Lasers and Ultrasound Combine to Pulverize Arterial Plaque

Lasers are one of the tools physicians can lean on to tackle plaque buildup on arterial walls, but current approaches carry a risk of complications and can be limited in their effectiveness. By bringing ultrasound into the mix, scientists at the University of Kansas have demonstrated a new take on this treatment that relies on exploding microbubbles to destroy plaque with greater safety and efficiency, while hinting at some unique long-term advantages.

Scientists have demonstrated a new technique to take out arterial plaque, using low-power lasers and ultrasound to break it apart with tiny bubbles

The novel ultrasound-assisted laser technique builds off what’s known as laser angioplasty, an existing treatment designed to improve blood flow in patients suffering from plaque buildup that narrows the arteries. Where more conventional treatments such as stents and balloon angioplasty expand the artery and compress the plaque, laser angioplasty destroys it to eliminate the blockage.

The laser is inserted into the artery with a catheter, and the thermal energy it generates turns water in the artery into a vapor bubble that expands, collapses and breaks up the plaque. Because this technique calls for high-power lasers, it has the potential to perforate or dissect the artery, something the scientists are looking to avoid by using low-power lasers instead.

They were able to do so in pork belly samples and ex vivo samples of artery plaque with the help of ultrasound. The method uses a low-power nanosecond pulsed laser to generate microbubbles, and applying ultrasound to the artery then causes these microbubbles to expand, collapse and disrupt the plaque.

In conventional laser angioplasty, a high laser power is required for the entire cavitation process, whereas in our technology, a lower laser power is only required for initiating the cavitation process,” said team member Rohit Singh. “Overall, the combination of ultrasound and laser reduces the need for laser power and improves the efficiency of atherosclerotic plaque removal.

The mix of lasers and ultrasound has shown potential in other areas of medicine, with Singh and his colleagues pursuing similar therapies to tackle abnormal microvessels in the eye that cause blindness and blood clots in the veins. We’ve also seen ultrasound used to explode tiny bubbles in cancer research, providing a way of wiping out cancerous cells within a tumor.


Breakthrough Opens New Method to Fight Alzheimer’s

During experiments in animal models, researchers at the University of Kansas (KU)  have discovered a possible new approach to immunization against Alzheimer’s disease (AD). Their method uses a recombinant methionine (Met)-rich protein derived from corn that was then oxidized in vitro to produce the antigen: methionine sulfoxide (MetO)-rich protein. This antigen, when injected to the body, goads the immune system into producing antibodies against the MetO component of beta-amyloid, a protein that is toxic to brain cells and seen as a hallmark of Alzheimer’s disease.

As we age, we have more oxidative stress, and then beta-amyloid and other proteins accumulate and become oxidized and aggregated – these proteins are resistant to degradation or removal,” said lead researcher Jackob Moskovitz, associate professor of pharmacology & toxicology at the KU School of Pharmacy. “In a previous 2011 published study, I injected mouse models of Alzheimer’s disease with a similar methionine sulfoxide-rich protein and showed about 30% reduction of amyloid plaque burden in the hippocampus, the main region where damage from Alzheimer’s disease occurs.”

The MetO-rich protein used by Moskovitz for the vaccination of AD-model mice is able to prompt the immune system to produce antibodies against MetO-containing proteins, including MetO-harboring beta-amyloid. The introduction of the corn-based MetO-rich protein (antigen) fosters the body’s immune system to produce and deploy the antibodies against MetO to previously tolerated MetO-containing proteins (including MetO-beta-amyloid), and ultimately reduce the levels of toxic forms of beta-amyloid and other possible proteins in brain.

According to Moskovitz, there was a roughly 50% improvement in the memory of mice injected with the methionine sulfoxide (MetO)-rich protein versus the control.

The findings have been just published in the peer-reviewed open-access journal Antioxidants.


Super Conductive Graphene Will Boost Solar Technology

In 2010, the Nobel Prize in Physics went to the discoverers of graphene. A single layer of carbon atoms, graphene possesses properties that are ideal for a host of applications. Among researchers, graphene has been the hottest material for a decade. In 2017 alone, more than 30,000 research papers on graphene were published worldwide.

Now, two researchers from the University of Kansas (KU), Professor Hui Zhao and graduate student Samuel Lane, both of the Department of Physics & Astronomy, have connected a graphene layer with two other atomic layers (molybdenum diselenide and tungsten disulfide) thereby extending the lifetime of excited electrons in graphene by several hundred times. The finding will be published on Nano Futures, a newly launched and highly selective journal.

The work at KU may speed development of ultrathin and flexible solar cells with high efficiency.

For electronic and optoelectronic applications, graphene has excellent charge transport property. According to the researchers, electrons move in graphene at a speed of 1/30 of the speed of light — much faster than other materials. This might suggest that graphene can be used for solar cells, which convert energy from sunlight to electricity. But graphene has a major drawback that hinders such applications – its ultrashort lifetime of excited electrons (that is, the time an electron stays mobile) of only about one picosecond (one-millionth of one-millionth of a second, or 10-12 second).

These excited electrons are like students who stand up from their seats — after an energy drink, for example, which activates students like sunlight activates electrons,” Zhao said. “The energized students move freely in the classroom — like human electric current.

The KU researcher said one of the biggest challenges to achieving high efficiency in solar cells with graphene as the working material is that liberated electrons — or, the standing students — have a strong tendency to losing their energy and become immobile, like students sitting back down.

The number of electrons, or students from our example, who can contribute to the current is determined by the average time they can stay mobile after they are liberated by light,” explains Zhao. “In graphene, an electron stays free for only one picosecond. This is too short for accumulating a large number of mobile electrons. This is an intrinsic property of graphene and has been a big limiting factor for applying this material in photovoltaic or photo-sensing devices. In other words, although electrons in graphene can become mobile by light excitation and can move quickly, they only stay mobile too short a time to contribute to electricity.”

In their new paper, Zhao and Lane report this issue could be solved by using the so-called van der Waals materials. The principle of their approach is rather simple to understand. “We basically took the chairs away from the standing students so that they have nowhere to sit,” Zhao said. “This forces the electrons to stay mobile for a time that is several hundred times longer than before.”

To achieve this goal, working in KU’s Ultrafast Laser Lab, they designed a tri-layer material by putting single layers of MoSe2, WS2 and graphene on top of each other.