For a dozen years, ENT surgeon Anil Lalwani and mechanical engineer Jeffrey Kysar have been working together to develop a needle that can deliver gene therapies into the inner ear to treat hearing loss and other conditions.
“The key to precision medicine”
From the prestigious American University of Columbia, they have succeeded in developing “a micro-needle” using 3D printing. “It’s no exaggeration to say that our microneedling could be the key to precision medicine for the inner ear“, they estimate. To market their device, proven by more than 20 scientific publications, the researchers founded the company Haystack Medical.
Their objective is to answer the following problem: gene therapies will soon be able to restore hearing by regenerating inner ear cells. Gold, “we don’t really have a way to administer them“. Hence the idea of using 3D printing to manufacture the thinnest and sharpest needle possible, thus avoiding tearing the membrane of the cochlea, a spiral structure of the inner ear that transforms sound vibrations into electrical signals transmitted to the brain to enable hearing.
The two-photon photolithography process
To make the microneedle, they used two-photon photolithography. Particularly suitable for creating extremely precise and detailed structures, this technique is based on the use of a laser which will harden a photosensitive material only where two particles of light (photons) cross. The laser is moved in three dimensions to draw the patterns. “Our needles are much sharper than any commercially available needle.”says Jeffrey Kysar.
This technique makes it possible to obtain “voxel resolution [équivalent 3D d’un pixel en 2D, ndlr] about 200 nanometers [un nanomètre représente un milliardième de mètre]or about a tenth of a percent of the diameter of a hair“, explain the scientists.”We can print needles that are extremely sharp and made from polymers, like the epoxy you can buy at a hardware store“, they add.
Better diagnosis of Ménière’s disease
For more than 12 years, researchers have practiced “dozens and dozens of operations on animals” to perfect their microneedle, in particular to make it as strong as possible. It was notably used to inject a contrast agent into the internal cochlea in an animal to examine the size of the different sections of the cochlea with an MRI. The goal is to diagnose Ménière’s disease, in which the cochlear canal becomes much larger, and which causes attacks of vertigo accompanied by progressive loss of hearing. This step was detailed in an article published in November. 2024 in the scientific journal Academic Radiology.
The printed microneedle has also been used, successfully, in the injection of siRNA, a small RNA molecule capable of treating diseases by switching off the expression of specific genes that cause that disease. The manipulation did not cause perforation of the round window membrane, which closes a small opening at the base of the cochlea and is essential for the transmission of sound vibrations.
The next step is the clinical trial in humans. In this context, the two scientists are in discussions with companies developing gene therapies to test their innovation.
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