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New device delivers medicine directly to the inner ear

Contributed by | Thursday, March 17th, 2016

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A team of engineers and scientists have collaborated to come up with a more effective way to treat certain types of hearing loss, and after years of hard work their efforts have finally come to fruition.

Stylized graphic of hypodermic needle
A new method of drug delivery to
the inner ear may help monitor
concentrations of ototoxic drugs.
 

Draper engineers worked with scientists at Massachusetts Eye and Ear to develop an implantable device capable of delivering medicine directly to the cochlea. The battery-operated device, approximately the size of a golf ball, operates by a micro pump that delivers drugs directly to the cochlea. In addition to the micro pump, the device also consists of a drug reservoir and a small tube.

The pump and drug reservoir are surgically implanted in the temporal bone of the ear, with the tube injecting drugs into the cochlea.

According to the National Institute on Deafness and Other Communication Disorders (NIDCD), 48 million people in the U.S have hearing loss. Untreated hearing loss can cause a cascade of negative effects including depression, anger, poor interpersonal relationships and reduced quality of life, not to mention the detrimental effects on physical health and personal safety. While many forms of hearing loss can’t be cured, it is possible that other forms of hearing loss (such as hearing loss as a result of ototoxic medications) could be prevented or even stopped in their tracks with new forms of intervention.

The reason for the importance of this latest invention is that previous methods of drug delivery haven’t been as effective as researchers and doctors would have liked. Due to the fact that the cochlea is located deep within the temporal bones and protected from the rest of the body by fluid filled canals and membranes, it is difficult to reach.

“It takes some heroic efforts to get compounds into the inner ear,” said Sharon Kujawa, director of audiology at the Massachusetts Eye and Ear Infirmary and associate professor at Harvard Medical School, and part of the development team. “It’s our view that with all of the effort going on in drug discovery around the world, some attention needs to paid to how those compounds are going to get to the inner ear.”

Other methods of drug delivery that have been tried are injections to the middle ear, also known as intratympanic delivery, and systemic drug delivery. Intratympanic delivery relies on indirect transport of the drug through a barrier called the round window membrane, and sometimes requires multiple injections.

With intratympanic delivery the drugs are injected into a space behind the eardrum, and since they diffuse into the inner ear over time, it is impossible to control the quantities of drug that reach the cochlea. But the new device solves that problem by allowing a monitored dosage schedule directly to the cochlea. In addition, the new implantable device will also allow the administration of more than one drug at a time, a task which is not possible with other methods of drug delivery.

Systemic delivery, while easy and convenient for the patient, also has its drawbacks. The problem with systemic delivery, which encompasses the whole “system” and refers to most medications taken orally or by injection elsewhere in the body, is that a high level of drugs must be given in order to achieve therapeutic levels in one particular part of the body, in this case the cochlea. And those high levels of drugs can often come with negative side effects.The new device solves this problem as well.

“Ultimately, this device should be useful for delivering drugs where and when they are needed, in a concentration where they can be effective, and without unwanted systemic side effects,” said Kujawa.

In addition to more direct and effective drug delivery, the device can also assess drug concentration in the cochlea, a necessary step which may help propel the device toward FDA approval.

“If you can’t be sure of the amount of drug reaching the cochlea, the auditory portion of the inner ear targeted by new drugs, you can’t be sure that the candidate drug is responsible for changes in hearing during treatment,” said Jeff Borenstein, principal investigator for the intracochlear drug delivery device at Draper Laboratory. “Our device is capable of clearly showing whether the desired concentration of the drug is reaching the inner ear.” 

Although the device can’t treat all forms of hearing loss, future applications could include preventing hearing loss as a result of ototoxic medications or regenerating delicate hair cells within the inner ear. After successful testing on guinea pigs, the next step is testing on humans. Other future plans could include partnerships with pharmaceutical companies.

“All of those companies are looking to deliver drugs into the inner ear using some technology. We’re trying to fill that gap,” Borenstein said.

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