Resistance-Sensing Needle Identifies Target Destinations

A highly sensitive intelligent-injector for tissue-targeting (i2T2) needle can detect changes in resistance in order to properly and safely deliver medication, claims a new study.

Developed by researchers at the Massachusetts Institute of Technology (MIT, Cambridge, MA, USA), Harvard Medical School (HMS; Boston, MA, USA), and Brigham and Women’s Hospital (BWH; Boston, MA, USA), the i2T2 intelligent injector is a highly sensitive, completely mechanical device that senses loss of tissue resistance when encountering a softer tissue or a cavity, causing it to stop advancing the needle and deliver the payload. i2T2 feedback is instantaneous, which allows for better tissue targeting and minimal overshoot into an undesired location.

To test the device, the researchers used tissue from three animal models to examine delivery accuracy in the suprachoroidal (SCS), epidural, and peritoneal spaces, as well as subcutaneously. For example, they found it can be used to reliably deliver liquids to the SCS for a wide range of eye sizes, scleral thicknesses, and intraocular pressures. The injector could also deliver stem cells to the back of the eye that could be useful for regenerative therapies. The study was published on February 25, 2019, in Nature Biomedical Engineering.

“Targeting specific tissues using a conventional needle can be difficult, and often requires a highly trained individual. In the past century there has been minimal innovation to the needle itself, and we saw this as an opportunity to develop better, more accurate devices,” said senior corresponding author Professor Jeff Karp, PhD, of Brigham and Women’s Hospital. “We sought to achieve improved tissue targeting while keeping the design as simple as possible for ease of use.”

The SCS, which is located between the sclera and choroid in the back of the eye, has emerged as an important location for medication delivery. It is also a challenging site to target, because the needle must stop after transitioning through the sclera, which is less than one millimeter thick, to avoid damaging the retina. Additional tissues that are difficult to target include the epidural space around the spinal cord, used for epidural anesthesia, the peritoneal space in the abdomen, and subcutaneous tissue between the skin and muscles.

Related Links:
Massachusetts Institute of Technology
Harvard Medical School
Brigham and Women’s Hospital