Studying actinide biochemistry is challenging as easily detectable amounts of actinides tend to be too radiotoxic for in vivo studies. However, detection and mapping of fissile actinide elements through fission track analysis (FTA) can achieve detection limits of less than 1 femtogram per cell, with the use of topological standards. Liposomes, often called "cell mimics", spherical vesicles made of phospholipids capable of encapsulating known amounts of analyte when synthesized with methods that support encapsulation efficiencies near 100 %. The group of liposomes which are similar in size to mammalian cells are giant unilamellar vesicles (GUVs). In this work, the GUVs are synthesized using an inverted emulsion technique which allows a minimal amount of encapsulation solution to be used, making it compatible with handling plutonium (Pu). The Pu is chelated with diethylenetriamine pentaacetate (DTPA) to prevent the Pu from crossing the lipid bilayer to the external solution. The GUV standards encapsulate 1x10-15, 5x10-16, 1x10-16, 5x10-17, 1x10-17, and 5x10-18 grams of 239Pu in the presence of sucrose. Including sucrose stabilizes and immobilizes the GUVs into a sugar film while being air dried onto solid-state nuclear track detectors (SSNTDs) for fission track analysis (FTA). The resulting sugar film also greatly reduces the risk of dispersing the radioactive material. In FTA, fissile samples are deposited on SSNTDs comprised of solid insulating material with a very flat surface. The samples are exposed to low energy neutrons which split the atoms into fission products (FPs); 2 new naked nuclei traveling with kinetic energies ~100 MeV each moving apart at 180° from one another. One of the FPs will strike the SSNTD leaving a track of positively charged molecules and can be seen in a light microscope after chemical etching.

Giant unilamellar vesicles employed to encapsulate sub-femtogram standards of plutonium

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.