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The contamination of food and drinking water by bacteria that cause food poisoning is a critical public health issue. In general, the procedures for testing the presence of pathogenic bacteria in public is not very effective, because it is time consuming and does not facilitate real-time monitoring in a field setting. Therefore, this study introduced a fully automated platform that would allow non-experts to easily examine the major food poisoning bacteria in a field setting, from pretreatment samples to final detection. Two enterobacteria species, of four different bacteria species (i.e., Escherichia coli and Salmonella typhimurium) were successfully immobilized on the surface of magnetic beads by exploiting the specific binding force with mannose. Subsequently, magneto-electrochemical impedance measurement technology allowed bacterial detection with a high sensitivity. E. coli, typical enterobacteria, was detected in 25 min with a detection limit of 100 CFU/mL. Moreover, we demonstrated that the automatic performance and the experimental consistency was greatly improved in comparison with those of manually conducted experiments.

Salivary cortisol is frequently used as a biomarker of stress. However, no study has used salivary cortisol to evaluate stress levels related to personal characteristics with a paper-based lateral flow assay (LFA) strip and a smartphone holder, and a smartphone at the same time during simulated speech communication. In this paper, we investigated variations in levels of salivary cortisol, communication apprehension, and the effects of self-efficacy via the Smartphone Linked Stress Measurement (SLSM) that we have recently reported. Saliva samples were collected by 48 participants (30 male and 18 female) at three moments: immediately before public speaking (basal measurement), immediately after public speaking (speech measurement), and forty minutes after taking a rest (relaxed measurement). Results from the questionnaire showed that salivary cortisol levels, communication apprehension, and self-efficacy were significantly correlated. Also, anxiety about speaking can raise their stress levels during their speeches, as reflected in their increased cortisol levels. Therefore, this study establishes the effects of self-efficacy on communication apprehension and salivary cortisol.

This is a one-step POC biosensor that guarantees rapid assay times, low-cost analysis, simple handling, stability, and is easy to mass product. However, it has several drawbacks such as limited sample volume and relatively low sensitivity. To overcome these disadvantages, we have designed and fabricated the µ-PAD to confine fluid flow by creating a hydrophobic channel in the paper to improve the sensitivity. The channel pattern was drawn by a computer-aided design program and directly printed by a commercially available wax printer which generates the hydrophobic channel pattern. While maintaining a constant sample, absorption, and conjugation pad, the width of the detection pad was reduced from 5 mm to 2 mm at intervals of 1 mm. The intensity of bands from the single- and double-orifice patterns increased identically compared with the device with no orifice. The relative intensity of the signal bands increased from 141 to 158. Also, numerical simulation was performed to validate the experimental result by using lattice Boltzmann method. We observed that the sensitivity was enhanced at a specific detection pad width (3 mm). Therefore, our simple structural change of the channel led to improve the colorimetric intensity. Cortisol, which is a known stress biomarker, was used to validation the device, an enhanced signal was obtained indicating that our device can be used for the detection psychological stress in humans.

Posttraumatic stress disorder (PTSD) is an anxiety-related disorder that occurs after an exposure to an emotionally traumatic event, such as a life-threatening experience, and that persists with intrusive and distressing emotion-laden memories. It can trigger further mental health problems, such as depression, bipolar disorder, mania and so on. As a large population suffers from these complex diseases, its treatment results in massive secondary costs to society. Recent diagnosis and treatment of PTSD is based on relatively subjective assessments through diverse symptoms checklists, clinical histories, mental status exams, patient self-reports, and symptom duration. Biological markers have not been identified, and a biochip for PTSD has not yet been developed. In this paper, we briefly review potential biomarkers that could be used to determine the disease stage of PTSD, and we propose new applications of biochip technology with which PTSD could be precisely measured in real time using body fluids, such as blood, saliva, and urine. Microfabrication techniques have made it possible to construct nano/micron-scale sensing parts/chips to accommodate molecular linkers and capture the biomarkers for PTSD. These techniques provide new opportunities to diagnose PTSD in a precise manner.

Real-time detection and quantification of food-borne bacteria draws increasing interest for evaluation of food quality and safety. Since living cells invariably contain adenosine triphosphate (ATP), the detection of bacterial ATP presents a fascinating method to determine its presence in food. Care must be taken however, to remove food-derived extracellular ATP, which will interfere with detection by ATP-luminescence. We developed a microfluidic and dielectrophoretic (DEP) device for intracellular ATP detection, which captures microorganisms by DEP force and washes extracellular ATP away. The yield of capture by DEP force at a 10 μL∙min−1 flow rate used in experiments was 87.7%. At constant ATP level the electrical sensor responded in proportion to the bacterial concentration. With a constant bacterial concentration and varying ATP, the signal did not change. These results show that the device can remove the extracellular ATP contribution from food to be sampled.

In this article, we introduce a rapid and simple fabrication method to realize a 3-dimensional (3-D) microfluidic channel with a near-perfect circular cross section. This new concept of fabrication method is defined by metal wire removal process, where the metal wire such as a thin soldering wire for the 3-D circular shape is commercially available. For the microfluidic channel mold, PDMS (polydimethylsiloxane) was poured on several shapes such as 3-D circular, helix, and double helix shapes, of soldering wire and solidified. The soldering wire was then melted out by heating. With the two-step process, rapidly and simply fabricated 3-D circular microfluidic channels can be obtained. CPAE (endothelial cell line) cells were cultured inside the channel to evaluate the biocompatibility of the fabricated microfluidic channel. Our method will be very useful in making various circular shapes of 3-D microfluidic devices that need multi-depth and round corners inside the channel.

DNA marker information is used to identify or distinguish cattle breeds or individual animal. The purpose of this study was to apply Bovine Genotypes Kit Version 1.1/2.1 to bovine DNA samples (National Institute of Animal Science) taken from Australian / American beef (n=148), Holstein beef (n=170) and Hanwoo cattle (n=177) bred in Jeongeub, Jeonbuk, Korea, so that it could distinguish Hanwoo breed. The Bovine Genotype Kits consist of 16 ISAG MS markers, which were used to build a database of genotypes in each group. Genotyping results were analyzed using MS Tool kit and Phylip program to create phylogenetic tree. The GeneClass 2.0 was used to estimate breed identification. These analyses found that this kit had 100% capacity to distinguish Hanwoo beef, 95.3% capacity to differentiate Australian / American beef and 90% capacity to identify Korean Holstein steer beef. Hence, it is expected that 16 commercial microsatellite markers is useful to categorizegenetic characteristics of Hanwoo breed and also identify Hanwoo individuals and the origin of beef. In particular, it is expected that these markers will be advantageous in discriminating domestic Holstein beef from Australian / Americanbeef. (Key words : Hanwoo, Microsatellite, Individual identification, Geneclass analysis, Phylogenetic analysis)

Bacterial cells were patterned efficiently on a nutrient-coated membrane in a direct, rapid, and cost-effective manner using electro-hydrodynamically generated micro-droplets. By varying the viscosity and electrical conductivity of the bacterial printing solution, uniform droplets were obtained. Escherichia coli cells were directly printed onto a membrane filter, followed by overnight incubation on an agar plate which created line patterns of bacterial colonies with a width of approximately 160 μm. Optimization of the concentration of the chemical components [i.e. the ethylene glycol (EG), phosphate buffer (PB), and sodium chloride (NaCl)] in the processing bacterial solution allowed successful growth and patterning of the cells. The optimal conditions to achieve the most effective cell growth and patterning on these printed surfaces were an EG concentration of 40 vol% and a concentration as low as 10 mM of PB or NaCl in the printing solution. Cells passing through the electric nozzle during the printing process remained viable.

Various cell stimulation experiments have been traditionally conducted regarding observation of cells to specific stimulative factors, and in light of this area of study, we report a new method by utilizing micro-beads. HeLa cells and MC3T3 cells are cultured in straight PDMS (polydimethylsiloxane) microfluidic devices and are stimulated by sterilized polystyrene micro-beads. Cell culture medium either with or without micro-beads are introduced in microfluidic cell culturing chambers at a specific time interval, and stimulated cells are observed using an inverted microscope. The results show that cells exposed under micro-bead stimulation perform at a higher growth rate than those under normal conditions. This paper demonstrates that micro-beads can be used as a physical stimulation factor and affect cell growth behaviors.

This article presents a new design of a silicon-based microcalorimeter made with dual thermopiles and a microchannel. The dual thermopile was fabricated with chromium and copper using a microelectromechanical system (MEMS) technique, and the microchannel was made of PDMS using soft-lithography. Each thermopile consists of 26 thermocouple pairs and 50 μm wide electrodes. The total sensitivity of thermopile is 428 μV/K. The dual thermopile system enables the microcalorimeter to acquire reliable data in a rapid and convenient manner because it detects the reaction and reference temperatures simultaneously. This self-compensation allows our device to analyze a few microliters of sample solution without the need for a surrounding adiabatic vacuum.

A highly sensitive microfluidic device has been developed to separate apoptotic cells. Apoptotic Jurkat cells were selectively labeled with magnetic beads (0.8 microm diam) using the C2A protein which recognizes phosphatidylserine. The cell mixture was flowed through a microfluidic channel and apoptotic cells were separated by a 0.3 T permanent magnet. Separations using our device showed 96% agreement with those of a commercial flow cytometer, indicating our device can be used to sort apoptotic cells in a miniaturized system.