Needle-free drug infusions one step closer

Pioneers of needle-free drug delivery have discovered a combination of heat and friction could make many medications smoother and more injectable. This paves the way for new and more highly concentrated drug formulations potentially being able to be delivered needle-free at home. 

Currently, many drugs – such as those used in cancer therapy – are made up of large proteins and are thick and gloopy. These are typically thinned down with saline, and the resultant low-concentration, high-volume liquid can only be delivered very slowly through an intravenous infusion in a clinic.

Now a team led by Dr James McKeage and Prof Andrew Taberner from the Auckland Bioengineering Institute (ABI) at Waipapa Taumata Rau, University of Auckland have found that viscous fluids tend to develop a slippery edge when formed into a high-speed jet; they then become self-lubricating when delivered using a needle-free jet injection.

The team found that this effect, in combination with preheating a drug to body temperature, could allow fluids up to 100 times more viscous than current drugs, to be effectively delivered needle free.  

McKeage says by heating liquid medications, concentrated viscous drugs could be injected through the skin instead of into a vein, allowing patients to perform and control the delivery at home or in the community rather than requiring a doctor or nurse in a hospital.

Initially, the research team uncovered the interesting slippery edge phenomenon using computational modelling.

“Our computer modelling indicated that very high temperatures and low viscosities were occurring in tiny layers of fluid at the very edge of a jet – the outer 0.01 mm. Because such a tiny layer of fluid was heating up, the peak temperatures would quickly dissipate into the surrounding fluid, and so, were hard to measure.”

To overcome this unique measurement challenge, the scientists fashioned a tiny copper tube with a temperature sensor smaller than the average human hair. They recorded outer layer temperatures rising to greater than 60°C.

Despite these high temperatures measured at the edge of the jet, further modelling showed less than 10 percent of the fluid experiences an increase in temperature of more than 10°C.

“Knowing what fraction of drug changes temperature and by how much is important,” says McKeage, “because drugs can degrade when exposed to high temperatures for extended periods.

“Our evidence suggests that we can get all the benefits of increasing injectability with the vast majority of the drug never experiencing a significant change in temperature.

McKeage says more research is needed to confirm the improved injectability without damaging the drug and to explore how variable these effects are over different drugs and drug classes.

 By Megan Fowlie