Yuji Miyahara

Bio: Yuji Miyahara is an academic researcher from Tokyo Medical and Dental University. The author has contributed to research in topics: Field-effect transistor & Biosensor. The author has an hindex of 47, co-authored 332 publications receiving 7045 citations. Previous affiliations of Yuji Miyahara include National Institute for Materials Science & Kyushu University.

Design of an open-tubular column liquid chromatograph using silicon chip technology

Abstract: A novel concept of high pressure liquid chromatography is presented, involving a silicon chip with an open-tubular column and a conductometric detector, a chip holder and a pressure pulse driven injector using a conventional liquid chromatography pump and valves. The design and optimization of the chromatograph and the chip are discussed. A 5 × 5 mm chip containing an open-tubular column of 6 μm × 2 μm × 15 cm was fabricated, which has theoretical separation efficiencies of 8000 and 25 000 plates in 1 and 5 min, respectively. The total column volume is 1.5 nanoliter and the detection cell volume 1.2 picoliter.

Phenylboronic Acid-Installed Polymeric Micelles for Targeting Sialylated Epitopes in Solid Tumors

Abstract: Ligand-mediated targeting of nanocarriers to tumors is an attractive strategy for increasing the efficiency of chemotherapies. Sialylated glycans represent a propitious target as they are broadly overexpressed in tumor cells. Because phenylboronic acid (PBA) can selectively recognize sialic acid (SA), herein, we developed PBA-installed micellar nanocarriers incorporating the parent complex of the anticancer drug oxaliplatin, for targeting sialylated epitopes overexpressed on cancer cells. Following PBA-installation, the micelles showed high affinity for SA, as confirmed by fluorescence spectroscopy even at intratumoral pH conditions, i.e., pH 6.5, improving their cellular recognition and uptake and enhancing their in vitro cytotoxicity against B16F10 murine melanoma cells. In vivo, PBA-installed micelles effectively reduced the growth rate of both orthotopic and lung metastasis models of melanoma, suggesting the potential of PBA-installed nanocarriers for enhanced tumor targeting

A Synthetic Approach Toward a Self‐Regulated Insulin Delivery System

Abstract: Stimuli-responsive “smart gels” that undergo physicochemical property changes in response to external stimuli can provide both a functional and structural basis for selfregulated materials and systems. Of particular interest are those materials sensitive to chemical stimuli, that is, the fluctuation in the concentration of specific biomolecules, that can mimic biofeedback systems, thus providing many attractive platforms for biomedical applications. Glucose has been a molecule of interest for decades owing to its relevance to the treatment of diabetes. Diabetes is not an infectious disease, but its rapidly increasing worldwide prevalence has been recognized as a pandemic, and thus diabetes poses a serious global health threat much like epidemics of truly infectious diseases, such as HIV/AIDS. Despite the necessity for the continuous and accurate glycemic control in the management of insulin-dependent diabetes mellitus (IDDM), the current palliative treatment relies almost solely on the patients self injection of insulin; this self injection not only impinges on the quality of life of the patient but also fails to precisely control the dose of insulin, where an overdose must be strictly avoided as it causes serious hypoglycemia. For the preparation of self-regulated insulin delivery systems, the following two approaches have historically prevailed. One is based on enzymatic reactions between glucose oxidase (GOD) and glucose, a similar rationale to those exploited in commercial glucose sensors. The other type utilizes carbohydrate-binding lectin proteins, such as concanavalin A (Con A), as a complementary binder to glucose. These protein-based materials eventually denature and lose activity, and thus are not practical for long-term use and storage. Another problem is the strong cytotoxicity of Con A; this cytotoxicity has, thus far, prevented any clinical applications of these materials. Herein we describe a totally synthetic alternative to these materials. Phenylboronic acid (PBA), a synthetic molecule capable of reversibly binding with 1,2or 1,3-cis-diols including glucose, is utilized as the molecular basis. Our previous studies have shown that the glucose-dependent shift in the equilibrium of PBA between the uncharged and anionically charged forms, when coupled with a properly amphiphilic three-dimensional backbone (or gel), could induce a reversible change in the volume of the gel. The resultant abrupt and rapid change in the hydration, under certain conditions, could cause a localized dehydration of the gel surface, that is, a so-called skin layer, thus offering a method to instantly control the permeation of gel-loaded insulin. This goal is a great challenge and relies on achieving sufficient glucose sensitivity under physiological pH and temperature, that is, pH 7.4 and 37 8C, while also fine tuning the system so it shows a gated response to the change in glucose concentration critically at the level of normoglycemia, i.e., ca. 1 gl . To achieve this goal, we have systemically explored the structure–property correlation by focusing on (meth)acrylamide-based hydrogels. The major efforts have been directed to controlling the apparent pKa of PBA; the pKa depends not only on chemical structure of PBA, but also on the state of hydration. To make the situation more complicated, in a hydrogel environment the degree of hydration is a function of (as well as temperature, ionic strength, pH, and sugar concentration) the hydrophilicity, rigidity, and density of the main chain components and the amount of PBA. Herein we describe a gel that meets all the above criteria; the chemical structure of this gel turned out to be a remarkably simple copolymer system. A smart gel has been shown to act as an artificial pancreas under conditions closely related to human glucose homeostasis. As illustrated in Figure 1a, PBA derivatives in water exist in equilibrium between uncharged (i) and anionically charged (ii) forms. Upon addition of glucose, only the charged PBA (ii) can form a stable complex with glucose (iii), and the formation of this complex results in an apparent decrease in the amount of anionically charged PBA (ii). On consumption of the phenylboronate (ii), the equilibrium between (i) and (ii) shifts toward the latter (ii). Since the complexed PBA (iii) is also anionically charged, further addition of glucose leads to a shift in the equilibrium (i + ii + iii) toward the phenylboronate anions (ii + iii), and a decrease in the amount of [*] Dr. A. Matsumoto, J. Nishida, Dr. H. Matsumoto, Dr. Y. Miyahara Institute of Biomaterials and Bioengineering Tokyo Medical and Dental University Kanda-surugadai 2-3-10, Chiyoda-ku, Tokyo 101-0062 (Japan) E-mail: miyahara.bsr@tmd.co.jp Dr. T. Ishii Department of Bioengineering, The University of Tokyo Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 (Japan)

A phenylboronate-functionalized polyion complex micelle for ATP-triggered release of siRNA

Abstract: Therapeutics based on small interfering RNA (siRNA) offer an attractive clinical option because of its ability to silence genes in a highly sequence-specific manner. [1] A key challenge lies in developing a delivery system that helps protect the siRNAs from endogenous RNase degradation while allowing for controlled pharmacokinetics. One promising approach is a formulation of polyion complex (PIC) micelles that spontaneously form in an aqueous environment simply through electrostatic interactions between the anionic siRNA and cationic polymers. With versatile designs of the counterpart cationic polymers, representative poly(ethylene glycol) based block co-polymers, many creative PIC-based strategies have emerged, some of which have shown encouraging in vitro gene silencing abilities. However, in general, these PIC-based carriers suffer from instability under physiological conditions, primarily because of the relatively short chain length of the siRNA, that is 20–25 nucleotides, which results in poor thermodynamic stability. Therefore, stabilization of the PIC-based carriers so that programmed destabilization upon arrival at the site of intracellular targets (to release siRNA) has been of interest. Current efforts have focused on either one or combinations of the following three representative approaches: covalent conjugation of siRNAs to a homing polymer, introduction of hydrophobic moieties to reinforce the core-aggregation, and crosslinking the core aggregate by disulfide bridging. 12] As such, the combination of these approaches often results in a highly complex structure and method of preparation. Herein, we describe a sophisticated solution that can remarkably simplify the synthesis of PICs. It uses a phenylboronate functionality, which incorporates all of the aforementioned methods of stabilization (Scheme 1) while maintaining a wide window of control for environmental sensitivity. Phenylboronic acid (PBA) is a synthetic molecule capable of forming reversible covalent esters with 1,2or 1,3-cis-diols including on a ribose ring, a structure which is present at the 3’ end of RNAs and several kinds of ribonucleotides. Because of this property, PBA has historically been used as a ligand for RNA in affinity chromatography. Therefore, this binding property offers a facile route for chemical conjugation of siRNAs to the pendant PBA groups. Once electrostatically condensed into the PIC, the chances of equilibrium binding are increased, in which intermolecular cross-links could also form because of the bis-bidentate ribose arrangement at the 3’ end of the double-stranded siRNA, thereby further stabilizing the complex. Furthermore, PBA is unique in that it undergoes a dramatic inversion in its level of hydrophobicity depending on the degree of acid disassociation; it is strongly hydrophobic when uncharged but it becomes hydrophilic when negatively charged at pH values above its pKa. As shown in Figure 1, the binding between PBA and siRNAs is essentially a reversible equilibrium process dependent on the concentrations of each species. These features can be used to fine-tune or switch the stability of the complex, which is relevant to creating a system that is sensitive to the interand intracellular environments. Herein, we demonstrate that the PBA-assisted PIC micelles can be tailored to exhibit a dramatic disruption accompanied by the release of siRNAs in response to a change in the ribose concentration (which parallels events in the intracellular environment). A platform cationic polymer poly(ethylene glycol)-blockpoly(l-lysine) (PEG-b-PLys) was first prepared, the lysine residues of which were quantitatively modified with 3-fluoro4-carboxyphenylboronic acid (FPBA) to different extents. The weight-average molecular weight (Mw) of PEG and the mean degree of polymerization of PLys were determined to be 12000 Da and 42, respectively (Supporting Information, Table S1). The synthesized polymers are referred to as PEGb-P(Lys/FPBAX)42, where X denotes number of FPBA units introduced per polymer chain. According to the scattered light intensity of the polymer solutions, polymers were soluble (at 5 mgmL ) in HEPES buffered solution (HBS, pH 7.3) up to 55% FPBA modification, that is (PEG-b-P(Lys/FPBA23)42, however, those with 66 % (that is (PEG-b-P(Lys/FPBA28)42) or higher degrees of FPBA modification were partially insoluble because of the strong hydrophobicity of FPBA (data not shown). The HBS-soluble series of polymers, that is PEG-b-P(Lys/FPBA0,10,19,23)42, were allowed to complex with siRNA at various N/P ratios, which is defined as the molar [*] M. Naito, Dr. K. Kataoka Department of Materials Engineering, The University of Tokyo Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 (Japan) E-mail: kataoka@bmw.t.u-tokyo.ac.jp Homepage: http://www.bmw.t.u-tokyo.ac.jp/

Noninvasive sialic acid detection at cell membrane by using phenylboronic acid modified self-assembled monolayer gold electrode.

Abstract: Alternations of sialic acid (SA) content on cell surface glycan chains have been implicated in numerous normal and pathological processes including developments, differentiations, and tumor metastasis. Overexpressions of SA have been implicated in the malignant and metastatic phenotypes for many different types of cancers, while decreased SA expression has also been identified in erythrocytes of diabetic mellitus. Techniques to conveniently monitor cell surface SA would therefore have great relevance to cytology. Preexisting methodologies to quantify SA, however, involve multiple enzymatic, dye-labeling, and lethal procedures, which are costly and time-consuming. Here we developed a potentiometric SA detection using a phenylboronic acid (PBA) compound integrated into the form of a self-assembled monolayer (SAM) onto a field effect transistor (FET) extended gold gate electrode. Due to selective binding between undisassociated PBA and SA at pH 7.4 among other glycan chain constituent monosaccharides, we found that carboxyl anions of SA were exclusively detectable as the change in threshold voltage (V(T)) of the PBA-modified FET. The technique was applied to analyses of altered SA expressions on rabbit erythrocyte as a model for diabetes. Comparative SA expression analyses for each healthy and diseased model revealed that the disease could be feasibly diagnosed simply by placing the known-count cell suspensions onto the device without any labeling and enzymatic procedures. Such a technique may also provide a quantitative adjunct to histological evaluation of tumor malignancy and metastatic potential during intra- and postoperative diagnoses. Also advantageously, a technique herein described is all within a CMOS (Complementary Metal Oxide Semiconductor) compatible format thus promising for highly efficient and low cost manufacturing with readiness of downsizing and integration by virtue of advanced semiconductor processing technologies.

Miniaturized total chemical analysis systems: A novel concept for chemical sensing

Abstract: Following the trend towards smaller channel inner diameter for better separation performance and shorter channel length for shorter transport time, a modular construction of a miniaturized 'total chemical analysis system' is proposed. The theoretical performances of such systems based on flow injection analysis, chromatography and electrophoresis, are compared with those of existing chemical sensors and analysis systems.

Designing materials for biology and medicine

Abstract: Biomaterials have played an enormous role in the success of medical devices and drug delivery systems. We discuss here new challenges and directions in biomaterials research. These include synthetic replacements for biological tissues, designing materials for specific medical applications, and materials for new applications such as diagnostics and array technologies.

Graphene Based Electrochemical Sensors and Biosensors: A Review

Abstract: Graphene, emerging as a true 2-dimensional material, has received increasing attention due to its unique physicochemical properties (high surface area, excellent conductivity, high mechanical strength, and ease of functionalization and mass production). This article selectively reviews recent advances in graphene-based electrochemical sensors and biosensors. In particular, graphene for direct electrochemistry of enzyme, its electrocatalytic activity toward small biomolecules (hydrogen peroxide, NADH, dopamine, etc.), and graphenebased enzyme biosensors have been summarized in more detail; Graphene-based DNA sensing and environmental analysis have been discussed. Future perspectives in this rapidly developing field are also discussed.

An integrated semiconductor device enabling non-optical genome sequencing

Abstract: The seminal importance of DNA sequencing to the life sciences, biotechnology and medicine has driven the search for more scalable and lower-cost solutions. Here we describe a DNA sequencing technology in which scalable, low-cost semiconductor manufacturing techniques are used to make an integrated circuit able to directly perform non-optical DNA sequencing of genomes. Sequence data are obtained by directly sensing the ions produced by template-directed DNA polymerase synthesis using all-natural nucleotides on this massively parallel semiconductor-sensing device or ion chip. The ion chip contains ion-sensitive, field-effect transistor-based sensors in perfect register with 1.2 million wells, which provide confinement and allow parallel, simultaneous detection of independent sequencing reactions. Use of the most widely used technology for constructing integrated circuits, the complementary metal-oxide semiconductor (CMOS) process, allows for low-cost, large-scale production and scaling of the device to higher densities and larger array sizes. We show the performance of the system by sequencing three bacterial genomes, its robustness and scalability by producing ion chips with up to 10 times as many sensors and sequencing a human genome.

Analyte Monitoring Device And Methods Of Use

Abstract: An analyte monitor includes a sensor, a sensor control unit, and a display unit. The sensor has, for example, a substrate, a recessed channel formed in the substrate, and conductive material disposed in the recessed channel to form a working electrode. The sensor control unit typically has a housing adapted for placement on skin and is adapted to receive a portion of an electrochemical sensor. The sensor control unit also includes two or more conductive contacts disposed on the housing and configured for coupling to two or more contact pads on the sensor. A transmitter is disposed in the housing and coupled to the plurality of conductive contacts for transmitting data obtained using the sensor. The display unit has a receiver for receiving data transmitted by the transmitter of the sensor control unit and a display coupled to the receiver for displaying an indication of a level of an analyte. The analyte monitor may also be part of a drug delivery system to alter the level of the analyte based on the data obtained using the sensor.