Summary Microfluidic dielectrophoresis (DEP) technology has been applied to many devices to perform label-free target cell separation. Cells separated by these devices are used in laboratories, mainly for medical research. The present study designed a microfluidic DEP device to fabricate a rapid and semiautomated cell separation system in conjunction with microscopy to enumerate the separated cells. With this device, we efficiently segregated bacterial cells from liquid products and enriched one cell type from two mixed eukaryotic cell types. The device eliminated sample pretreatment and established cell separation by all-in-one operation in a lab-on-chip, requiring only a small sample volume (0.5–1 mL) to enumerate the target cells and completing the entire separation process within 30 min. Such a rapid cell separation technique is in high demand by many researchers to promptly characterize the target cells.
Cell separation technique is essential for the detection of circulating tumor cells in blood and for enrichment of stem cell in regenerative medicine. However, conventional methods require cell labeling such as antibodies, which may damage the cells during the operation. Therefore, dielectrophoresis (DEP), a “label‐free” separation technique that eliminates the effects on cells, has been attracting attention. In this paper, we investigated the dielectric properties of Jurkat cells derived from human T‐cell leukemia cells by dielectrophoretic velocimetry. An equivalent circuit model of the cell was constructed and the frequency characteristics of the voltage of each layer of the cell were calculated. As a result, it was shown that the live and dead cells showed opposite dielectrophoretic forces in the region below 10 kHz, indicating the possibility of separating them. The agreement between the theoretical calculations and the experimental results shows the validity of the equivalent circuit model.
The aim of this study is to clarify factors that support the work engagement of nurses, who bear the burden of extended day shifts, by focusing on the advantages of the variable shift system and workday break activities. Methods: Nurses who were working under a variable shift system were asked to complete a self-report questionnaire to examine the workload, work engagement, work stressors, stress-coping strategies, and stress-coping break time activities, as well as the advantages and disadvantages of the variable shift system. Nine break activities were classified into the following four categories: social activities, rest/relaxation, entertainment, and cognitive activities. The advantages or disadvantages of the variable shift system were scored by developing composite variables using principal component analysis. These variables were used to perform a multiple regression analysis with work engagement as the dependent variable. Results: The advantage score was the variable most strongly correlated with work engagement. In contrast, "Quantitative workload" was negatively correlated with work engagement. Among break activities, in the social activities category correlations were observed in "Both conversation and Email/SNS" and "Conversation only". Although in fact most nurses chose conversation as one of the break options, more than half of the nurses selected rest/relaxation as their ideal break activity. Conclusion: Our study suggested that the variable shift system supported the work engagement of nurses who worked extended day shifts. The results also suggested that it would be useful to arrange the employee lounge environment so that employees could freely choose between "conversation" or "taking a rest" depending on the circumstances.
Background PixeeMo™ is a compact instrument that enables bacterial cell counting using microfluidic chips instead of counting of colonies on culture media. Chips containing electrodes, based on “fluid, electric filtering and sorting technology (FES)”, allow the selection of bacterial cells from other components in the sample. In the United States (US), surface water or ground water affected by surface water must be treated to reduce the total microbial load to less than 500 CFU/mL. In Japan, drinking water regulations limit the total bacterial load to 100 CFU/mL. Objective To validate the PixeeMo™ aerobic bacteria method based on the Japanese regulation in the range of 30-300 CFU/mL in drinking water. Methods PixeeMo™ aerobic bacteria method was compared to the Standard Methods for the Examination of Water and Wastewater (SMEWW) Method 9215B (2017) using naturally contaminated drinking water. Results The maximum repeatability standard deviation of the PixeeMo™ method was 14.8%. The difference of mean log10 values between the PixeeMo™ and SMEWW 9215B method ranged from -0.015 to 0.258. Similar results were obtained in the independent laboratory study. Conclusions PixeeMo™ method is equivalent to that of the SMEWW 9215B methods. The product consistency and stability study demonstrated no significant difference within the expiration date. The robustness study confirmed that there was no effect within the expected range. The Instrument variation study also demonstrated no significant difference among the data of 3 PixeeMo™ instruments. Highlights Total counts of bacteria in drinking water can be determined accurately within 1 h with the PixeeMo™.
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