In this paper, single cells adhesion force was measured using a nanofork. The nanofork was used to pick up a single cell on a line array substrate inside an environmental scanning electron microscope (ESEM). The line array substrate was used to provide small gaps between the single cells and the substrate. Therefore, the nanofork could be inserted through these gaps in order to successfully pick up a single cell. Adhesion force was measured during the cell pick-up process from the deflection of the cantilever beam. The nanofork was fabricated using focused ion beam (FIB) etching process while the line array substrate was fabricated using nanoimprinting technology. As to investigate the effect of contact area on the strength of the adhesion force, two sizes of gap distance of line array substrate were used, i.e., 1 μm and 2 μm. Results showed that cells attached on the 1 μm gap line array substrate required more force to be released as compared to the cells attached on the 1 μm gap line array substrate.
We employed dielectrophoresis to a yeast cell suspension containing amyloid-beta proteins (Aβ) in a microfluidic environment. The Aβ was separated from the cells and characterized using the gradual dissolution of Aβ as a function of the applied dielectrophoretic parameters. We established the gradual dissolution of Aβ under specific dielectrophoretic parameters. Further, Aβ in the fibril form at the tip of the electrode dissolved at high frequency. This was perhaps due to the conductivity of the suspending medium changing according to the frequency, which resulted in a higher temperature at the tips of the electrodes, and consequently in the breakdown of the hydrogen bonds. However, those shaped as spheroidal monomers experienced a delay in the Aβ fibril transformation process. Yeast cells exposed to relatively low temperatures at the base of the electrode did not experience a positive or negative change in viability. The DEP microfluidic platform incorporating the integrated microtip electrode array was able to selectively manipulate the yeast cells and dissolve the Aβ to a controlled extent. We demonstrate suitable dielectrophoretic parameters to induce such manipulation, which is highly relevant for Aβ-related colloidal microfluidic research and could be applied to Alzheimer's research in the future.
This paper describes the development of an integrated system using a dry film resistant (DFR) microfluidic channel consisting of pulsed field dielectrophoretic field-flow-fractionation (DEP-FFF) separation and optical detection. The prototype chip employs the pulse DEP-FFF concept to separate the cells (Escherichia coli and Saccharomyces cerevisiae) from a continuous flow, and the rate of release of the cells was measured. The separation experiments were conducted by changing the pulsing time over a pulsing time range of 2⁻24 s and a flow rate range of 1.2⁻9.6 μ L min - 1 . The frequency and voltage were set to a constant value of 1 M Hz and 14 V pk-pk, respectively. After cell sorting, the particles pass the optical fibre, and the incident light is scattered (or absorbed), thus, reducing the intensity of the transmitted light. The change in light level is measured by a spectrophotometer and recorded as an absorbance spectrum. The results revealed that, generally, the flow rate and pulsing time influenced the separation of E. coli and S. cerevisiae. It was found that E. coli had the highest rate of release, followed by S. cerevisiae. In this investigation, the developed integrated chip-in-a lab has enabled two microorganisms of different cell dielectric properties and particle size to be separated and subsequently detected using unique optical properties. Optimum separation between these two microorganisms could be obtained using a longer pulsing time of 12 s and a faster flow rate of 9.6 μ L min - 1 at a constant frequency, voltage, and a low conductivity.
Here we report for the first time that L-amino acid oxidase (LAAO), a major component of snake venom, induces apoptosis in yeast. The causative agent for induction of apoptosis has been shown to be hydrogen peroxide, produced by the enzymatic activity of LAAO. However, the addition of catalase, a specific hydrogen peroxide scavenger, does not prevent cell demise completely. Intriguingly, depletion of leucine from the medium by LAAO and the interaction of LAAO with yeast cells are shown to be the major factors responsible for cell demise in the presence of catalase.
Benefits of whole grains as dietary supplements and active ingredients in health products have been promoted. Despite being neglected as an agricultural byproduct of polished rice, pigmented rice bran has emerged as a promising source of natural anti-aging compounds. Indeed, the extract of red rice bran Hom Dang cultivar contained rich phenolic acids and flavonoids. It displayed high antioxidant activities in vitro and in vivo assays. Using yeast model, extract and bioactive compounds, quercetin and protocatechuic acid found in the rice bran pericarp, effectively reduced levels of intracellular reactive oxygen species (ROS), restored plasma membrane damages and prolonged life-span of pre-treated wild-yeast cells. Importantly, these molecules modulated life span-extension through a mechanism of ROS reduction that resembles to that operated under the highly conserved Tor1- and Sir2-dependent signaling pathways, with the human homologs TORC1 and SIRT1, respectively. The key longevity factors Sch9 and Rim15 kinases, Msn2/4 regulators and a novel transcription factor Asg1, the antioxidant enzymes superoxide dismutases and glutathione peroxidases played important role in mediating longevity. Yeast clearly provides an instrumental platform for rapid screening of compounds with anti-aging efficacies and advances knowledge in the molecular study of ageing.