How Iron Makes Silica Nanoparticles Biodegradable

Adding a pinch of iron to silica nanoparticles makes the material degrade more rapidly, chemists at the University of California, San Diego, report (J. Am. Chem. Soc., DOI: 10.1021/ja3036114). The discovery could pave the way to biodegradable forms of silica for ultrasound contrast imaging or drug delivery. Silica’s stability makes it problematic for medical applications. Tiny silica particles can cause health hazards by accumulating in the lungs, and they also linger in the liver and kidneys. Inspired by reports that cations could alter silica’s degradation rate, Kristina K. Pohaku Mitchell, Andrew C. Kummel, William C. Trogler, and Alexander Liberman doped iron(III) into hollow silica nanoshell structures. They surmised that iron-chelating drugs or powerful iron chelators present in living things might snatch iron from silica nanostructures to promote degradation. Sure enough, their iron-doped nanoshells collapsed and broke down after several days in solution, or several weeks in human blood serum, as shown by UV spectroscopy and scanning electron microscopy. They’re now following the fate of silica degradation products and evaluating the nanoshells as ultrasound markers for breast tumors.