Yeqing Sun

A Label-Free Microfluidic Biosensor for Activity Detection of Single Microalgae Cells Based on Chlorophyll Fluorescence

Detection of living microalgae cells is very important for ballast water treatment and analysis. Chlorophyll fluorescence is an indicator of photosynthetic activity and hence the living status of plant cells. In this paper, we developed a novel microfluidic biosensor system that can quickly and accurately detect the viability of single microalgae cells based on chlorophyll fluorescence. The system is composed of a laser diode as an excitation light source, a photodiode detector, a signal analysis circuit, and a microfluidic chip as a microalgae cell transportation platform. To demonstrate the utility of this system, six different living and dead algae samples (Karenia mikimotoi Hansen, Chlorella vulgaris, Nitzschia closterium, Platymonas subcordiformis, Pyramidomonas delicatula and Dunaliella salina) were tested. The developed biosensor can distinguish clearly between the living microalgae cells and the dead microalgae cells. The smallest microalgae cells that can be detected by using this biosensor are 3 μm ones. Even smaller microalgae cells could be detected by increasing the excitation light power. The developed microfluidic biosensor has great potential for in situ ballast water analysis.

Automatic particle detection and sorting in an electrokinetic microfluidic chip

This paper reports a lab‐on‐a‐chip device that can automatically detect and sort particles based on their size differences with a high resolution. The PDMS‐glass microfluidic chip is made by soft‐lithography technique. A differential resistive pulse sensor is employed to electrically detect the sizes of the particles in EOF generated by applying DC voltages across channels. The detected resistive pulse sensor signals, whose amplitudes are proportional to particles’ sizes, will automatically trigger the sorting process that is controlled by applying a voltage pulse (36 V) whenever a target particle is detected. This method was applied to automatically detect and sort polystyrene particles and microalgae in aqueous solutions. Sorting 5 μm polymer particle from a mixture of 4‐ and 5‐μm polystyrene particles in aqueous solution, i.e. 1 μm sorting resolution, was demonstrated. The device described in this paper is simple, automatic, and label‐free with high sorting resolution. It has wide applications in sample pretreatment and target particles detection.

DC dielectrophoresis separation of marine algae and particles in a microfluidic chip

This paper reports a microfluidic method of continuous separation of marine algae and particles by DC dielectrophoresis. The locally non-uniform electric field is generated by an insulating PDMS triangle hurdle fabricated within a PDMS microchannel. Both the particles and algae are subject to negative DEP forces at the hurdle where the gradient of local electric-field strength is the strongest. The DEP force acting on the particle or the algae depends on particles’ or algae’s volume, shape and dielectric properties. Thus the moving particles and algae will be repelled to different streamlines when passing the hurdle. In this way, combined with the electroosmotic flow, continuous separation of algae of two different sizes, and continuous separation of polystyrene particles and algae with similar volume but different shape were achieved. This first demonstration of DC DEP separation of polystyrene particles and algae with similar sizes illustrates the great influence of dielectric properties on particle separation and potentials for sample pretreatment.

Inhibition of cell growth and induction of inflammation by endosulfan in HUVEC-C cells

Endosulfan is one of the organochlorine pesticides. It has been associated with a wide range of adverse health effects. However, it is unknown whether endosulfan causes endothelial dysfunction. In the present study, we investigated the effects of endosulfan on human vascular endothelial cells. We exposed human umbilical vein endothelial cells (HUVEC‐C) to varying concentrations of endosulfan for 48 h. The results showed that endosulfan lowered cell viability and inhibited cell proliferation in a dose‐dependent manner. Flow cytometric analysis showed that endosulfan at 60 μM induced G1 cell cycle arrest, a response attributed to down‐regulation of CDK6 and pRb dephosphorylation. We observed that endosulfan at 40 and 60 μM induced a considerable percentage of cells to undergo apoptosis, as detected by Annexin‐V binding assays. Endosulfan reduced mitochondrial transmembrane potential, leading to the release of cytochrome c into the cytoplasm; meanwhile, endosulfan also inhibited the mRNA expression level of survivin, which resulted in the activation of caspase‐3. These results indicated that the intrinsic mitochondria‐mediated pathway was involved in apoptotic process. Exposure to endosulfan increased the secretion and mRNA expression levels of inflammation factors interleukin (IL)−6 and IL‐8, suggesting that endosulfan could cause inflammation. Overall, these findings suggested that endosulfan is toxic to HUVEC‐C cells, resulting in endothelial dysfunction.

Effects of microgravity on DNA damage response in Caenorhabditis elegans during Shenzhou-8 spaceflight

Abstract Purpose: Space radiations and microgravity both could cause DNA damage in cells, but the effects of microgravity on DNA damage response to space radiations are still controversial. Materials and methods: A mRNA microarray and microRNA micro- array in dauer larvae of Caenorhabditis elegans (C. elegans) that endured spaceflight environment and space radiations environment during 16.5-day Shenzhou-8 space mission was performed. Results: Twice as many transcripts significantly altered in the spaceflight environment than space radiations alone. The majority of alterations were related to protein amino acid dephosphorylation and histidine metabolic and catabolic processes. From about 900 genes related to DNA damage response, 38 differentially expressed genes were extracted; most of them differentially expressed under spaceflight environment but not space radiations, although the identical directions of alteration were observed in both cases. cel-miR-81, cel- miR-82, cel-miR-124 and cel-miR-795 were predicted to regulate DNA damage response through four different anti-correlated genes. Conclusions: Evidence was provided that, in the presence of space radiations, microgravity probably enhanced the DNA damage response in C. elegans by integrating the transcriptome and microRNome.

A new hand-held microfluidic cytometer for evaluating irradiation damage by analysis of the damaged cells distribution

Space radiation brings uneven damages to cells. The detection of the distribution of cell damage plays a very important role in radiation medicine and the related research. In this paper, a new hand-held microfluidic flow cytometer was developed to evaluate the degree of radiation damage of cells. The device we propose overcomes the shortcomings (e.g., large volume and high cost) of commercial flow cytometers and can evaluate the radiation damage of cells accurately and quickly with potential for onsite applications. The distribution of radiation-damaged cells is analyzed by a simultaneous detection of immunofluorescence intensity of γ-H2AX and resistance pulse sensor (RPS) signal. The γ-H2AX fluorescence intensity provides information of the degree of radiation damage in cells. The ratio of the number of cells with γ-H2AX fluorescence signals to the total numbers of cells detected by RPS indicates the percentage of the cells that are damaged by radiation. The comparison experiment between the developed hand-held microfluidic flow cytometer and a commercial confocal microscope indicates a consistent and comparable detection performance.

An induced current method for measuring zeta potential of electrolyte solution–air interface

This paper reports a novel and very simple method for measuring the zeta potential of electrolyte solution-air interface. When a measuring electrode contacts the electrolyte solution-air interface, an electrical current will be generated due to the potential difference between the electrode-air surface and the electrolyte solution-air interface. The amplitude of the measured electric signal is linearly proportional to this potential difference; and depends only on the zeta potential at the electrolyte solution-air interface, regardless of the types and concentrations of the electrolyte. A correlation between the zeta potential and the measured voltage signal is obtained based on the experimental data. Using this equation, the zeta potential of any electrolyte solution-air interface can be evaluated quickly and easily by inserting an electrode through the electrolyte solution-air interface and measuring the electrical signal amplitude. This method was verified by comparing the obtained results of NaCl, MgCl2 and CaCl2 solutions of different pH values and concentrations with the zeta potential data reported in the published journal papers.

ALGAE DETECTION AND SHIP'S BALLAST WATER ANALYSIS BY A MICROFLUIDIC LAB-ON-CHIP DEVICE

This article reports a microfluidic lab-on-chip device that can detect algae and analyze ships ballast water treatment performance according to the standard set by the International Convention for the Control and Management of Ships’ Ballast Water and Sediments. A microfluidic differential resistive pulse sensor (RPS) was employed to detect, count, and size two algae of different sizes, a larger alga, Pseudokirchneriella subcapitata, and a smaller one, Chlorella vulgaris. The number rate of the algae flowing through the sensing gate per 2 min is a linear function of the sample concentration. A number rate-concentration correlation curve was experimentally obtained and verified, and can be used to determine the algae concentration simply by counting the number of peaks within several minutes. This lab-on-chip device described in this article is sensitive enough to detect the algae killing efficiency by electrolysis treatment to the ballast water. Also, this device can be easily operated by nonprofessionals and thus has great potentials in shipboard on-site testing for port state control.

MicroRNAs Act as Potential Regulators in Apoptosis and Senescence Against Carcinogenicity Induced by Environmental Pollutants

Environmental pollution is a growing public health concern worldwide and adverse pollutants are associated with a variety of cancers. microRNAs (miRNAs), a class of small non-coding RNAs, act as powerful and sensitive posttranscriptional regulators of gene expression. Recent reports demonstrate that miRNAs play important roles in apoptosis and senescence, both of which are regarded as protective mechanisms against the carcinogenesis. Here, we will give an overview on the expression profile and regulatory role of miRNA in response to environmental pollution. This review will provide better understanding of the potential of miRNAs as novel biomarkers and therapeutic targets for human cancers caused by environmental pollutants.