Tag Archives: implant

Magnetic brain stimulation:New technique could lead to long-lasting localized stimulation of brain tissue without external connections.

By David Chandler


CAMBRIDGE, Mass–Researchers at MIT have developed a method to stimulate brain tissue using external magnetic fields and injected magnetic nanoparticles — a technique allowing direct stimulation of neurons, which could be an effective treatment for a variety of neurological diseases, without the need for implants or external connections.

The research, conducted by Polina Anikeeva, an assistant professor of materials science and engineering, graduate student Ritchie Chen, and three others, has been published in the journal Science.

Previous efforts to stimulate the brain using pulses of electricity have proven effective in reducing or eliminating tremors associated with Parkinson’s disease, but the treatment has remained a last resort because it requires highly invasive implanted wires that connect to a power source outside the brain.

“In the future, our technique may provide an implant-free means to provide brain stimulation and mapping,” Anikeeva says.

In their study, the team injected magnetic iron oxide particles just 22 nanometers in diameter into the brain. When exposed to an external alternating magnetic field — which can penetrate deep inside biological tissues — these particles rapidly heat up.

The resulting local temperature increase can then lead to neural activation by triggering heat-sensitive capsaicin receptors — the same proteins that the body uses to detect both actual heat and the “heat” of spicy foods. (Capsaicin is the chemical that gives hot peppers their searing taste.) Anikeeva’s team used viral gene delivery to induce the sensitivity to heat in selected neurons in the brain.

The particles, which have virtually no interaction with biological tissues except when heated, tend to remain where they’re placed, allowing for long-term treatment without the need for further invasive procedures.

“The nanoparticles integrate into the tissue and remain largely intact,” Anikeeva says. “Then, that region can be stimulated at will by externally applying an alternating magnetic field. The goal for us was to figure out whether we could deliver stimuli to the nervous system in a wireless and noninvasive way.”

The new work has proven that the approach is feasible, but much work remains to turn this proof-of-concept into a practical method for brain research or clinical treatment.

The use of magnetic fields and injected particles has been an active area of cancer research; the thought is that this approach could destroy cancer cells by heating them. “The new technique is derived, in part, from that research,” Anikeeva says. “By calibrating the delivered thermal dosage, we can excite neurons without killing them. The magnetic nanoparticles also have been used for decades as contrast agents in MRI scans, so they are considered relatively safe in the human body.”

The team developed ways to make the particles with precisely controlled sizes and shapes, in order to maximize their interaction with the applied alternating magnetic field. They also developed devices to deliver the applied magnetic field: Existing devices for cancer treatment — intended to produce much more intense heating — were far too big and energy-inefficient for this application.

The next step toward making this a practical technology for clinical use in humans “is to understand better how our method works through neural recordings and behavioral experiments, and assess whether there are any other side effects to tissues in the affected area,” Anikeeva says.

In addition to Anikeeva and Chen, the research team also included postdoc Gabriela Romero, graduate student Michael Christiansen, and undergraduate Alan Mohr. The work was funded by the Defense Advanced Research Projects Agency, MIT’s McGovern Institute for Brain Research, and the National Science Foundation.

Eye implant developed at Stanford could lead to better glaucoma treatments

Lowering internal eye pressure is currently the only way to treat glaucoma. A tiny eye implant developed by Stephen Quake’s lab could pair with a smartphone to improve the way doctors measure and lower a patient’s eye pressure.

BY BJORN CAREY


For the 2.2 million Americans battling glaucoma, the main course of action for staving off blindness involves weekly visits to eye specialists who monitor – and control – increasing pressure within the eye.

Now, a tiny eye implant developed at Stanford could enable patients to take more frequent readings from the comfort of home. Daily or hourly measurements of eye pressure could help doctors tailor more effective treatment plans.

Internal optic pressure (IOP) is the main risk factor associated with glaucoma, which is characterized by a continuous loss of specific retina cells and degradation of the optic nerve fiber. The mechanism linking IOP and the damage is not clear, but in most patients IOP levels correlate with the rate of damage.

Reducing IOP to normal or below-normal levels is currently the only treatment available for glaucoma. This requires repeated measurements of the patient’s IOP until the levels stabilize. The trick with this, though, is that the readings do not always tell the truth.

Like blood pressure, IOP can vary day-to-day and hour-to-hour; it can be affected by other medications, body posture or even a neck-tie that is knotted too tightly. If patients are tested on a low IOP day, the test can give a false impression of the severity of the disease and affect their treatment in a way that can ultimately lead to worse vision.

The new implant was developed as part of a collaboration between Stephen Quake, a professor of bioengineering and of applied physics at Stanford, and ophthalmologist Yossi Mandel of Bar-Ilan University in Israel. It consists of a small tube – one end is open to the fluids that fill the eye; the other end is capped with a small bulb filled with gas. As the IOP increases, intraocular fluid is pushed into the tube; the gas pushes back against this flow.

As IOP fluctuates, the meniscus – the barrier between the fluid and the gas – moves back and forth in the tube. Patients could use a custom smartphone app or a wearable technology, such as Google Glass, to snap a photo of the instrument at any time, providing a critical wealth of data that could steer treatment. For instance, in one previous study, researchers found that 24-hour IOP monitoring resulted in a change in treatment in up to 80 percent of patients.

The implant is currently designed to fit inside a standard intraocular lens prosthetic, which many glaucoma patients often get when they have cataract surgery, but the scientists are investigating ways to implant it on its own.

“For me, the charm of this is the simplicity of the device,” Quake said. “Glaucoma is a substantial issue in human health. It’s critical to catch things before they go off the rails, because once you go off, you can go blind. If patients could monitor themselves frequently, you might see an improvement in treatments.”

Remarkably, the implant won’t distort vision. When subjected to the vision test used by the U.S. Air Force, the device caused nearly no optical distortion, the researchers said.

Before they can test the device in humans, however, the scientists say they need to re-engineer the device with materials that will increase the life of the device inside the human eye. Because of the implant’s simple design, they expect this will be relatively achievable.

“I believe that only a few years are needed before clinical trials can be conducted,” said Mandel, head of the Ophthalmic Science and Engineering Laboratory at Bar-Ilan University, who collaborated on developing the implant.

The work, published in the current issue of Nature Medicine, was co-authored by Ismail E. Araci, a postdoctoral scholar in Quake’s lab, and Baolong Su, a technician in Quake’s lab and currently an undergraduate student at the University of California, Los Angeles.

Source: Stanford News