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Cells can respond and adapt to complex forms of environmental change. Budding yeast is widely used as a model system for these stress response studies. In these studies, the precise control of the environment with high temporal resolution is most important. However, there is a lack of single-cell research platforms that enable precise control of the temperature and form of cell growth. This has hindered our understanding of cellular coping strategies in the face of diverse forms of temperature change. Here, we developed a novel temperature-controlled microfluidic platform that integrates a microheater (using liquid metal) and a thermocouple (liquid metal vs. conductive PDMS) on a chip. Three forms of temperature changes (step, gradient, and periodical oscillations) were realized by automated equipment. The platform has the advantages of low cost and a simple fabrication process. Moreover, we investigated the nuclear entry and exit behaviors of the transcription factor Msn2 in yeast in response to heat stress (37 °C) with different heating modes. The feasibility of this temperature-controlled platform for studying the protein dynamic behavior of yeast cells was demonstrated. [ABSTRACT FROM AUTHOR]

The separation or purification of bacterial samples from a mixed cell suspension is critical in a variety of biomedical applications, such as sputum diagnostics and cell biology studies. We propose a streamline-based microfluidic filtration device for highly efficient purification of bacterial samples from a mixed cell suspension. The device is composed of tens of repeated streamline-based separation units that continuously filter the solution. By injecting a liquid sample such as liquefied human sputum solution through the device, approximately 50% of the injected sample solution can be collected from the filtration collection channels, which filter approximately 99.9% of the mammalian cells but retain approximately 60% to 90% of the bacteria. Different injection rates (0.2 ml h−1 to 30 ml h−1), different sample viscosities, and different initial bacterial densities were tested and confirmed that our separation method was robust. The easy operation, robustness and high efficiency indicate that our method may be useful for the separation or purification of bacterial samples from a mixed cell suspension, such as bacterial samples for sputum diagnostics. [ABSTRACT FROM AUTHOR]