en.Wedoany.com Reported - Engineers at the Massachusetts Institute of Technology (MIT) have developed a non-invasive pacemaker that stimulates the heart using ultrasound. The device is designed as a small patch worn on the chest, potentially offering a surgery-free alternative to traditional cardiac implants in the future.
The core of this device is a stamp-sized patch, whose miniature transducers can send ultrasound pulses through the chest to stimulate the heart. The ultrasound triggers the opening of specific ion channels in heart cells, an effect amplified by researchers through genetic engineering. When the channels open, calcium ions enter the cells, signaling the heart cells to contract and beat. In laboratory experiments, researchers applied ultrasound to engineered human heart cells and found that the pulses effectively maintained healthy cell contractions. The team also tested the ultrasound patch on rats, showing that the device could quickly, safely, and non-invasively correct arrhythmias and restore a regular heart rhythm.
The research team has created a prototype, including the ultrasound patch and a small pocket-sized device containing a battery and electronics. The group previously demonstrated a patch design that uses ultrasound to image deep organs and tissues, and they plan to integrate both methods into a single patch to enable simultaneous monitoring and regulation of heart activity.
"We believe that in the future, we can stick a patch on the body to achieve long-term deep internal imaging and provide therapeutic stimulation in a non-invasive, closed-loop manner," said Xuanhe Zhao, a professor of mechanical engineering and civil and environmental engineering at MIT. He and collaborators from the team of Professor Qifa Zhou at the University of Southern California (USC) published their findings in the international journal *Nature Biomedical Engineering*. MIT co-authors of the study include first author Chen Gong, Runze Li, Won Jun Song, former postdoc Gengxi Lu, Shucong Li, Hsiao-Chuan Liu, and others, with collaborators also from teams at Harvard University, the University of California, Los Angeles, and USC.
Currently, about 3 million adults in the United States use pacemakers. These implantable devices are mature and generally safe, but they still carry surgical risks. "Pacemakers are one of the most important and widely used human implants, saving millions of lives," said co-corresponding author Gengxi Lu. "But they are invasive, in direct contact with the beating heart. The dream for years has been to achieve non-invasive cardiac stimulation using ultrasound." Scientists had previously observed that ultrasound affects the heart, but the effects were inconsistent and weak. In their research, Zhao's team applied a method called sonogenetics—drawing on optogenetics, which uses genetic manipulation to make specific parts of cells respond to light. Sonogenetics aims to genetically engineer cells to respond to sound, including ultrasound. In developing the pacemaker, the team used sonogenetics to increase the sensitivity of heart cells to ultrasound: they differentiated heart cells from embryonic stem cells using standard methods and then genetically modified them to produce ion channels that open more readily in response to ultrasound.
In experiments, genetically engineered heart cells beat in sync with ultrasound when exposed to it, while unmodified cells showed no such response. The team envisions that for future clinical applications, patients might first receive a one-time gene therapy injection (similar to a vaccine) to increase the sensitivity of their heart cells to ultrasound. Subsequently, the team designed a stamp-sized ultrasound pacemaker patch. Its adhesive layer is made of a hydrogel material that adheres firmly to the skin and allows ultrasound to pass through without attenuation. The patch contains miniature ultrasound transducers tunable to specific frequencies. In rat experiments, researchers first administered a sonogenetic ultrasound-enhancing solution via tail injection, then attached the miniature pacemaker patch to the rat's chest. When the patch was activated, the ultrasound quickly regulated the animals' heartbeats: individuals with slow heart rates returned to normal rates, those with arrhythmias stabilized, and the beats synchronized with the ultrasound pulses.
"Now we can use low-intensity ultrasound to open ion channels in cells, achieving very effective cardiac pacing," said first author Chen Gong. "We are making these patches smaller and more integrated, making them easier to wear, more stable, and more precise over the long term." Professor Xuanhe Zhao added, "In this paper, we demonstrated non-invasive pacing. But we believe this concept is not limited to the heart. We think that in the future, we can stick patches on different parts of the body to achieve long-term imaging, monitoring, and closed-loop therapeutic stimulation."
This work was supported in part by the National Institutes of Health, the National Science Foundation, Research to Prevent Blindness, and the U.S. Department of War.
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