FTIR imaging detects diet and genotype-dependent chemical composition changes in wild type and mutant C. elegans strains.

This study focuses on the use of Fourier Transform Infrared (FTIR) microspectroscopy to determine chemical changes induced in the nematode Caenorhabditis elegans by supplementation of C. elegans maintenance media (CeMM) by Eicosapentaenoic acid (EPA). Wild-type C. elegans (N2) and mutant strains (tub-1 and fat-3) were grown in CeMM alone, and CeMM supplemented with EPA at 25 or 100 µM. Feeding was performed for 72 h. FTIR imaging was performed in transmission mode on individual worms. The FTIR imaging analysis of wild-type animals revealed the presence of vibrations assigned to unsaturated fatty acids, specifically bands at 3008 cm-1 ([double bond, length as m-dash]C-H, olefinic stretch) and 1744 cm-1 (C[double bond, length as m-dash]O, unsaturated fatty acids). It confirmed previously reported synthesis of unsaturated fatty acids in wild-type C. elegans. For the FTIR spectra of mutant strains, these vibrations were absent or present only as very small shoulder, which indicates that tub-1 and fat-3 synthesize essentially saturated fatty acids as indicated by the presence of -CH2 and C[double bond, length as m-dash]O vibrations. These results are in agreement with previous studies which reported that these mutants have altered lipid compositions. Principal component analysis showed differences in chemical composition between wild-type and mutant strains as well as between mutant strains cultured in normal CeMM and those cultured in CeMM supplemented with EPA. This study demonstrated the usefulness of FTIR microspectroscopy to investigate fat metabolism in C. elegans.

Probing the mechanical properties of brain cancer cells using a microfluidic cell squeezer device.

Despite being invasive within surrounding brain tissues and the central nervous system, little is known about the mechanical properties of brain tumor cells in comparison with benign cells. Here, we present the first measurements of the peak pressure drop due to the passage of benign and cancerous brain cells through confined microchannels in a "microfluidic cell squeezer" device, as well as the elongation, speed, and entry time of the cells in confined channels. We find that cancerous and benign brain cells cannot be differentiated based on speeds or elongation. We have found that the entry time into a narrow constriction is a more sensitive indicator of the differences between malignant and healthy glial cells than pressure drops. Importantly, we also find that brain tumor cells take a longer time to squeeze through a constriction and migrate more slowly than benign cells in two dimensional wound healing assays. Based on these observations, we arrive at the surprising conclusion that the prevailing notion of extraneural cancer cells being more mechanically compliant than benign cells may not apply to brain cancer cells.

Electrowetting --a versatile tool for controlling microdrop generation.

Integrating insulator-covered electrodes into a microfluidic flow focusing device (FFD) we demonstrate enhanced flexibility and control of the flow of two non-miscible liquids based on electrowetting (EW). In the parameters space, determined by liquid inlet pressures, we identify a specific region where drops can only be generated and addressed via EW. In this regime we show that the size distribution and the frequency of drop generation can be controlled by the applied voltage and the width of voltage pulses. Moreover it turns out that with EW the drop size and the frequency can be tuned independently. Finally we show that the same drop generation phenomena can also be observed in the presence of surfactants.