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Nowadays, the silver is widely used in the biological field and its biological safety catches great attention. It is important to know the distribution of silver ions within the biological organism and the toxic threshold concentration in the tissue. Therefore, a highly sensitive method for measurement of trace amount of silver ion in the medical biological samples is needed. With its high sensitivity for detection of metal ions, inductively coupled plasma mass spectrometry (ICP-MS) method is well suited for quantification of trace amount of silver ion in such samples, but method development is still in its infancy. Consequently, a simple and convenient method for determination of trace amount of silver in the animal serum, tissues or organs was developed, in which the samples were subjected to the microwave digestion, followed by the ICP-MS analysis. To begin with, the samples of serum, muscle, bone marrow, bone, heart, liver, spleen, and kidney were sequently processed in 5 mL of HNO3 and 2 mL of H2O2 solution. Then the samples were completely digested by microwave with the power of 2 000 watts. The temperature was raised gradually by 3-step program. Moreover, the data achieved were reproducible and the method was time saving and especially for large amounts of sample processing. Then the digested solutions were diluted to constant volume. Finally, the concentration of 107Ag in the samples was analyzed by the method of ICP-MS under the optimized conditions. Element yttrium (Y) was used as the internal standard to compensate for matrix suppression effect and improve the accuracy of measurement. For one thing, the analytical results showed that the detection limit of the trace element 107Ag was 0.98 μg · kg(-1), and furthermore, the correlation coefficient of standard curve was 0.999 9. For another thing, the recovery rate of the silver element ranged from 98% to 107%, which was calculated according to measured quantity before adding standard, adding standard and measured quantity after adding standard. At the same time, the relative standard deviation (RSD) of the method was in the range of 2.0%-4.3%. The concentrations of element silver in animal serum, tissues and organs were determined by the aboved method. The obtained results showed that silver ions were mainly accumulated in the liver after they were intaken into the body. The results suggested that the microwave digestion-ICP-MS method could accurately determine the trace element Ag in the body. The method developed has good feasibility and is suitable for the determination of trace element Ag in various types of medical and biological samples, especially for large quantities of biological samples. The process has the advantages of easysample processing and it is simple and convenient. In addition, the accurate results could be obtained in a short time with high sensitivity. Last but not least, the method provides the guidance for the determination of trace elements in other biological samples.

To investigate the feasibility of using perfusion culture bioreactor for bone mesenchymal stem cell proliferation in large scale beta-tricalcium phosphate (beta-TCP) scaffold.In the dynamic perfusion culture group, the porous beta-TCP cylindrical scaffolds combined with the sheep mesenchymal stem cells were continuously perfused with the complete alpha-MEM medium by a peristaltic pump for 1, 2 and 4 weeks. While in the static culture group, the hybrid constructs were immersed in the medium without perfusion for 2 and 4 weeks. The cell proliferation and distribution were examined by the daily glucose consumption, the cell viability and undecalcified histological study.The daily glucose consumption increased with time. The increase was much more evident in the first 2 weeks than in the last 2 weeks. The daily glucose consumption was higher in the dynamic culture group than in the static culture group. The cell viability also increased with time. It was higher in the dynamic culture group. In comparison to 2-week culture, the cell viability was significantly higher after 4-week culture in the dynamic culture group (P0.05), while it was not significantly different after 4-week culture in the static culture group (P0.05). Under dynamic perfusion culture, the mesenchymal stem cells survived and proliferated through the scaffolds. However, the mesenchymal stem cells survived and proliferated only in the peripheral pores of the scaffolds under static culture. Histomorphometrical study indicated that there were much more cells in dynamic culture group than in the static group. The cell/pore rate was not significantly different between 2-week static culture and 4-week static culture (P0.05). However, the cell/pore rate was significantly higher after 4-week dynamic culture than after 2-week dynamic culture (P0.05).Perfusion culture permitted the persistent nutrition supply and gas exchange into the centre of large scaffold. This perfusion bioreactor makes the mesenchymal stem cells survive and proliferate through a large three-dimensional scaffold.