Simon Song

A Thermoresponsive Fluorogenic Conjugated Polymer for a Temperature Sensor in Microfluidic Devices

A new, microfluidic temperature sensor system, based on a thermoresponsive conjugated polymer supramolecule, has been developed. By generating blue-phase polydiacetylene (PDA) sensor droplets using hydrodynamic instability, we were able to monitor the variation of fluorescent intensity of the droplets with respect to the flow temperature.

Phylogenetic and phylogeographic relationships in Ixodes holocyclus and Ixodes cornuatus (Acari: Ixodidae) inferred from COX1 and ITS2 sequences

We inferred the phylogenetic and phylogeographic relationships in ticks, which were identified morphologically as Ixodes holocyclus and Ixodes cornuatus, from mitochondrial cytochrome oxidase subunit 1 (COX1) and nuclear internal transcribed spacer 2 (ITS2) sequences. We obtained COX1 (640bp) and ITS2 (527-568bp) sequences from 429 ticks from 49 localities in Tasmania, Victoria, New South Wales and Queensland, Australia. Our analyses show that there are two species of Ixodes in eastern Australia that cause paralysis in dogs and other mammals: I. holocyclus and I. cornuatus. Further, we conclude that the morphological criteria used to differentiate female I. holocyclus and I. cornuatus are equivocal but I. holocyclus can be distinguished from I. cornuatus using COX1 and/or ITS2 sequences. Intraspecific genetic variation in I. holocyclus and I. cornuatus was less than 0.86% and 0.19% for COX1 and ITS2, respectively. Ixodes holocyclus could be genetically distinguished between different geographic ranges. There were no significant genetic differences between I.cornuatus from Tasmania and mainland Australia, but there are some COX1 haplotypes of I. cornuatus from the mainland that were not detected in Tasmanian and vice versa.

Hierarchical and Multifunctional Three‐Dimensional Network of Carbon Nanotubes for Microfluidic Applications

Three-Dimensional network of carbon nanotubes: The 3D network of CNTs have hierarchical structures comprised of interconnected SWNTs between Si pillars in microfluidic channels. The Al(2)O(3) coated 3D networks were used for size different nanoparticles filtration and streptavidin capturing in very diluted solution. The 3D network of SWNTs systems will provide a robust multifuncitonal platform for a variety of biomedical and environmental applications.

Gas/liquid sensing via chemotaxis of Euglena cells confined in an isolated micro-aquarium

We demonstrate on-chip gas/liquid sensing by using the chemotaxis of live bacteria (Euglena gracilis) confined in an isolated micro-aquarium, and gas/liquid permeation through porous polydimethylsiloxane (PDMS). The sensing chip consisted of one closed micro-aquarium and two separated bypass microchannels along the perimeter of the micro-aquarium. Test gas/liquid and reference samples were introduced into the two individual microchannels separately, and the gas/liquid permeated through the PDMS walls and dissolved in the micro-aquarium water, resulting in a chemical concentration gradient in the micro-aquarium. By employing the closed micro-aquarium isolated from sample flows, we succeeded in measuring the chemotaxis of Euglena for a gas substance quantitatively, which cannot be achieved with the conventional flow-type or hydro-gel-type microfluidic devices. We found positive (negative) chemotaxis for CO2 concentrations below (above) 15%, with 64 ppm as the minimum concentration affecting the cells. We also observed chemotaxis for ethanol and H2O2. By supplying culture medium via the microchannels, the Euglena culture remained alive for more than 2 months. The sensing chip is thus useful for culturing cells and using them for environmental toxicity/nutrition studies by monitoring their motion.

Two-dimensional optical feedback control of Euglena confined in closed-type microfluidic channels

We examined two-dimensional (2D) optical feedback control of phototaxis flagellate Euglena cells confined in closed-type microfluidic channels (microaquariums), and demonstrated that the 2D optical feedback enables the control of the density and position of Euglena cells in microaquariums externally, flexibly, and dynamically. Using three types of feedback algorithms, the density of Euglena cells in a specified area can be controlled arbitrarily and dynamically, and more than 70% of the cells can be concentrated into a specified area. Separation of photo-sensitive/insensitive Euglena cells was also demonstrated. Moreover, Euglena-based neuro-computing has been achieved, where 16 imaginary neurons were defined as Euglena-activity levels in 16 individual areas in microaquariums. The study proves that 2D optical feedback control of photoreactive flagellate microbes is promising for microbial biology studies as well as applications such as microbe-based particle transportation in microfluidic channels or separation of photo-sensitive/insensitive microbes.

Size-controlled fabrication of polydiacetylene-embedded microfibers on a microfluidic chip.

A microfluidic technique was employed to fabricate polydiacetylene (PDA)-embedded hydrogel microfibers. By taking advantage of calcium ion-induced insoluble hydrogel formation, supramolecularly assembled diacetylene (DA)-surfactant complexes were successfully immobilized in the calcium alginate fibers. Thus, instantaneous microfiber formation was observed when the core flow of DA supramolecules-containing alginate solution met the sheath flow of calcium ions. UV irradiation of the resulting fibers afforded blue colored PDAs, and the formation of a conjugated polymer was confirmed by heat-induced phase transition and by Raman spectroscopy. By adjusting the core and sheath flow rates, PDA-embedded hydrogel fibers of various sizes were obtained.

Fragmented mitochondrial genomes of the rat lice, Polyplax asiatica and Polyplax spinulosa: intra-genus variation in fragmentation pattern and a possible link between the extent of fragmentation and the length of life cycle

BackgroundBlood-sucking lice (suborder Anoplura) parasitize eutherian mammals with 67% of the 540 described species found on rodents. The five species of blood-sucking lice that infest humans and pigs have fragmented mitochondrial genomes and differ substantially in the extent of fragmentation. To understand whether, or not, any life-history factors are linked to such variation, we sequenced the mt genomes of Polyplax asiatica and Polyplax spinulosa, collected from the greater bandicoot rat, Bandicota indica, and the Asian house rat, Rattus tanezumi, respectively.ResultsWe identified all of the 37 mitochondrial genes common to animals in Polyplax asiatica and Polyplax spinulosa. The mitochondrial genes of these two rat lice are on 11 circular minichromosomes; each minichromosome is 2–4 kb long and has 2–7 genes. The two rat lice share the same pattern for the distribution of the protein-coding genes and ribosomal RNA genes over the minichromosomes, but differ in the pattern for the distribution of 8 of the 22 transfer RNA genes. The mitochondrial genomes of the Polyplax rat lice have 3.4 genes, on average, on each minichromosome and, thus, are less fragmented than those of the human lice (2.1 and 2.4 genes per minichromosome), but are more fragmented than those of the pig lice (4.1 genes per minichromosome).ConclusionsOur results revealed distinct patterns of mitochondrial genome fragmentation within the genus Polyplax and, furthermore, indicated a possible inverse link between the extent of mitochondrial genome fragmentation and the length of life cycle of the blood-sucking lice.

Euglena-based neurocomputing with two-dimensional optical feedback on swimming cells in micro-aquariums

We report on neurocomputing performed with real Euglena cells confined in micro-aquariums, on which two-dimensional optical feedback is applied using the Hopfield-Tank algorithm. Trace momentum, an index of swimming activity of Euglena cells, is used as the input/output signal for neurons in the neurocomputation. Feedback as blue-light illumination results in temporal changes in trace momentum according to the photophobic reactions of Euglena. Combinatorial optimization for a four-city traveling salesman problem is achieved with a high occupation ratio of the best solutions. Two characteristics of Euglena-based neurocomputing desirable for combinatorial optimization are elucidated: (1) attaining one of the best solutions to the problem, and (2) searching for a number of solutions via dynamic transition between the best solutions. Mechanisms responsible for the two characteristics are analyzed in terms of network energy, photoreaction ratio, and dynamics/statistics of Euglena movements. The spontaneous fluctuation in input/output signals and reduction in photoreaction ratio were found to be key factors in producing characteristic (1), while the photo-insensitive Euglena cells or the accidental evacuation of cells from non-illuminated areas causes characteristic (2). Furthermore, we show that the photophobic reactions of Euglena involves various survival strategies such as adaptation to blue-light or awakening from dormancy, which can extend the performance of Euglena-based neurocomputing toward deadlock avoidance or program-less adaptation. Finally, two approaches for achieving a high-speed Euglena-inspired Si-based computation are described.

Fragmented mitochondrial genomes in two suborders of parasitic lice of eutherian mammals (Anoplura and Rhynchophthirina, Insecta).

Parasitic lice (order Phthiraptera) infest birds and mammals. The typical animal mitochondrial (mt) genome organization, which consists of a single chromosome with 37 genes, was found in chewing lice in the suborders Amblycera and Ischnocera. The sucking lice (suborder Anoplura) known, however, have fragmented mt genomes with 9–20 minichromosomes. We sequenced the mt genome of the elephant louse, Haematomyzus elephantis – the first species of chewing lice investigated from the suborder Rhynchophthirina. We identified 33 mt genes in the elephant louse, which were on 10 minichromosomes. Each minichromosome is 3.5–4.2 kb in size and has 2–6 genes. Phylogenetic analyses of mt genome sequences confirm that the elephant louse is more closely related to sucking lice than to the chewing lice in the Amblycera and Ischnocera. Our results indicate that mt genome fragmentation is shared by the suborders Anoplura and Rhynchophthirina. Nine of the 10 mt minichromosomes of the elephant louse differ from those of the sucking lice (Anoplura) known in gene content and gene arrangement, indicating that distinct mt karyotypes have evolved in Anoplura and Rhynchophthirina since they diverged ~92 million years ago.

A one-step photolithography method for fabrication of a staggered herringbone mixer using inclined UV lithography

We present a facile method for fabrication of a staggered herringbone mixer using inclined UV lithography, in which the incident UV angle is not perpendicular to the wafer. With this fabrication method, we were able to fabricate staggered herringbone ridges and microchannels simultaneously. As a result, complicated photolithography processes were reduced to a single step. Herein, we describe the fabrication method and performance of the resulting mixers in detail, including the effects of ridge height on mixing. This fabrication technique can be applied directly to the fabrication of other 3D structures on microfluidic chips.