Silicone Cube Monitors Cancer Progress and Treatment

R&D DIGEST

In a project that could dramatically change cancer detection, researchers have developed an implantable sensor using magnetic nanoparticles. A team at Harvard University and the Massachusetts Institute of Technology (MIT) has come up with a device that monitors a tumor's size and observes drugs delivered to the site.

“This project combines the sensing capabilities of nanoparticles and the versatility of a microfabricated implant to create a miniature sensor that would be read by magnetic resonance imaging (MRI),” says Grace Kim. She is a researcher at MIT's Division of Health Sciences and Technology.

The researchers employed a technique called implanted magnetic sensing, which uses nanoparticles made of crosslinked iron oxide and coated with dextran (sugar). Antibodies specific to target molecules are attached to the particle surface. Once target molecules are present, they bind to the particles, making them clump together. An MRI can detect such clumping.

Measuring 40–50 nm, the particles are enclosed in a 2-mm implantable silicone cube. Part of the device contains a semipermeable membrane window through which the nanoparticles are exposed to the tumor's environment.

“By enclosing the nanoparticles in a device with a semipermeable membrane, the nanoparticles will still be exposed to the tumor microenvironment, even if the tumor has abnormal blood flow,” says Kim. “And because the particles cannot escape the device, we can repeat measurements over time.” The sensor can monitor cancer biomarker concentrations, drug concentrations, pH, and other information at the tumor site.

The implant presents the advantage of reporting on conditions inside the tumor versus the information that is found via a blood sample. Also, the sensor can remain in the body for a longer period of time. The immune system often removes nanoparticle sensors that are administered via blood.

Implant development is still in its early stages, but the researchers have begun working on a prototype to conduct animal testing. They're looking for housing materials and will perform more-rigorous stability, packaging, and manufacturing research later.

They've also developed a system that detects a hormone (human chorionic gonadotropin) that is elevated in testicular and ovarian cancers. They're in the process of conducting in vitro testing of the first analyte and will begin in vivo testing this year. The next steps include making the sensor quantitative for cancer monitoring and identifying more cancer biomarkers.

The project leader is Michael Cima, professor of materials science and engineering at MIT. As part of the research funding, the National Cancer Institute provided a grant to establish the MIT-Harvard Center of Cancer Nanotechnology Excellence.

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