Search

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 polytetrafluoroethylcne (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. 10.1021/ac100167v

We have developed an on-line analytical system involving microdialysis (MD) sampling, a carbohydrate membrane desalter (CMD), and an inductively coupled plasma mass spectrometer (ICPMS) system for the simultaneous determination of multiple trace metals in the extracellular fluid (ECF) in the brains of anesthetized rats. The microdialysate that perfused from the animal at a flow rate of 0.5 [micro]L/min was on-line transferred to the CMD to remove the high-sodium matrix, followed by ICPMS measurement. The role of the CMD in this on-line system was investigated in detail. With prior addition of EDTA to the microdialysate to form anionic complexes of the metal analytes and the use of N[H.sub.4]CI as a regenerant to exchange [Na.sup.-] with N[H.sub.4.sup.-] ions, both quantitative recovery of the trace metal analytes and quantitative removal of the sodium matrix could be achieved. Two experimental modes of the monitoring system were constructed. For those metals (e.g., Cu, Zn, and Mn) that existed at (sub)nanogram-per-milliliter concentrations in the microdialysate, the temporal resolution was 10 min when using a 10 [micro]L loop for sample collection, followed by CMD and ICPMS; for those elements (e.g., Ca and Mg) that existed at microgram-per-milliliter levels (or greater), near-real-time analysis was possible because the microdialysate could be led, by-passing the sample loop, directly to the CMD for desalting without any time delay. Further improvement of the temporal resolution for the low-concentration elements was not possible without decreasing the detection limits of mass detection. Among the eight trace metals tested using this on-line system, the method detection limits for Cu, Zn, Mn, Co, Ni, and Pb reached subnanogram-permilliliter levels; for electrolyte species such as Ca and Mg, the detection limits were in the range of 50-100 ng/mL. Analytical accuracy, expressed as spike recovery, was 100% [+ or -] 15% for all of the elements tested. We demonstrate the applicability of the proposed system through the successful measurement of the basal values of Ca, Mg, Cu, Zn, and Mn in the ECF of a living rat brain and through in vivo monitoring of the concentration profiles of Mn and Pt in the ECF after the injection of drugs (Mn[Cl.sub.2] and cisplatin) into the rats. This microdialysis system is the first to offer real-time, in vivo monitoring of trace elements such as Ca and Mg.

The article discusses the design and testing of a superconducting solenoid magnet for soft X-ray magnetic circular dichroism (SXMCD) experiments at the National Synchrotron Radiation Research Center (NSRRC). Results suggest the successful testing of the magnet at the maximum magnetic field for 8T at its designed current of 270 A.

A study was conducted to isolate and determine isoflavones and their glycosides from kudzu root, and to investigate the bioactivity of isolated compounds. The result indicates that both chemical structures and reactive oxygen species result in differences in antioxidant activity of isoflavones and their glycosides.

Energy-dispersive x-ray diffraction studies were performed to analyze the structure of phase transitions under high pressure. It was observed that the zinc blende to rock salt phase transition pressures of Zn0.93Mn0.07Se and Zn0.76Mn0.24Se bulk crystals are 11.8 +/- 1.5 and 9.9 +/- 0.5 GPa, respectively. The respective bulk moduli are 61.8 +/- 0.8 and 60.5 +/- 0.8 GPa. The pressure-induced zinc blende to rock salt structure phase transition was seen as an indication of the semiconductor to metal transition for Zn(sub 1-x)Mn(sub x)Se.

Reflectance spectroscopy was utilized to examine the light hole and heavy hole exciton splitting of ZnSe1-xSx epilayers that were grown on misoriented gallium arsenide (001) substrates. The composition of the layers were used to determine both exciton energies. Results showed that an increase in the incorporation of sulphur was noted due to misorientation of the substrate in both thin and thick epilayers.