Browsing by Author "Cheng, J.-Y."

© 2015 AIP Publishing LLC. Cell migration is an essential process involved in the development and maintenance of multicellular organisms. Electric fields (EFs) are one of the many physical and chemical factors known to affect cell migration, a phenomenon termed electrotaxis or galvanotaxis. In this paper, a microfluidics chip was developed to study the migration of cells under different electrical and chemical stimuli. This chip is capable of providing four different strengths of EFs in combination with two different chemicals via one simple set of agar salt bridges and Ag/AgCl electrodes. NIH 3T3 fibroblasts were seeded inside this chip to study their migration and reactive oxygen species (ROS) production in response to different EF strengths and the presence of β-lapachone. We found that both the EF and β-lapachone level increased the cell migration rate and the production of ROS in an EF-strength-dependent manner. A strong linear correlation between the cell migration rate and the amount of intracellular ROS suggests that ROS are an intermediate product by which EF and β-lapachone enhance cell migration. Moreover, an anti-oxidant, α-tocopherol, was found to quench the production of ROS, resulting in a decrease in the migration rate.

We present a dielectrophoresis (DEP)-based cellular microarray chip for cell-based anticancer drug screening in perfusion microenvironments. Human breast cancer cells, MCF7, were seeded into the chip and patterned via DEP forces onto the planar interdigitated ring electrode (PIRE) arrays. Roughly, only one third of the cell amount was required for the chip compared to that for a 96-well plate control. Drug concentrations (cisplatin or docetaxel) were stably generated by functional integration of a concentration gradient generator (CGG) and an anti-crosstalk valve (ACV) to treat cells for 24 hours. Cell viability was quantified using a dual staining method. Results of cell patterning show substantial uniformity of patterned cells (92 ± 5 cells per PIRE). Furthermore, after 24 hour drug perfusion, no statistical significance in dose-responses between the chip and the 96-well plate controls was found. The IC50 value from the chip also concurred with the values from the literature. Moreover, the perfusion culture exhibited reproducibility of drug responses of cells on different PIREs in the same chamber. The chip would enable applications where cells are of limited supply, and supplement microfluidic perfusion cultures for clinical practices. ? 2011 The Royal Society of Chemistry.

The morphologic changes of living cells under drug interactions were studied by using 80-nm gold nanoparticles and dark-field optical section microscopy. The gold nanoparticles were coated with poly (L-lysine), which attached to the membranes of various cells by way of electrostatic attractive force. A three-dimensional (3-D) morphological image was obtained by measuring the peak scattering intensities of gold nanoparticles at different focal planes. An algorithm for the reconstruction of 3-D cell morphology was presented. With the measured nanoparticle images and calculations, we show morphologic changes of lung cancer cells under the interaction of cytochalasin D drug at different times. ? 2009 Society of Photo-Optical Instrumentation Engineers.

Uniform patterning of cells is highly desirable for most cellular studies involving cell-cell interactions but is often difficult in an in vitro environment. This paper presents the development of a collagen-coated planar interdigitated ring electrode (PIRE) array utilizing positive dielectrophoresis to pattern cells uniformly. Key features of the PIRE design include: (1) maximizing length along the edges where the localized maximum in the electric field exists; (2) making the inner gap slightly smaller than the outer gap in causing the electric field strength near the center of a PIRE being generally stronger than that near the outer edge of the same PIRE. Results of human hepatocellular carcinoma cells, HepG2, adhered on a 6 × 6 PIRE array show that cells patterned within minutes with good uniformity (48 ± 6 cells per PIRE). Cell viability test revealed healthy patterned cells after 24 h that were still confined to the collagen-coated PIREs. Furthermore, quantification of fluorescence intensity of living cells shows an acceptable reproducibility of cell viability among PIREs (mean normalized intensity per PIRE was 1 ± 0.138). The results suggest that the PIRE array would benefit applications that desire uniform cellular patterning, and improve both response and reproducibility of cell-based biosensors. ? 2008 Elsevier B.V. All rights reserved.