New Tiny Implanted Pumps Can Inject Drugs Directly Into Brains
Scientists at Massachusetts Institute of Technology have developed a radical new way to treat neurodegenerative disorders like Parkinson’s disease, and it sounds pretty freaking sci-fi. Their procedure involves implanting a thin probe connected to a tiny pump into a patient’s brain that delivers precisely measured and targeted drugs to specific brain areas. While this brain implant pump is a long way off from being installed in human patients, it has shown promise in an initial study in laboratory animals, treating Parkinson’s-like symptoms in lab rats and monkeys.
The MIT researchers published their findings in a paper on Wednesday in the journal Science Translational Medicine. The main idea behind their device, called a “miniaturized neural drug delivery system” (MiNDS), is that it can precisely treat specific clusters of neurons without causing side effects. This improves upon previous methods that introduce drugs into the cerebrospinal fluid, which can also cause off-target effects.
Currently, people living with neurodegenerative conditions like Parkinson’s disease face seemingly impossible alternatives: They can either let their disease progress as symptoms like tremors and loss of balance worsen, or they can take drugs that have unintentional, off-target effects. These days, one of the most common therapies for Parkinson’s disease is the combination of drugs carbidopa and levodopa (usually under the brand name Sinemet), which can alleviate symptoms but also creates some long-term side effects that impair patients’ voluntary muscular movement.
One of the major advantages of the brain implants, the study’s authors write, is that it allows doctors to target highly specific functional areas of the brain as small as one cubic millimeter — about the height and length of one letter on the U.S. penny. Not only that, but they can actually measure the activity of neurons in the area being treated, enabling them to monitor a drug’s effects and alter drug delivery in real time.
They validated their concept in rhesus macaque monkeys and rats, first by inducing a parkinsonian state — one where dopamine-releasing neurons are dead or disabled — in both animals. They then treated the condition in the monkeys by injecting artificial cerebrospinal fluid into the MiNDS device. Throughout the experiments, the researchers monitored the animals’ brain activity using a tungsten probe in the device, which showed that the MiNDS implant could excite and inhibit specific neurons.
“We show here that MiNDS can chemically modulate the local neuronal activity and related behavior in animal models while simultaneously recording neuronal electroencephalogram (EEG) activity,” write the paper’s authors.
The idea that a person could get a brain implant instead of taking pills three times a day for the rest of their life sounds great, but this radical treatment protocol brings up some significant issues, too. The most obvious one is that implanting a deep brain drug delivery device is invasive as heck. This is not a simple procedure like getting a tattoo or a piercing; the proposed device penetrates deep into brain tissue, which raises concerns about complications that could arise as a result of something as complex as device malfunction or something as simple as bumping your head.
Additionally, placing a foreign object into brain tissue can cause surrounding tissue to become inflamed and potentially die. The researchers worked around this issue by using stainless steel and borosilicate (glass) as the main materials for the probe, which they say caused minimal damage to surrounding tissue in the test animals after eight weeks of implantation.
Perhaps most importantly, chemically induced Parkinson’s-like symptoms in mice and monkeys are quite different from those of actual Parkinson’s disease in humans. Before the MiNDS device could be anywhere near ready for humans, the researchers will need to demonstrate its effectiveness against Parkinson’s disease.
For now, though, it’s a fascinating development in the rapidly growing field of brain medicine.
Abstract: Recent advances in medications for neurodegenerative disorders are expanding opportunities for improving the debilitating symptoms suffered by patients. Existing pharmacologic treatments, however, often rely on systemic drug administration, which result in broad drug distribution and consequent increased risk for toxicity. Given that many key neural circuitries have sub–cubic millimeter volumes and cell-specific characteristics, small-volume drug administration into affected brain areas with minimal diffusion and leakage is essential. We report the development of an implantable, remotely controllable, miniaturized neural drug delivery system permitting dynamic adjustment of therapy with pinpoint spatial accuracy. We demonstrate that this device can chemically modulate local neuronal activity in small (rodent) and large (nonhuman primate) animal models, while simultaneously allowing the recording of neural activity to enable feedback control.