Quantitative estimation of gold nanoshell concentrations in whole blood using dynamic light scattering.

We demonstrate a new nondestructive optical assay to estimate submicron solid particle concentrations in whole blood. We use dynamic light scattering (DLS), commonly used to estimate nanoparticle characteristics such as size, surface charge, and degree of aggregation, to quantitatively estimate concentration and thereby estimate the actual delivered dose of intravenously injected nanoparticles and the longitudinal clearance rate. Triton X-100 is added to blood samples containing gold (Au) nanoshells to act as a quantitative scattering standard and blood lysing agent. The concentration of nanoshells was determined to be linearly proportional (R(2) = 0.998) to the relative light scattering attributed to nanoshells via DLS as compared with the Triton X-100 micelles in calibration samples. This relationship was found to remain valid (R(2) = 0.9) when estimating the concentration of circulating nanoshells in 15-muL blood samples taken from a murine tumor model as confirmed by neutron activation analysis. Au nanoshells are similar in size and shape to other types of nanoparticles delivered intravascularly in biomedical applications, and given the pervasiveness of DLS in nanoscale particle manufacturing, this simple technique should have wide applicability toward estimating the circulation time of other solid nanoparticles.