Fear of needles is a reason for some people not to be vaccinated against Covid-19. That fear is of all times: it is not without reason that different techniques have been developed for more than 150 years for injecting without a needle. The technique that is now being developed by UT scientist David Férnandez Rivas and his team has become increasingly safer. And the way to give the injection fluid speed is more precise to control as well as the penetration depth in the body. Reason enough for his PhD student Jelle Schoppink to compare the various options in a ‘perspective paper’ in the authoritative  Advanced Drug Delivery Reviews .

The needle-free injection, which uses a liquid jet that is heated and propelled by a laser, is a development that is in full swing at the UT and has also led to the foundation of the company FlowBeams. Being able to inject or tattoo without needles is a promising development: it removes barriers for people and also reduces the large mountain of medical waste. It is also important that the fluid jet is easily controllable: do not use more fluid than is necessary, and also dose at a shallow depth below the skin surface.

“There is growing evidence that it is important to deliver small volumes directly below the skin’s surface, that is in the dermis and epidermis. We are able to do this with laser-guided injection.”
Jelle Schoppink, researcher needle-free injection

CROSS-CONTAMINATION

That control was different during the needle-free mass vaccination in the mid- ^20th  century. The liquid got its propulsion thanks to a compressed and released spring. The penetration depth, at 2 to 10 millimeters, was large and not easy to control. When it also turned out that part of the blood came back into the injector and could thus infect others, the World Health Organization (WHO) put an end to this method of injecting.

LASER BENEFITS

The application of lasers seems to be the most promising in the last ten years, after experiments with, among other things, compressed gas and piezoelectric power transmission. The Physics of Fluids group of Detlef Lohse and Michel Versluis started at the University of Twente with laser-guided jets, using a so-called pulsed laser. The group of David Fernández Rivas now opts for a continuous laser. Among other things, the lower costs of the laser play a role in this. The control over the fluid dynamics is great in both cases: not only is there no injection fluid wasted, it is quite possible to inject precisely into the dermis or epidermis. The typical depth is then 0.1 millimeter to 1 millimeter. The fact that the injection liquid is heated by the laser does not seem to affect the performance negatively.

Also, given the issues with early techniques, it is quite possible to prevent jet firing back. Although the technique has not yet been tested on humans, tests on gels that resemble human skin and on pig skin look good. Although the nozzle still needs to be replaced at the moment, Schoppink estimates that this will no longer be necessary in the long term, so that the amount of waste is kept to a minimum.

SANDPAPER

This means that the injection with needles is not completely off the table. An alternative to completely needle-free injection is the use of microneedles that the UT has also worked on and that are manufactured with silicon technology. You hardly feel them, like a kind of sandpaper, and can also be used at a shallow depth and precisely. In combination with the laser-guided liquid jet, the microneedles could serve as a kind of ‘signpost’ for very precise administration in different places at the same time.

The broad ‘perspective’ article by Jelle Schoppink therefore not only provides the history and the current playing field with his competitors, but also explores the possibilities of combining techniques.

Original Article: FROM COIL SPRING TO LASER: NEEDLE-FREE INJECTION INCREASINGLY PRECISE

More from: University of Twente 

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