Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Noritada Kaji Last modified date:2019.06.13

Professor / Department of Applied Chemistry / Faculty of Engineering


Papers
1. Taisuke Shimada, Hirotoshi Yasaki, Takao Yasui, Takeshi Yanagida, Noritada Kaji, Masaki Kanai, Kazuki Nagashima, Tomoji Kawai, Yoshinobu Baba, PM2.5 Particle detection in a microfluidic device by using ionic current sensing, Analytical Sciences, 10.2116/analsci.18C018, 34, 12, 1347-1349, 2018.01, We have demonstrated a PM2.5 analysis method that adds information on the number concentration and size by using microfluidic-based ionic current sensing with a bridge circuit. The bridge circuit allows for suppression of the background current and the detection of small PM2.5 particles, even if a relatively large micropore is used. This is the first demonstration of the detection of PM2.5 particles via ionic current sensing; our method enables analyses of both the number concentration and size..
2. Abdallah M. Zeid, Noritada Kaji, Jenny Jeehan M. Nasr, Fathalla Belal, Mohamed I. Walash, Yoshinobu Baba, Determination of baclofen and vigabatrin by microchip electrophoresis with fluorescence detection
Application of field-enhanced sample stacking and dynamic pH junction, New Journal of Chemistry, 10.1039/c8nj00829a, 42, 12, 9965-9974, 2018.01, A simple, rapid and sensitive microchip electrophoretic (MCE) method with fluorescence detection is described for the simultaneous determination of two GABA analogue drugs, baclofen (BCN) and vigabatrin (VGN). Pre-microchip derivatization of both analytes with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) was performed in a basic borate buffer. The NBD-fluorescent derivatives of the studied drugs (λex/em 470/540) were baseline separated in a dynamically-coated poly(methyl methacrylate) microfluidic channel within 120 s using a 40 mM borate buffer containing 0.4% methylcellulose as the background solution. The ability of methylcellulose to form a network sieve of small pore size allowed the labelled analytes to be separated efficiently according to their molecular size variations with a resolution factor equal to 7.8 and a number of theoretical plates of more than 50 0000 per meter. The MCE method was applied to assay BCN and VGN in tablets using 6-aminohexanoic acid as an internal standard. The method sensitivity was enhanced by application of combined stacking and a dynamic pH junction. The method was applied to assay BCN in human plasma and human urine samples with a detection limit lower than 0.3 ng mL-1 and mean extraction recoveries of more than 95% (% RSD < 7) after protein precipitation with methanol..
3. Taisuke Shimada, Takao Yasui, Asami Yokoyama, Tatsuro Goda, Mitsuo Hara, Takeshi Yanagida, Noritada Kaji, Masaki Kanai, Kazuki Nagashima, Yuji Miyahara, Tomoji Kawai, Yoshinobu Baba, Biomolecular recognition on nanowire surfaces modified by the self-assembled monolayer, Lab on a Chip, 10.1039/c8lc00438b, 18, 21, 3225-3229, 2018.01, Molecular recognition is one of the key factors in designing biosensors due to which nanowires functionalized with molecular recognition have attracted a lot of attention as promising candidates for nanostructures embedded in biosensors. However, the difficulty in real-world applications with analytical specificity is that molecular recognition on nanowires mainly depends on antibody modification with multistep modification procedures. Furthermore, the antibody modification suffers from nonspecific adsorption of undesired proteins in body fluid on the nanowires, which causes false responses and lowers sensitivity. Herein, we propose biomolecular recognition using surface-modified nanowires via thiolated 2-methacryloxyethyl phosphorylcholine (MPC-SH). MPC-SH enables self-assembled monolayer (SAM) modification, which contributes to the reduction of nonspecific adsorption of biomolecules onto the nanowires, and the specific capture of a target protein is attained in the presence of calcium ions. Our concept demonstrates the recognition of the biomarker protein on nanowire surfaces modified by MPC-SH SAM with a single step modification procedure..
4. Takao Yasui, Takeshi Yanagida, Taisuke Shimada, Kohei Otsuka, Masaki Takeuchi, Kazuki Nagashima, Sakon Rahong, Toyohiro Naito, Daiki Takeshita, Akihiro Yonese, Ryo Magofuku, Zetao Zhu, Noritada Kaji, Masaki Kanai, Tomoji Kawai, Yoshinobu Baba, Engineering Nanowire-Mediated Cell Lysis for Microbial Cell Identification, ACS Nano, 10.1021/acsnano.8b08959, 2019.01, Researchers have demonstrated great promise for inorganic nanowire use in analyzing cells or intracellular components. Although a stealth effect of nanowires toward cell surfaces allows preservation of the living intact cells when analyzing cells, as a completely opposite approach, the applicability to analyze intracellular components through disrupting cells is also central to understanding cellular information. However, the reported lysis strategy is insufficient for microbial cell lysis due to the cell robustness and wrong approach taken so far (i.e., nanowire penetration into a cell membrane). Here we propose a nanowire-mediated lysis method for microbial cells by introducing the rupture approach initiated by cell membrane stretching; in other words, the nanowires do not penetrate the membrane, but rather they break the membrane between the nanowires. Entangling cells with the bacteria-compatible and flexible nanowires and membrane stretching of the entangled cells, induced by the shear force, play important roles for the nanowire-mediated lysis to Gram-positive and Gram-negative bacteria and yeast cells. Additionally, the nanowire-mediated lysis is readily compatible with the loop-mediated isothermal amplification (LAMP) method because the lysis is triggered by simply introducing the microbial cells. We show that an integration of the nanowire-mediated lysis with LAMP provides a means for a simple, rapid, one-step identification assay (just introducing a premixed solution into a device), resulting in visual chromatic identification of microbial cells. This approach allows researchers to develop a microfluidic analytical platform not only for microbial cell identification including drug- and heat-resistance cells but also for on-site detection without any contamination..
5. Keine Nishiyama, Kanako Sugiura, Noritada Kaji, Manabu Tokeshi, Yoshinobu Baba, Development of a microdevice for facile analysis of theophylline in whole blood by a cloned enzyme donor immunoassay, Lab on a Chip, 10.1039/c8lc01105b, 19, 2, 233-240, 2019.01, We have developed a microdevice for therapeutic drug monitoring. In this device, dispensing of sample and reagent was accomplished by simple manual operation of a syringe. Moreover, for a simple and rapid measurement, we used cloned enzyme donor immunoassay as a detection principle. These features and the reagent that is enclosed in microdevice beforehand make it possible to complete the facile analysis. In this paper, our model analyte was 1,3-dimethylxanthine (theophylline), a kind of bronchodilator. The fluorescence measurement of theophylline in whole blood was achieved with the limit of detection of 0.73 μg mL−1. This microdevice provides rapid analysis (4 min), requires only a small volume of sample (2 μL) and features simple operation; hence, it is readily applicable to point of care testing..
6. Hiroshi Yukawa, Kaoru Suzuki, Keita Aoki, Tomoko Arimoto, Takao Yasui, Noritada Kaji, Tetsuya Ishikawa, Takahiro Ochiya, Yoshinobu Baba, Imaging of angiogenesis of human umbilical vein endothelial cells by uptake of exosomes secreted from hepatocellular carcinoma cells, Scientific Reports, 10.1038/s41598-018-24563-0, 8, 1, 2018.12, Hepatocellular carcinoma (HCC) is a typical hyper-vascular tumor, so the understanding the mechanisms of angiogenesis in HCC is very important for its treatment. However, the influence of the exosomes secreted from HCC cells (HCC-exosomes) on angiogenesis remains poorly understood. We herein examined the effects of the exosomes secreted from HepG2 cells (HepG2-exosomes) on the lumen formation of human umbilical vein endothelial cells (HUVECs) by the imaging of angiogenesis. The degree of lumen formation of HUVECs was dependent on the number of HepG2-exosomes. The HepG2-exosomes expressed NKG2D, an activating receptor for immune cells, and HSP70, a stress-induced heat shock protein associated with angiogenesis through the vascular endothelial growth factor (VEGF) receptor. In addition, the HepG2-exosomes contained several microRNAs (miRNAs) reported to exist in the serum of HCC patients. These results suggest that the HCC-exosomes play an important role in angiogenesis. Further studies on the function of HCC-exosomes may provide a new target for HCC treatment..
7. Hirotoshi Yasaki, Takao Yasui, Takeshi Yanagida, Noritada Kaji, Masaki Kanai, Kazuki Nagashima, Tomoji Kawai, Yoshinobu Baba, A real-time simultaneous measurement on a microfluidic device for individual bacteria discrimination, Sensors and Actuators, B: Chemical, 10.1016/j.snb.2018.01.079, 260, 746-752, 2018.05, Rapid detection of pathogenic bacteria is one of the important social issues for preventing and identifying cause of problems affecting human health. Ionic current sensing through pores has shown the ability to electrically measure bacteria. However, there is an inherent limitation to discriminate chemical characteristics of bacteria for existing ionic current sensing methods Here we propose a real-time simultaneous measurement method, which combines ionic current sensing and fluorescence observation on a microfluidic device. Our method can detect not only the size of individual bacteria passing through a micropore but also observe their stainability based on chemical properties of bacterial cell surface within 300 ms. We succeeded in discriminating each bacterium in a solution mixture including contaminant particles by combining highly accurate ionic current sensing which can detect a size difference of 70 nm, and fluorescence observation which can discriminate internal structures such as those that define bacteria as gram-positive or gram-negative. Our method can be applied to not only on-site bacteria detection but also to screening technology..
8. Mamiko Sano, Noritada Kaji, Qiong Wu, Toyohiro Naito, Takao Yasui, Masateru Taniguchi, Tomoji Kawai, Yoshinobu Baba, Quantitative evaluation of dielectric breakdown of silicon micro- and nanofluidic devices for electrophoretic transport of a single DNA molecule, Micromachines, 10.3390/mi9040180, 9, 4, 2018.04, In the present study, we quantitatively evaluated dielectric breakdown in silicon-based micro- and nanofluidic devices under practical electrophoretic conditions by changing the thickness of the insulating layer. At higher buffer concentration, a silicon nanofluidic device with a 100 nm or 250 nm silicon dioxide layer tolerated dielectric breakdown up to ca. 10 V/cm, thereby allowing successful electrophoretic migration of a single DNA molecule through a nanochannel. The observed DNA migration behavior suggested that parameters, such as thickness of the insulating layer, tolerance of dielectric breakdown, and bonding status of silicon and glass substrate, should be optimized to achieve successful electrophoretic transport of a DNA molecule through a nanopore for nanopore-based DNA sequencing applications..
9. Hirotoshi Yasaki, Taisuke Shimada, Takao Yasui, Takeshi Yanagida, Noritada Kaji, Masaki Kanai, Kazuki Nagashima, Tomoji Kawai, Yoshinobu Baba, Robust Ionic Current Sensor for Bacterial Cell Size Detection, ACS Sensors, 10.1021/acssensors.8b00045, 3, 3, 574-579, 2018.03, Ionic current sensing methods are useful tools for detecting sub- to several-micron scale particles such as bacteria. However, conventional commercially available ionic current sensing devices are not suitable for on-site measurement use because of inherent limitations on their robustness. Here, we proposed a portable robust ionic current sensor (Robust-ICS) using a bridge circuit that offers a high signal-to-noise (S/N) ratio by suppressing background current. Because the Robust-ICS can tolerate increased noise in current sensing, a simple, lightweight electromagnetic shield can be used and measurements under large electromagnetic noise conditions can be made. The weight of the device was lowered below 4 kg and outdoor particle detection measurements were completed successfully. Accuracy of size detection of Staphylococcus aureus (S. aureus) was equivalent to that obtained by SEM imaging..
10. Hirotoshi Yasaki, Takao Yasui, Takeshi Yanagida, Noritada Kaji, Masaki Kanai, Kazuki Nagashima, Tomoji Kawai, Yoshinobu Baba, Effect of channel geometry on ionic current signal of a bridge circuit based microfluidic channel, Chemistry Letters, 10.1246/cl.171139, 47, 3, 350-353, 2018.01, Bridge circuit based ionic current sensing in a microfluidic channel has attracted attention as a highly sensitive analytical method for bio-related molecules and particles. However, channel geometry which greatly influences the detected ionic current has not been investigated. Here, we investigate experimentally and theoretically the effect of differences in the microfluidic channel geometry on shapes and amplitude of signals in ionic current sensing. Our results clarify the geometrical effect of the channel in the bridge circuit based ionic current sensing method..
11. Makusu Tsutsui, Takeshi Yoshida, Kazumichi Yokota, Hirotoshi Yasaki, Takao Yasui, Akihide Arima, Wataru Tonomura, Kazuki Nagashima, Takeshi Yanagida, Noritada Kaji, Masateru Taniguchi, Takashi Washio, Yoshinobu Baba, Tomoji Kawai, Discriminating single-bacterial shape using low-aspect-ratio pores, Scientific Reports, 10.1038/s41598-017-17443-6, 7, 1, 2017.12, Conventional concepts of resistive pulse analysis is to discriminate particles in liquid by the difference in their size through comparing the amount of ionic current blockage. In sharp contrast, we herein report a proof-of-concept demonstration of the shape sensing capability of solid-state pore sensors by leveraging the synergy between nanopore technology and machine learning. We found ionic current spikes of similar patterns for two bacteria reflecting the closely resembled morphology and size in an ultra-low thickness-to-diameter aspect-ratio pore. We examined the feasibility of a machine learning strategy to pattern-analyse the sub-nanoampere corrugations in each ionic current waveform and identify characteristic electrical signatures signifying nanoscopic differences in the microbial shape, thereby demonstrating discrimination of single-bacterial cells with accuracy up to 90%. This data-analytics-driven microporescopy capability opens new applications of resistive pulse analyses for screening viruses and bacteria by their unique morphologies at a single-particle level..
12. Takao Yasui, Takeshi Yanagida, Satoru Ito, Yuki Konakade, Daiki Takeshita, Tsuyoshi Naganawa, Kazuki Nagashima, Taisuke Shimada, Noritada Kaji, Yuta Nakamura, Ivan Adiyasa Thiodorus, Yong He, Sakon Rahong, Masaki Kanai, Hiroshi Yukawa, Takahiro Ochiya, Tomoji Kawai, Yoshinobu Baba, Unveiling massive numbers of cancer-related urinary-microRNA candidates via nanowires, Science advances, 10.1126/sciadv.1701133, 3, 12, 2017.12, Analyzing microRNAs (miRNAs) within urine extracellular vesicles (EVs) is important for realizing miRNA-based, simple, and noninvasive early disease diagnoses and timely medical checkups. However, the inherent difficulty in collecting dilute concentrations of EVs (<0.01 volume %) from urine has hindered the development of these diagnoses and medical checkups. We propose a device composed of nanowires anchored into a microfluidic substrate. This device enables EV collections at high efficiency and in situ extractions of various miRNAs of different sequences (around 1000 types) that significantly exceed the number of species being extracted by the conventional ultracentrifugation method. The mechanical stability of nanowires anchored into substrates during buffer flow and the electrostatic collection of EVs onto the nanowires are the two key mechanisms that ensure the success of the proposed device. In addition, we use our methodology to identify urinary miRNAs that could potentially serve as biomarkers for cancer not only for urologic malignancies (bladder and prostate) but also for nonurologic ones (lung, pancreas, and liver). The present device concept will provide a foundation for work toward the long-term goal of urine-based early diagnoses and medical checkups for cancer..
13. Masatoshi Maeki, Yuka Fujishima, Yusuke Sato, Takao Yasui, Noritada Kaji, Akihiko Ishida, Hirofumi Tani, Yoshinobu Baba, Hideyoshi Harashima, Manabu Tokeshi, Understanding the formation mechanism of lipid nanoparticles in microfluidic devices with chaotic micromixers, PLoS One, 10.1371/journal.pone.0187962, 12, 11, 2017.11, Lipid nanoparticles (LNPs) or liposomes are the most widely used drug carriers for nanomedicines. The size of LNPs is one of the essential factors affecting drug delivery efficiency and therapeutic efficiency. Here, we demonstrated the effect of lipid concentration and mixing performance on the LNP size using microfluidic devices with the aim of understanding the LNP formation mechanism and controlling the LNP size precisely. We fabricated microfluidic devices with different depths, 11 μm and 31 μm, of their chaotic micromixer structures. According to the LNP formation behavior results, by using a low concentration of the lipid solution and the microfluidic device equipped with the 31 μm chaotic mixer structures, we were able to produce the smallest-sized LNPs yet with a narrow particle size distribution. We also evaluated the mixing rate of the microfluidic devices using a laser scanning confocal microscopy and we estimated the critical ethanol concentration for controlling the LNP size. The critical ethanol concentration range was estimated to be 60–80% ethanol. Ten nanometer-sized tuning of LNPs was achieved for the optimum residence time at the critical concentration using the microfluidic devices with chaotic mixer structures. The residence times at the critical concentration necessary to control the LNP size were 10, 15–25, and 50 ms time-scales for 30, 40, and 50 nm-sized LNPs, respectively. Finally, we proposed the LNP formation mechanism based on the determined LNP formation behavior and the critical ethanol concentration. The precise size-controlled LNPs produced by the microfluidic devices are expected to become carriers for next generation nanomedicines and they will lead to new and effective approaches for cancer treatment..
14. Hirotoshi Yasaki, Takao Yasui, Takeshi Yanagida, Noritada Kaji, Masaki Kanai, Kazuki Nagashima, Tomoji Kawai, Yoshinobu Baba, Substantial Expansion of Detectable Size Range in Ionic Current Sensing through Pores by Using a Microfluidic Bridge Circuit, Journal of the American Chemical Society, 10.1021/jacs.7b06440, 139, 40, 14137-14142, 2017.10, Measuring ionic currents passing through nano- or micropores has shown great promise for the electrical discrimination of various biomolecules, cells, bacteria, and viruses. However, conventional measurements have shown there is an inherent limitation to the detectable particle volume (1% of the pore volume), which critically hinders applications to real mixtures of biomolecule samples with a wide size range of suspended particles. Here we propose a rational methodology that can detect samples with the detectable particle volume of 0.01% of the pore volume by measuring a transient current generated from the potential differences in a microfluidic bridge circuit. Our method substantially suppresses the background ionic current from the μA level to the pA level, which essentially lowers the detectable particle volume limit even for relatively large pore structures. Indeed, utilizing a microscale long pore structure (volume of 5.6 × 104 aL; height and width of 2.0 × 2.0 μm; length of 14 μm), we successfully detected various samples including polystyrene nanoparticles (volume: 4 aL), bacteria, cancer cells, and DNA molecules. Our method will expand the applicability of ionic current sensing systems for various mixed biomolecule samples with a wide size range, which have been difficult to measure by previously existing pore technologies..
15. Abdallah M. Zeid, Noritada Kaji, Jenny Jeehan M. Nasr, Fathalla F. Belal, Yoshinobu Baba, Mohamed I. Walash, Stacking-cyclodextrin-microchip electrokinetic chromatographic determination of gabapentinoid drugs in pharmaceutical and biological matrices, Journal of Chromatography A, 10.1016/j.chroma.2017.04.049, 1503, 65-75, 2017.06, A facile, rapid, and highly sensitive microchip-based electrokinetic chromatographic method was developed for the simultaneous analysis of two gabapentinoid drugs, gabapentin (GPN) and pregabalin (PGN). Both drugs were first reacted with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) via nucleophilic substitution reactions to yield highly fluorescent products with λex/em 470/540 nm. Analyses of both fluorescently labeled compounds were achieved within 200 s in a poly(methyl methacrylate) (PMMA) microchip with a 30 mm separation channel. Optimum separation was achieved using a borate buffer (pH 9.0) solution containing methylcellulose and β-cyclodextrin (β-CD) as buffer additives. Methylcellulose acted as a dynamic coating to prevent adsorption of the studied compounds on the inner surfaces of the microchannels, while β-CD acted as a pseudo-stationary phase to improve the separation efficiency between the labeled drugs with high resolution (Rs > 7). The fluorescence intensities of the labeled drugs were measured using a light emitting diode-induced fluorescence detector at 540 nm after excitation at 470 nm. The sensitivity of the method was enhanced 14- and 17-fold for PGN and GPN, respectively by field-amplified stacking relative to traditional pinched injection so that it could quantify 10 ng mL−1 for both analytes, with a detection limit lower than 3 ng mL−1. The developed method was efficiently applied to analyze PGN and GPN in their pharmaceutical dosage forms and in biological fluids. The extraction recoveries of the studied drugs from plasma and urine samples were more than 89% with%RSD values lower than 6.2..
16. Qiong Wu, Noritada Kaji, Takao Yasui, Sakon Rahong, Takeshi Yanagida, Masaki Kanai, Kazuki Nagashima, Manabu Tokeshi, Tomoji Kawai, Yoshinobu Baba, A millisecond micro-RNA separation technique by a hybrid structure of nanopillars and nanoslits, Scientific Reports, 10.1038/srep43877, 7, 2017.03, A millisecond micro-RNA separation of a mixture of total RNA and genomic DNA, extracted from cultured HeLa cells, was successfully achieved using a hybrid structure of nanopillars and nanoslits contained inside a microchannel. The nanopillars, 250-nm in diameter and 100-nm in height, were fabricated with a 750-nm space inside the nanoslits, which were 100-nm in height and 25-μm in width; the nanopillars were then applied as a new sieve matrix. This ultra-fast technique for the separation of miRNA can be an effective pretreatment for semiconductor nanopore DNA sequencing, which has an optimum reading speed of 1 base/ms to obtain effective signal-to-noise ratio and discriminate each base by ion or tunneling current during the passage of nucleic acids..
17. Xiaoyin Sun, Takao Yasui, Takeshi Yanagida, Noritada Kaji, Sakon Rahong, Masaki Kanai, Kazuki Nagashima, Tomoji Kawai, Yoshinobu Baba, Effect of DNA methylation on the velocity of DNA translocation through a nanochannel, Analytical Sciences, 10.2116/analsci.33.727, 33, 6, 727-730, 2017.01, Here, we report the effect of DNA methylation on the velocity of DNA translocation through a nanochannel, as determined by measuring differences in translocation velocities between methylated and non-methylated DNA molecules. We found that the velocity of translocation of methylated DNA was faster than that of non-methylated DNA, which we attributed to variation in the coefficients of diffusion and friction with the nanochannel wall, due to the increased molecular weight and stiffness, respectively, of methylated DNA..
18. Toshihiro Kasama, Noritada Kaji, Manabu Tokeshi, Yoshinobu Baba, Fabrication and evaluation of microfluidic immunoassay devices with antibody-immobilized microbeads retained in porous hydrogel micropillars, Methods in Molecular Biology, 10.1007/978-1-4939-6734-6_4, 49-56, 2017.01, Due to the inherent characteristics including confinement of molecular diffusion and high surface-to-volume ratio, microfluidic device-based immunoassay has great advantages in cost, speed, sensitivity, and so on, compared with conventional techniques such as microtiter plate-based ELISA, latex agglutination method, and lateral flow immunochromatography. In this paper, we explain the detection of C-reactive protein as a model antigen by using our microfluidic immunoassay device, so-called immuno-pillar device. We describe in detail how we fabricated and used the immuno-pillar devices..
19. Xiaoyin Sun, Takao Yasui, Takeshi Yanagida, Noritada Kaji, Sakon Rahong, Masaki Kanai, Kazuki Nagashima, Tomoji Kawai, Yoshinobu Baba, Nanostructures integrated with a nanochannel for slowing down DNA translocation velocity for nanopore sequencing, Analytical Sciences, 10.2116/analsci.33.735, 33, 6, 735-738, 2017.01, Here, we developed a device integrated with a nanochannel and nanostructures to slow DNA translocation velocity. We found that translocation velocity of a single DNA molecule inside a nanochannel was decreased by pre-elongating it using some nanostructures, such as a shallow channel or nanopillars. This decrease of the translocation velocity was associated with the DNA mobility change, which is an intrinsic parameter of DNA molecules and unaffected by an electric field..
20. Takao Yasui, Kensuke Ogawa, Noritada Kaji, Mats Nilsson, Taiga Ajiri, Manabu Tokeshi, Yasuhiro Horiike, Yoshinobu Baba, Label-free detection of real-time DNA amplification using a nanofluidic diffraction grating, Scientific Reports, 10.1038/srep31642, 6, 2016.08, Quantitative DNA amplification using fluorescence labeling has played an important role in the recent, rapid progress of basic medical and molecular biological research. Here we report a label-free detection of real-time DNA amplification using a nanofluidic diffraction grating. Our detection system observed intensity changes during DNA amplification of diffracted light derived from the passage of a laser beam through nanochannels embedded in a microchannel. Numerical simulations revealed that the diffracted light intensity change in the nanofluidic diffraction grating was attributed to the change of refractive index. We showed the first case reported to date for label-free detection of real-time DNA amplification, such as specific DNA sequences from tubercle bacilli (TB) and human papillomavirus (HPV). Since our developed system allows quantification of the initial concentration of amplified DNA molecules ranging from 1 fM to 1 pM, we expect that it will offer a new strategy for developing fundamental techniques of medical applications..
21. Takao Yasui, Jumpei Morikawa, Noritada Kaji, Manabu Tokeshi, Kazuo Tsubota, Yoshinobu Baba, Microfluidic autologous serum eye-drops preparation as a potential dry eye treatment, Micromachines, 10.3390/mi7070113, 7, 7, 2016.07, Dry eye is a problem in tearing quality and/or quantity and it afflicts millions of persons worldwide. An autologous serum eye-drop is a good candidate for dry eye treatment; however, the eye-drop preparation procedures take a long time and are relatively troublesome. Here we use spiral microchannels to demonstrate a strategy for the preparation of autologous serum eye-drops, which provide benefits for all dry eye patients; 100% and 90% removal efficiencies are achieved for 10 μm microbeads and whole human blood cells, respectively. Since our strategy allows researchers to integrate other functional microchannels into one device, such a microfluidic device will be able to offer a new one-step preparation system for autologous serum eye-drops..
22. Yusuke Sato, Yusuke Note, Masatoshi Maeki, Noritada Kaji, Yoshinobu Baba, Manabu Tokeshi, Hideyoshi Harashima, Elucidation of the physicochemical properties and potency of siRNA-loaded small-sized lipid nanoparticles for siRNA delivery, Journal of Controlled Release, 10.1016/j.jconrel.2016.03.019, 229, 48-57, 2016.05, Because nanoparticles with diameters less than 50 nm penetrate stromal-rich tumor tissues more efficiently, the synthesis of small-sized nanoparticles encapsulating short interfering RNA (siRNA) is important in terms of realizing novel siRNA medicine for the treatment of various cancers. Lipid nanoparticles (LNPs) are the leading systems for the delivery of siRNA in vivo. Limit size LNPs were successfully synthesized using a microfluidic mixing technique. However, the physicochemical properties and potential for in vivo siRNA delivery of the limit-size LNPs have not been examined in detail. In the present study, we prepared LNPs with different diameters from 32 to 67 nm using a microfluidic mixing devise and examined the physicochemical properties of the particles and the potential for their use in delivering siRNA in vitro and in vivo to liver. Reducing the size of the LNPs causes poor-packing and an increased surface area, which result in their instability in serum. Moreover, it was revealed that the ability of endosomal escape (cytosolic siRNA release) of the smaller LNPs is subject to inhibition by serum compared to that of larger counterparts. Taken together, an increase in packing and avoiding the adsorption of serum components are key strategies for the development of next-generation highly potent and small-sized LNPs..