Europium Nanoparticles That Screen for Bacillus Anthracis

The US Food and Drug Administration has conducted a proof-of-concept study assessing the viability of using nanoparticles, made out of the element europium, to detect the anthrax bacteria. The test actually looks for the protective antigen (PA) protein that Bacillus anthracis produces, and initial findings show that the new detection method is highly effective.
From an FDA statement:

The proof-of-concept study developed by FDA researchers relies on a nanotechnology-based test platform built from tiny molecular-sized particles. This assay, the europium nanoparticle-based immunoassay (ENIA), was able to detect the presence of a protein made by the anthrax bacteria known as protective antigen (PA). PA combines with another protein called lethal factor to form anthrax lethal factor toxin, the protein that enters cells and causes toxic effects.
The researchers showed that ENIA is capable of detecting PA in quantities that are 100 times lower than current tests, such as the enzyme-linked immunosorbent assay (ELISA). Both the ELISA and ENIA rely on antibodies that have an affinity for the anthrax protein of interest.
The FDA test is a modified version of ELISA, which is already commonly used to detect anthrax and other infections. The researchers call their new test ‘europium nanoparticle-based immunoassay,’ because atoms of europium are key to the assay’s sensitivity.
The ENIA uses molecular spheres (called nanospheres) covered with thousands of light-emitting atoms of europium that emit light, which acts as a signal that PA is present. The CBER team further enhanced the signal by modifying the nanospheres so they held additional atoms of europium, making the test more sensitive.
The ENIA detected PA in 100 percent of samples of mouse plasma compared to 36.4 percent through ELISA.

Abstract in Clinical and Vaccine Immunology…
Image: Color-enhanced scanning electron micrograph shows splenic tissue from a monkey with inhalational anthrax; featured are rod-shaped bacilli (yellow) and an erythrocyte (red) Credit: NIH