Ultrasound to Command Bacteria to Nuke Tumors

Scientists at Caltech have genetically engineered, sound-controlled bacteria that seek and destroy cancer cells. In a new paper appearing in the journal Nature Communications, researchers from the lab of Mikhail Shapiro, professor of chemical engineering and Howard Hughes Medical Institute investigator, show how they have developed a specialized strain of the bacteria Escherichia coli (E. coli) that seeks out and infiltrates cancerous tumors when injected into a patient’s body. Once the bacteria have arrived at their destination, they can be triggered to produce anti-cancer drugs with pulses of ultrasound.

The goal of this technology is to take advantage of the ability of engineered probiotics to infiltrate tumors, while using ultrasound to activate them to release potent drugs inside the tumor,” Shapiro says.

The starting point for their work was a strain of E. coli called Nissle 1917, which is approved for medical uses in humans. After being injected into the bloodstream, these bacteria spread throughout the body. The patient’s immune system then destroys them—except for those bacteria that have colonized cancerous tumors, which offer an immunosuppressed environment.

To turn the bacteria into a useful tool for treating cancer, the team engineered them to contain two new sets of genes. One set of genes is for producing nanobodies, which are therapeutic proteins that turn off the signals a tumor uses to prevent an anti-tumor response by the immune system. The presence of these nanobodies allow the immune system to attack the tumor. The other set of genes act like a thermal switch for turning the nanobody genes on when the bacteria reaches a specific temperature.

By inserting the temperature-dependent and nanobody genes, the team was able to create strains of bacteria that only produced the tumor-suppressing nanobodies when warmed to a trigger temperature of 42–43 degrees Celsius. Since normal human body temperature is 37 degrees Celsius, these strains do not begin producing their anti-tumor nanobodies when injected into a person. Instead, they quietly grow inside the tumors until an outside source heats them to their trigger temperature.

But how do you heat bacteria that are located in one specific location, potentially deep inside the body where a tumor is growing? For this, the team used focused ultrasound (FUS). FUS is similar to the ultrasound used for imaging internal organs, or a fetus growing in the womb, but has higher intensity and is focused into a tight point. Focusing the ultrasound on one spot causes the tissue in that location to heat up, but not the tissue surrounding it; by controlling the intensity of the ultrasound, the researchers were able to raise the temperature of that tissue to a specific degree.

Source: https://www.caltech.edu/

How to Control Neurons in the Brain

Researchers out of San Diego’s Salk Institute have gotten mice to move their limbs by stimulating brain cells using ultrasound. When mice were engineered to have their brain cells produce a special protein, the researchers found that hitting them with ultrasoundturned on” the cells, causing small, but perceptible, movements in their limbs. The technique, called “sonogenetics,” is the latest in a line of methods that look to stimulate and alter neurons directly, without using drugs.

We’ve spent so much time over the last few decades focusing on pharmacologic therapies,” said Colleen Hanlon, a biologist at Wake Forest not involved with the study. “This paper is another really important piece to this puzzle of developing neural circuit-based therapeutics for disease.”

 Sonogenetics is just one of the ways researchers have begun controlling neurons in the brain, turning them off or on at will. Perhaps the most well-known method is using electrical stimulation. In deep brain stimulation, researchers surgically implant electrodes into specific areas of the brain. When these electrodes fire off at the right time and with the right frequency, they can make tremors disappear, improve memory, and even treat depression.

Taking a step up on the wildness scale, scientists can also activate, or turn off, neurons using light, a technique called optogenetics. Optogenetics works by genetically engineering brain cells to produce light-sensitive proteins, which can be hit with a laser, causing the neuron to fire or not. A similar mechanism is behind sonogenetics, except the protein reacts to ultrasound. Ultrasound is appealing because of its well-understood safety profile and the fact that it is already used to target locations deep within the body. “Ultrasound is safe, noninvasive, and can be easily focused through thin bone and tissue to volumes of a few cubic millimeters,” the researchers wrote in their study, published in Nature Communications.

In optogenetics, by contrast, because skin and bone are opaque, even powerful lights will have a hard time reaching neurons deeper than the outer layer of the brain. Salk neuroscientist Sreekanth Chalasani and his colleagues pioneered sonogenetics several years ago in a tiny worm called a nematode. In the worms, they used an ultrasound-reacting protein called TRP-4. But when they put it into mammalian cells, well … nada. And thus began a six-year quest to find an ultrasound-reactive protein that works in mammals. They found it — a protein called TRPA1. The researchers first tested the protein in mouse neurons in the lab. When those cells reacted to ultrasound by producing electrical signals, they engineered it into living mice. When the TRPA1-producing mice were exposed to ultrasound, electrical signals coursed through their limbs — and a little bit of movement, too.

It’s a very exciting contribution and an important step,” adds Caltech sonogenetics researcher Mikhail Shapiro, who was uninvolved with the work.  “This is one of the papers that’s come out over the last several years that shows that it’s a real possibility that you can use ultrasound to directly modulate the activity of specific neurons.”

Source: https://www.freethink.com/

Ultrasound Can Selectively Kill Cancer Cells

A new technique could offer a targeted approach to fighting cancer: low-intensity pulses of ultrasound have been shown to selectively kill cancer cells while leaving normal cells unharmed.

Ultrasound wavessound waves with frequencies higher than humans can hear—have been used as a cancer treatment before, albeit in a broad-brush approach: high-intensity bursts of ultrasound can heat up tissue, killing cancer and normal cells in a target area. Now, scientists and engineers are exploring the use of low-intensity pulsed ultrasound (LIPUS) in an effort to create a more selective treatment.

A study describing the effectiveness of the new approach in cell models was published in Applied Physics Letters. The researchers behind the work caution that it is still preliminary—it still has not been tested in a live animal let alone in a human, and there remain several key challenges to address—but the results so far are promising.

The research began five years ago when Caltech‘s Michael Ortiz, Frank and Ora Lee Marble Professor of Aeronautics and Mechanical Engineering, found himself pondering whether the physical differences between cancer cells and healthy cells—things like size, cell-wall thickness, and size of the organelles within them—might affect how they vibrate when bombarded with sound waves and how the vibrations might trigger cancer cell death.

I have my moments of inspiration,” Ortiz says wryly.

And so Ortiz built a mathematical model to see how cells would react to different frequencies and pulses of sound waves. Together with then-graduate student Stefanie Heyden (PhD ’14), who is now at ETH Zurich, Ortiz published a paper in 2016 in the Journal of the Mechanics and Physics of Solids showing that there was a gap in the so-called resonant growth rates of cancerous and healthy cells. That gap meant that a carefully tuned sound wave could, in theory, cause the cell membranes of cancerous cells to vibrate to the point that they ruptured while leaving healthy cells unharmed. Ortiz dubbed the process “oncotripsy” from the Greek oncos (for tumor) and tripsy (for breaking).

Source: https://www.caltech.edu/

How To Levitate Objects With Light

Researchers at Caltech have designed a way to levitate and propel objects using only light, by creating specific nanoscale patterning on the objects’ surfaces. Though still theoretical, the work is a step toward developing a spacecraft that could reach the nearest planet outside of our solar system in 20 years, powered and accelerated only by light. The research was done in the laboratory of Harry Atwater, Howard Hughes Professor of Applied Physics and Materials Science in Caltech’s Division of Engineering and Applied Science.

Decades ago, the development of so-called optical tweezers enabled scientists to move and manipulate tiny objects, like nanoparticles, using the radiative pressure from a sharply focused beam of laser light. This work formed the basis for the 2018 Nobel Prize in Physics. However, optical tweezers are only able to manipulate very small objects and only at very short distances. Ognjen Ilic, postdoctoral scholar and the study’s first author, gives an analogy: “One can levitate a ping pong ball using a steady stream of air from a hair dryer. But it wouldn’t work if the ping pong ball were too big, or if it were too far away from the hair dryer, and so on.”

With this new research, objects of many different shapes and sizes—from micrometers to meters—could be manipulated with a light beam. The key is to create specific nanoscale patterns on an object’s surface. This patterning interacts with light in such a way that the object can right itself when perturbed, creating a restoring torque to keep it in the light beam. Thus, rather than requiring highly focused laser beams, the objects’ patterning is designed to “encode” their own stability. The light source can also be millions of miles away.

“We have come up with a method that could levitate macroscopic objects,” says Atwater, who is also the director of the Joint Center for Artificial Photosynthesis. “There is an audaciously interesting application to use this technique as a means for propulsion of a new generation of spacecraft. We’re a long way from actually doing that, but we are in the process of testing out the principles.”

In theory, this spacecraft could be patterned with nanoscale structures and accelerated by an Earth-based laser light. Without needing to carry fuel, the spacecraft could reach very high, even relativistic speeds and possibly travel to other stars.

Atwater also envisions that the technology could be used here on Earth to enable rapid manufacturing of ever-smaller objects, like circuit boards.

A paper describing the research appears online in the journal Nature Photonics.

Source: https://www.caltech.edu/

Molecular Nanocomputers

Computer scientists at Caltech have designed DNA molecules that can carry out reprogrammable computations, for the first time creating so-called algorithmic self-assembly in which the same “hardware” can be configured to run differentsoftware.”

A team headed by Caltech‘s Erik Winfree (PhD ’98), professor of computer science, computation and neural systems, and bioengineering, showed how the DNA computations could execute six-bit algorithms that perform simple tasks. The system is analogous to a computer, but instead of using transistors and diodes, it uses molecules to represent a six-bit binary number (for example, 011001) as input, during computation, and as output. One such algorithm determines whether the number of 1-bits in the input is odd or even, (the example above would be odd, since it has three 1-bits); while another determines whether the input is a palindrome; and yet another generates random numbers.

Think of them as nano apps,” says Damien Woods, professor of computer science at Maynooth University near Dublin, Ireland, and one of two lead authors of the study. “The ability to run any type of software program without having to change the hardware is what allowed computers to become so useful. We are implementing that idea in molecules, essentially embedding an algorithm within chemistry to control chemical processes.”

The system works by self-assembly: small, specially designed DNA strands stick together to build a logic circuit while simultaneously executing the circuit algorithm. Starting with the original six bits that represent the input, the system adds row after row of molecules—progressively running the algorithm. Modern digital electronic computers use electricity flowing through circuits to manipulate information; here, the rows of DNA strands sticking together perform the computation. The end result is a test tube filled with billions of completed algorithms, each one resembling a knitted scarf of DNA, representing a readout of the computation. The pattern on each “scarf” gives you the solution to the algorithm that you were running. The system can be reprogrammed to run a different algorithm by simply selecting a different subset of strands from the roughly 700 that constitute the system.

We were surprised by the versatility of programs we were able to design, despite being limited to six-bit inputs,” says David Doty, fellow lead author and assistant professor of computer science at the University of California, Davis. “When we began experiments, we had only designed three programs. But once we started using the system, we realized just how much potential it has. It was the same excitement we felt the first time we programmed a computer, and we became intensely curious about what else these strands could do. By the end, we had designed and run a total of 21 circuits.”

The findings have been reported in the journal Nature.

Source: https://www.caltech.edu/

Immunotherapy Technique Specifically Targets Tumor Cells

A new immunotherapy screening prototype developed by University of California, Irvine (UCI) researchers can quickly create individualized cancer treatments that will allow physicians to effectively target tumors without the side effects of standard cancer drugsUCI’s Weian Zhao and Nobel laureate David Baltimore with Caltech led the research team that developed a tracking and screening system that identifies T cell receptors with 100-percent specificity for individual tumors within just a few days.

In the human immune system, T cells have molecules on their surfaces that bind to antigens on the surface of foreign or cancer cells. To treat a tumor with T cell therapy, researchers must identify exactly which receptor molecules work against a specific tumor’s antigens. UCI researchers have sped up that identification process.

This technology is particularly exciting because it dismantles major challenges in cancer treatments,” said Zhao, an associate professor of pharmaceutical sciences. “This use of droplet microfluidics screening significantly reduces the cost of making new cancer immunotherapies that are associated with less systemic side effects than standard chemotherapy drugs, and vastly speeds up the timeframe for treatment.

Zhao added that traditional cancer treatments have offered a one-size-fits-all disease response, such as chemotherapy drugs which can involve systemic and serious side effects.

Research findings appear in Lab on a Chip.

Source: https://news.uci.edu/