Circulation time estimates of optically active nanoparticles using a pulse photometer

Researchers employ increasingly complex sub-micron particles for oncological applications to deliver bioactive therapeutic or imaging compounds to known and unknown in vivo tumor targets. In practice, experimental homogeneity using nanoparticles can be difficult to achieve. While several imaging techniques have been previously shown to follow the accumulation of nanoparticles into tumor targets, a more rapid sensor that provides a quantifiable estimate of dose delivery and short-term systemic response could increase the clinical efficacy and greatly reduce the variability of these treatments. We have developed a pulse photometer that when placed on an optically accessible location will estimate the concentration of near-infrared absorbing nanoparticles. The goal is to monitor the accuracy of the delivered dose and the effective circulation time of nanoparticles immediately after intravenous delivery but prior to therapeutic intervention. We present initial tests of our prototype using murine models to assess its ability to quantify circulation half-life and nanoparticle concentration. Four mice were injected with nanoparticles and circulation half-life estimates ranged from 3- 43 minutes. UV-Vis spectrophotometry was used to independently verify these measurements using 5μL blood samples. Linear models relating the two methods produced R2 values of 0.91, 0.99, 0.88, and 0.24.