Nobody likes the process of getting vaccinated, particularly young children, some of whom are terrified of needles. But research presented in Sydney earlier this month opens the door to a painless alternative – one whose primary downside might be that it’s actually a bit boring.
And that’s just one way the latest in acoustical science can be used to address important medical problems, such as finding better ways to heal sports injuries, recover from strokes, and offset myopia caused by spending too much childhood time glued to phones, computer screens, and the television.
The occasion to bring on the research was a joint conference of the Acoustical Societies of Australia and America.
For most people, acoustics is synonymous with “how well can I hear you in a large room?” In medicine, it’s mostly about ultrasound.
That is simply high-frequency sound, pitched above the range of human hearing. It has long been used to image the inside of your body, including taking sonograms of unborn babies and monitoring blood flow through the heart and brain. Now, says Darcy Dunn-Lawless, an Australian PhD student at the University of Oxford, UK, it may also be usable to administer vaccines without need of a shot.
So far, ultrasound-induced vaccination has only been tested in mice, but initial results are impressive
It’s a concept straight from Star Trek. There, doctors like Bones McCoy or Beverly Crusher used a device called a hypospray, which painlessly squirted medicine into the skin, accompanied by a hiss like a suddenly opened can of soda. There was, of course, no explanation of how it worked, because at the time, no such technology existed. But Dunn-Lawless’s new method looks a lot like it, with the caveat that instead of a brief hiss, there’s a more prolonged burst of inaudible ultrasound.
It works via a process known as acoustic cavitation, which involves popping bubbles via vibrations induced by sound waves. “When these bubbles pop, [there is] a concentrated burst of mechanical energy, which you can use to do things,” Dunn-Lawless says.
In his procedure, the skin is dosed with a mix of microbubbles and the vaccine, then hit with ultrasound of the right frequency and intensity to pop the bubbles. That not only clears gaps through the outer layer of dead skin cells, but acts as a pump to force the vaccine through them and into the underlying layer of living cells. Better yet, it also opens gaps in the membranes of these cells, through which vaccines can make their way inside to start the processes leading to immunity – a process critical for the functioning of DNA-based vaccines.
So far, ultrasound-induced vaccination has only been tested in mice, but initial results are impressive. When compared to traditional vaccination, the immune response is significantly higher, apparently because of cavitation’s ability to drive the vaccine into the cells, rather than leaving most of it in the intercellular space, where it quickly breaks down. “It’s getting to the right place,” Dunn-Lawless says.
One caveat is that it’s not known for certain that the process is painless, because unlike Star Trek’s hypospray, it takes two minutes, and getting a mouse to hold still for it requires sedation. But there is no reason to believe it would hurt, Dunn-Lawless says, because it doesn’t force the vaccine more than a few hundred microns into the skin, well above the nearest pain sensors. “Nothing touches the endings of your nerves,” he says. Getting a squirming child to hold still for two minutes, of course, might be another issue. But it’s a lot better than getting them to submit to a shot.
Meanwhile, Sally McFadden of the University of Newcastle is using ultrasound to fight myopia. Globally, she says, there is an epidemic of nearsightedness among children around the world. “It’s now predicted that by 2050, half the world’s population will be myopic,” she says.
Myopia occurs when the eyeball grows too long. Close-up images can still focus on its retina, but long-distance ones don’t, and wind up blurred. It’s not just an issue of needing glasses: later in life, severe myopia can cause the retina to detach as the eye ages and its interior fluid shrinks.
People used to think the cause was genetic. But that’s not true. “You can’t blame your parents for your myopia,” McFadden says. Rather, she says, “it’s to do with what you are using your eyes for, what our children are using their eyes for” – which is often a lifestyle in which children, youth, and young adults spend too much time in environments where they are looking primarily at relatively close objects. The eyeball adapts to this, and grows into an elongated shape more conducive to that type of close focus, at the price of nearsightedness and increased risk of the retinal detachments later on. “The problem is that the human eye evolved to suit a hunter-gatherer lifestyle and is not adapted to modern living,” McFadden says. “We know that if children go outside, it can protect them from developing myopia.”
In part, these indoor/outdoor adaptations occur via changes in the sclera – the outer lining of the eyeball, part of which you can see in the mirror as the white of your eye. These adaptations can make it stronger and less likely to elongate, or weaker and more likely to do so.
One solution is for parents to force their children away from their devices, into a more varied outdoor environment. But there are also medical treatments that can strengthen the sclera and prevent it from too easily allowing the eyeball to elongate.
That, she says, is where ultrasound enters the process, because it is possible to use it to image the eyeball (the process involves numbing the cornea to allow the image to be taken without the patient being unduly discomfited) and examine the strength of the sclera. If that reveals that it is becoming weak and amenable to undue elongation, doctors can then determine what treatments can best be used to prevent that, without resorting to the near-impossible task of prying children away from their screens or the counterproductive task of asking ambitious students to limit their study time.
For those who do spend a lot of time away from their devices, Parag Chitnis, a bioengineering professor at George Mason University, Fairfax, Virginia, has another novel use of ultrasound: a wearable ultrasound system that can be used to monitor muscle function when on the move, whether it’s running, walking, or working out in the gym.
For the moment, his primary goal is to help athletes and others recover from injuries. But the same process can also be used to facilitate stroke rehabilitation, assess the risk of falls in the elderly, and help both elite and recreational athletes find their optimum training protocols.
Currently, if someone is injured or recovering from surgery, they go through physiotherapy and exercise programs based largely on the physical therapist’s experience and intuition. “We interviewed clinical-care providers,” Chitnis says, “and over and over, they said that if they could peel back the skin and look at the muscles [it would be a dream come true].”
That is exactly what his new technique can do, using stick-on ultrasound transducer/sensors that look like bits of athletic tape connected to a powerpack small and light enough to be belted to the hip without interfering with overall movement. “Our devices can be used to ensure that the muscle is actually being activated and used correctly,” Chitnis says.
Better yet, it’s all based on components that can be bought off the shelf and are affordable for physical therapy clinics, gyms, and sports teams. “These are basically components you can find in your car radio,” Chitnis says. “We envision, moving forward, that rehabilitation clinics will be able to purchase these systems for just a few hundred dollars.”