Shiny nanoparticles for new sensors
Every other week, some scientists say that they have found the perfect sensors to be used to detect environmental pollution or contamination of food products. Today, researchers at UC Davis say they have created luminescent nanoparticles that could also be used for medical diagnostics. These nanoparticles are coated in a shell of europium which emits red light at a very specific wavelength when stimulated with a laser. These nanoparticles, which are inexpensive to make, can also be manipulated with magnets and detected by fluorescence.
These nanoparticles have been created by an interdisciplinary team at UC Davis, led by Ian Kennedy, professor of mechanical and aeronautical engineering, who also works for the Biosensor group, in particular on the subject of fluorescence immunoassays. Here is how these nanoparticles are made.
The nanoparticles were made by spray pyrolysis, which involves mixing the raw material in a solvent and spraying it through a flame. The method is much cheaper than the techniques previously used for making similar particles, and can readily be scaled up to industrial production. It is already used in the chemical industry to make products such as fumed silica and carbon black.
Below are two -- not too shiny -- images of the magnetic separation of nanoparticles from an aqueous solution, before the liquid is removed (left) and after (right) (Credit:UC Davis, via the Institute of Physics). "The final core/shell particles were successfully separated from an aqueous solution by a commercially available permanent magnet for biochemical purposes, as shown in the figure. Initially, the particles that were suspended in water were attracted to the magnet and stuck to the glass wall (left). Afterwards, the water was pulled out of the tube leaving the particles in the tube (right)."
This research work has been published in Nanotechnology under the name "Magnetic/luminescent core/shell particles synthesized by spray pyrolysis and their application in immunoassays with internal standard" (Volume 18, Number 5, Article 055102, published online on January 9, 2007). Here is a link to the abstract of which here is an excerpt.
In this work we apply flame spray pyrolysis in order to engineer a novel type of nanoparticle that has both luminescent and magnetic properties. The particles have magnetic cores of iron oxide doped with cobalt and neodymium and luminescent shells of europium-doped gadolinium oxide. [...] Our synthesis method offers a low-cost, high-rate synthesis route that enables a wide range of biological applications of magnetic/luminescent core/shell particles.
And here is a link to the full paper (PDF format, 6 pages, 703 KB, article available free for 30 days, but after registration).
Finally, these nanoparticles can also "be coated with short pieces of DNA and used for genetic analysis. The team is exploring uses including testing for bioterrorism agents such as ricin or botulinum toxin in food and for genetic tests in cancer medicine."
Sources: UC Davis, January 25, 2007; and various other websites
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