Small is promising when it comes to illuminating tiny tumors or precisely delivering drugs, but many worry about the safety of nano-scale materials.
Now a team of scientists has created miniscule flakes of silicon that glow brightly, last long enough to slowly release cancer drugs, then break down into harmless by-products.
"It is the first luminescent nanoparticle that was purposely designed to minimize toxic side effects," said Michael Sailor, a chemistry professor at the University of California, San Diego who led the study.
Many nanoparticles tested in research labs are too poisonous for use in humans.
"This new design meets a growing need for non-toxic alternatives that have a chance to make it into the clinic to treat human patients," Sailor said.
The particles inherently glow, a useful property that is most commonly achieved by including toxic organic chemicals or tiny structures called quantum dots, which can leave potentially harmful heavy metals in their wake.
When the researchers tested their safer nanoparticles in mice, they saw tumors glow for several hours, then dim as the particles broke down. Levels dropped noticeably in a week and were undetectable after four weeks, they report in Nature Materials February 22.
This is the first sudy to image tumors and organs using biodegradable silicon nanoparticles in live animals, the authors say.
The particles begin as thin wafers made porous with an electrical current then smashed to bits with ultrasound. Additional treatment alters the physical structure of the flakes to make them glow red when illuminated with ultraviolet light.
Luminescent particles can reveal tumors too tiny to detect by other means or allow a surgeon to be sure all of a cancerous growth has been removed.
These nanoparticles could also help deliver drugs safely, the researchers report. The cancer drug doxorubicin will stick to the pores and slowly escape as the silicon dissolves.