A needle-free glucose monitoring technology that would allow people with diabetes to measure blood sugar levels without traditional “finger-pricking” has been bought closer to reality by researchers at the Auckland Bioengineering Institute (ABI), University of Auckland, New Zealand.

The researchers focused on needle-free jet injection, an emerging but well-developed technique in which a drug is delivered directly with a high-speed narrow jet of fluid. In a study published in the Journal of Diabetes Science and Technology, led by ABI researchers Jiali Xu, a PhD candidate, and James McKeage, PhD, the team demonstrated for the first time that a jet injector could also be used for needle-free glucose monitoring to collect blood samples from humans—that is, release enough blood for glucose sampling, sans needles.  

People with diabetes typically need to measure their blood glucose concentration several times each day. They do so by pricking their fingers with a needle to release a drop of blood. A glucose meter then indicates how much insulin is required for the person to maintain their blood sugar.

Fingertips are the preferred site for blood sampling because they have a high density of blood vessels. However, the fingertips are also sensitive, and pain, skin damage, bruising, and risk of infection from regular “pricking” has spurred increasing efforts to develop needle-free glucose monitoring methods of blood testing for people with diabetes.

Jet injection has been the subject of years of research by the ABI Bioinstrumentation Lab at the ABI, University of Auckland, which includes developing jet injectors for delivering drugs such as insulin, nicotine, and local anesthetic for dental treatment. Xu and her team demonstrated that the technology could also be used to pierce the skin with a small volume of harmless saline solution, which would release enough blood for glucose concentration measurement—that is, for extraction rather than for injection.

The study involved 20 healthy participants, who each volunteered four fingertips. Participants received a lancet prick (the standard needle) and jet injection through three differently shaped and sized nozzles. 

“These were designed to mimic the wound left from a lancet prick, in the anticipation that it might release blood in a way similar to a lancet prick,” Xu says.

The study showed this to be true, with some nozzle shapes performing better than others. For instance, a slot-shaped nozzle released more blood than a circle-shaped nozzle. Most of the different jet injection nozzles were generally perceived to be no more painful than a standard lancet, and in some cases, less so. Participants were blinded by an opaque barrier that prevented them from seeing the procedure but allowed them to communicate with the practitioner. They were also asked to complete a questionnaire 24 hours later to reassess the level of pain, swelling, or bruising.

“When you know there’s not a device that is pricking your skin, you could speculate that people will find jet injection more acceptable,” says Andrew Taberner, PhD, head of the Bioinstrumentation Lab at the ABI, and Xu’s supervisor. “But we don’t have evidence to back that up. That wasn’t part of this study. We were first trying to find out if it worked, and it did.”

Taberner was pleased, but not surprised. 

“Diesel mechanics have known for years that you should never put your finger in front of a fuel injector, because it will inject fuel into your finger,” he says. “They found this out the hard way. But we’re taking advantage of what diesel mechanics discovered accidentally years ago, with a very small amount of harmless liquid, to deliberately release blood.”

The team is now investigating if they can use jet injection not only to release blood, but also to suck back to extract fluid. This would allow for the design of an even smaller nozzle. According to the researchers, the team has the technology, having developed the world’s first jet injection device that uses electric motors to pressurize the drug, which allows for more precise control than the more common spring-actuated jet injector.

“Our technology has the capability to both deliver and withdraw fluid,” Taberner says. “No other jet projection technology has that capacity.” 

Research into needle-free glucose monitoring injections is a long game, as is the potential commercialization of the technology, Taberner says. However, he believes Xu’s research will contribute to the ultimate aim of the development of a single lancet-free reversible technology that will allow for both blood sampling and insulin delivery based on the glucose measurement in one device. 

“I hope that this research will contribute to that, and to the improvement in human healthcare, especially in the management of diabetes,” Xu says.

Featured Image: Jiali Xu, leader of the jet injection study, is a researcher at the Auckland Bioengineering Institute at the University of Auckland. Photo: University of Auckland