give a vast working surface once passed the tight constrictions of entry,” says David Hoelzle, a mechanical engineer at Ohio State University. The latter was not involved in the research.
The Chinese scientists attached the tiny robot to an endoscope (a long tube that may be introduced into physiological holes) and successfully snaked it down a curved conduit into a transparent plastic replica of a stomach in their studies. They utilized it to print gels containing human stomach lining and stomach muscle cells (cultured in a commercial facility) onto a lab dish. Over ten days, the printed cells remained alive and grew at a steady rate. “This is the first micro-robotics and bioprinting have been combined,” Xu explains.
Traditional gastric lesion therapies, according to the researchers, include drugs, which can take a long time to work and aren’t usually very successful; endoscopic surgery, which can only treat minor wounds; and endoscopically administered sprays, which can stop bleeding but aren’t particularly helpful in entirely healing more extensive damage. In vivo bioprinting can improve existing procedures by covering stomach ulcers with live structures that can mend them, according to Xu.
According to Xu, further research might reduce the tiny robot’s size to 12 millimeters and equip it with cameras and other sensors to do more sophisticated tasks. This summer, he and Tsinghua University’sUniversity’s Wenxiang Zhao published their findings in Biofabrication.
According to Xu and his colleagues, the gels employed as bioprinting “ink” were only stable when kept chilled. They were too liquid to form structures at typical body temperatures. Furthermore, the calcium chloride solution used by the researchers to help harden the gels might be harmful to humans. However, another gel, produced separately by Hoelzle and his colleagues, may be able to help with these issues: it can keep its structure at body temperature and solidify using visible light.
One of the difficulties with bioprinting is attaching printed cells to existing soft organs and tissues. Hoelzle and his colleagues tested a potential solution by trying to “heal” punctures in texturally similar materials—including raw chicken breast strips. First, the 3-D printer’s nozzle extruded a tiny knob of bio-ink into the puncture, creating an anchor that could connect the pierced tissue to a bioprinted structure. Then they slowly withdrew the nozzle, trailing behind a strand of material they could use to lay more cells on the outside of the tissue. Xu comments, “This work is illuminating.” He says that utilizing these strategies will aid in the advancement of in vivo bioprinting.
According to Hoelzle, the technique will almost certainly never be capable of manufacturing complicated organs. Instead, it might be beneficial by supplementing traditional procedures with small printed structures that release medications to aid healing or prevent infection. ” “There are numerous options for tissue engineering materials… that are now not being considered,” Hoelzle adds, “because no one wants to open up the patient to administer the material.”