No abstract

Maintaining cell viability within 3D tissue engineering scaffolds is an essential step toward a functional tissue or organ. Assessment of cell viability in 3D scaffolds is necessary to control and optimize tissue culture process. Monitoring systems based on respiration activity of cells (e.g., oxygen consumption) have been used in various cell cultures. In this research, an online monitoring system based on respiration activity was developed to monitor cell viability within acellular lung scaffolds. First, acellular lung scaffolds were recellularized with human umbilical cord vein endothelial cells, and then, cell viability was monitored during a 5-day period. The real-time monitoring system generated a cell growth profile representing invaluable information on cell viability and proliferative states during the culture period. The cell growth profile obtained by the monitoring system was consistent with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide analysis and glucose consumption measurement. This system provided a means for noninvasive, real-time, and repetitive investigation of cell viability. Also, we showed the applicability of this monitoring system by introducing shaking as an operating parameter in a long-term culture.

A dip-and-read microfluidic paper-based analytical device (µPAD) was developed for the qualitative and quantitative detection of the total hardness of water. To create well-defined hydrophobic barriers on filter paper, a regular office printer and a commercially available permanent marker pen were utilized as a quick and simple technique with easily accessible equipment/materials to fabricate µPAD in new or resource-limited laboratories without sophisticated equipment. After a wettability and barrier efficiency analysis on the permanent marker colors, the blue and green ink markers exhibited favorable hydrophobic properties and were utilized in the fabrication of the developed test devices. The device had five reaction and detection zones modeled after the classification given by the World Health Organization (WHO), so qualitatively it determined whether the water was ‘soft’, ‘moderately hard’, ‘hard’, or ‘very hard’ by changing color from blue to pink in about 3 min. The device was also used to introduce an alternative colorimetric reaction for quantitative analysis of the water hardness without the need for ethylenediaminetetraacetic acid (EDTA) and without compromising the simplicity and low cost of the device. The developed µPAD showed a calculated limit of detection (LOD) of 0.02 mM, which is at least 80% less than those of commercially available test strips and other reported µPADs, and the results of the real-world samples were consistent with those of the standard titration (with EDTA). In addition, the device exhibited stability for 2 months at room and frigid condition (4 °C) and at varying harsh temperatures from 25 to 100 °C. The results demonstrate that the developed paper-based device can be used for rapid, on-site analysis of water with no interferences and no need for a pipette for sample introduction during testing.