超聲兩種可混溶流體流之間的細胞分離和運輸

The voltage applied on the piezo-ceramic is 20 Vpp for all the experiments. At this working condition, no acoustic cavitation and no acoustic streaming were observed, as the acoustic intensity was found to be low (about 75 mW/cm2). Furthermore, since the transducer is directly driven by the function generator without any power amplifier, the driving current was very low, about several milli-amperes for the applied voltage of 20 Vpp. The power dissipation by the piezo-ceramic transducer is very small and no temperature change was observed in the experiments. The flow of species in the fluid channel is observed through the top glass cover via a microscope with a CCD camera (Leica Microsystems Vetzlar GmbH). Typical flow rate of the fluid used in the following experimental studies varies from hundreds of μL/h to several mL/h. These flow rates correspond to the Reynolds number in the range of Re ≈ 0.3–0.5, meaning that the flow within the channel is laminar.

Preparation of cell samples

To stain the parasite cells, both of the C. parvum and G. lamblia were separately mixed with their corresponding antibodies. The mixtures were incubated at 37?°C for 30?min. The parasite cells were then collected via centrifugation and were reconstituted into a drinking water solution. A 1?ml syringe was then used to contain the suspensions of cells and was connected to the inlet of the acoustic chip. A syringe pump (New Era Pump SystemTM) was used to purge the channel as well as to flow the cell samples into the channel.

Cell separation analysis and viability test

For cell separation analysis, the cells obtained from the outlets of the channel were collected and centrifuged. The concentrated cell samples were analyzed using a haemocytometer. Cell separation efficiency was calculated as the percentage of target parasite cells among all the parasite cells collected at that outlet. For parasite cell viability test, cells were flowed into the microchannels at different flow rates. The cells obtained from the outlets of the channel were immediately mixed with propidium iodide. Under fluorescence lighting, a number of the green and red stained cells are counted using a haemocytometer.

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