In vivo monitoring of quantum dots in the extracellular space using push-pull perfusion sampling, online in-tube solid phase extraction, and inductively coupled plasma mass spectrometry.

To monitor the dynamic changes of extracellular quantum dots (QDs) in vivo in the livers of anesthetized rats, we developed an automatic online analytical system comprising push-pull perfusion (PPP) sampling, the established in-tube solid phase extraction (SPE) procedure, and inductively coupled plasma mass spectrometry (ICPMS). The method takes advantage of the retention of QDs onto the interior surface of a polytetrafluoroethylene (PTFE) tube as a means of extracting the QDs from complicated push-pull perfusates. For the injected QDs present in the liver extracellular fluid (ECF) at low picomolar levels, a temporal resolution of 10 min was required to collect sufficient amounts of QDs to meet the sensitivity requirements of the ICPMS system. To the best of our knowledge, this study is the first to exploit the PPP technique for the collection of QDs from living animals and PTFE tubing as a SPE adsorbent for the online extraction of QDs and the removal of biological matrix prior to ICPMS analysis of cadmium-containing inorganic nanocrystal. We confirmed the analytical reliability of this method from measurements of the spike recoveries of saline samples; in addition, we demonstrated the systems' applicability through in vivo monitoring of the time-dependent concentration profile of liver extracellular QDs in living rats after intravenous administration.