This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Research is performed to elucidate toxicology and pharmacokinetics of thiol-capped CdSe, CdS, PbSe and PbS quantum dots (QDs) in vivo. QDs exhibit bright, photo-stable and size-tunable fluorescence and therefore, they are under extensive investigation as photo-tunable probes for biomedical imaging and diagnostics. However, the use of these nanomaterials on humans raises concerns due to the unknown health effects and toxicity, Understanding the pharmacokinetic behavior of these particles in biological systems requires both analytical and toxicology testing methods. In this project, we have examined the stability of Cd, Pb and Se against heating during dissolution of several biological samples for accurate quantification of nanoparticles. It was found that all there elements were stable to allow reliable determination without any significant losses unless dissolved samples are heated to dryness. The method developed is advantageous for measurement of total QD levels from organs of exposed animals. In an attempt to identify ionic metal and intact QDs, a hydride generation method was designed. Experimental conditions were optimized for selective measurement of ionic Cd, Pb and Se resulting from in vivo disintegration of the QDs in body. The use of hydride generation will elucidate the biological stability of the QDs. In another study, physical stability of the CdSe QDs was investigated by sonicating the solutions of CdSe QDs. It was found that sonication did not cause any disintegration on CdSe QDs regardless of particle size. This result is important as it affords a potential tool for extracting metal ions without altering the nanoparticle composition in the organs.