MIT Researchers Develop Implantable Device To Monitor Cancer, Tissue Scaffold To Regrow Cartilage And Bone

Main Category: Cancer / Oncology
Also Included In: Medical Devices / Diagnostics;  Bones / Orthopedics
Article Date: 27 May 2009 - 4:00 PDT

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Surgical removal of a tissue sample is now the standard for diagnosing cancer. And while biopsies are accurate, they only offer a snapshot of the tumor at a single moment in time.

Monitoring a tumor for weeks or months after the biopsy, tracking its growth, and studying how it responds to treatment would be much more valuable, says Michael Cima, professor of materials science and engineering at the Massachusetts Institute of Technology, who has developed the first implantable device to do just that. "What this does is basically take the lab and put it in the patient," says Cima. The devices, which are designed to be implanted at the time of biopsy, could be tailored to monitor chemotherapy agents, allowing doctors to determine whether cancer drugs are reaching the tumors. They also can be designed to measure pH or oxygen levels, which would reveal a tumor's metabolism and response to therapy. The cylindrical, 5-millimeter implant contains magnetic nanoparticles coated with antibodies specific to the target molecules. Target molecules enter the implant through a semipermeable membrane, bind to the particles, and cause them to clump together -- a process that can be detected by MRI. The device is composed of polyethylene, which is commonly used in orthopedic implants. The semipermeable membrane, which allows target molecules to enter but traps the magnetic nanoparticles inside, is fabricated of polycarbonate, a compound used in many plastics. Cima's team studied the device by transplanting human tumors into mice, then using the implants to track levels of human chorionic gonadotropin, a hormone produced by human tumor cells, for more than a month. They reported their findings in ronics. Biosensors & Bioelectronics. Cima believes an implant to test for pH levels could be commercially available in a few years, followed by devices to test for complex chemicals such as hormones and drugs.

In another MIT development, researchers constructed a tissue scaffold that can stimulate bone and cartilage growth when transplanted into knees and other joints. The scaffold could offer a potential new treatment for sports injuries and other cartilage damage, such as arthritis, says Lorna Gibson, professor of materials science and engineering and co-leader of the research team with William Bonfield, professor of medical materials at Cambridge University, U.K. "If someone had a damaged region in the cartilage, you could remove the cartilage and the bone below it and put our scaffold in the hole," she explains. The new scaffold, which researchers described in a series of articles in the Journal of Biomedical Materials Research, could offer a more effective, less expensive, easier, and less painful alternative to conventional therapies, Gibson adds. The team started with an existing method to produce a skin scaffold composed of collagen from bovine tendon and glycosaminoglycan, a long polysaccharide chain. To mimic the structure of bone, they developed a technique to mineralize the collagen scaffold by adding sources of calcium and phosphate. They next created a two-layer, osteochondral scaffold to regenerate both bone and cartilage. When implanted into a joint, the scaffold can stimulate mesenchymal stem cells in the bone marrow to produce new bone and cartilage. During a 16-week study, the scaffold successfully stimulated bone and cartilage growth after being implanted in the knees of goats. The technology has been licensed to Orthomimetics, a British company that has started clinical trials in Europe.

Sources
Nanowerk and PhysOrg.com

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