During breast tissue biopsies, rice grain-sized metal coils are often inserted to mark sites for future X-rays or ultrasounds. These “clips” allow clinicians to re-examine the exact location of potential tumors in the months post-biopsy. But unless surgeons need to remove the surrounding tissue, the clip remains in the body permanently. These clips pose no long-term health risks, but many patients find this permanence disturbing and opt out, says Zahava Gallimidi, a physician and director of the mammography unit at Rambam Health Care Campus in Israel. “Patients are asking me every day, ‘Where is a biodegradable clip?’”
To meet those requests, Gallimidi enlisted the help of polymer chemist Abraham J. Domb of the Hebrew University of Jerusalem. Domb and his team synthesized cylindrical clips by extruding a biodegradable polymer with an X-ray contrast agent. They also tested hydrogel coatings for some of the clips to improve visibility by magnetic resonance imagng (MRI) and ultrasound examination. The researchers implanted the clips in rats and tracked clip stability and visibility over 3–4 months using X-ray, MRI, and ultrasound. The best-performing clips had a core of poly(L-lactide-co-ε-caprolactone) and the contrast agent barium sulfate, surrounded by either hyaluronic acid or sodium alginate hydrogel (ACS Appl. Bio Mater. 2020, DOI: 10.1021/acsabm.0c00655). Both Gallimidi and Domb are optimistic about translating their findings to a clinical trial. None of the clips caused any adverse side effects, and Domb says the clips should fully degrade and be eliminated from the body after about 12 months.