Koutarou Idegami

Amyloid-β detection with saccharide immobilized gold nanoparticle on carbon electrode

The electrochemical sensing of saccharide-protein interactions using a couple of sialic acid derivatives and Alzheimers amyloid-beta (Abeta) is described. The densely-packed saccharide area for recognition of protein was fabricated onto a carbon electrode by three steps, which were electrochemical deposition of Au nanoparticles on a screen printed strip, self-assembled monolayer (SAM) formation of the acetylenyl group on Au nanoparticles, and the cycloaddition reaction of an azide-terminated sialic acid to the acetylenyl group. The attachment of Abeta peptides to the sialic acid layer was confirmed by electrochemistry and atomic force microscopy imaging. The intrinsic oxidation signal of the captured Abeta(1-40) and (1-42) peptides, containing a single tyrosine (Tyr) residues, was monitored at a peak potential of 0.6 V (vs Ag/AgCl within this sensor) in connection with differential pulse voltammetry. The peak current intensities were concentration dependent. The proposed process provides new routes for analysis of saccharide-protein interactions and electrochemical biosensor development.

Impact of New Quick Gold Nanoparticle-Based Cortisol Assay During Adrenal Vein Sampling for Primary Aldosteronism

CONTEXT Adrenal vein sampling (AVS) is essential for identifying a surgically curable form of primary aldosteronism (PA), but accurate placement of the sampling catheter is technically challenging. Intraprocedural cortisol measurement can confirm the catheters position, thereby increasing the AVS success rate. OBJECTIVE AND METHODS We developed a quick cortisol assay (QCA) that uses immunochromatography and gold nanoparticles and can be performed either semiquantitatively or quantitatively. The assay was evaluated in two studies. In a single-center study, PA patients were assigned to undergo AVS incorporating the semiquantitative QCA (n = 30), the quantitative QCA (n = 30), or without the QCA (n = 30), and the rates of successful AVS were determined. In a prospective multicenter randomized, controlled study, the success rates of AVS performed with (n = 148) or without (n = 145) the semiquantitative QCA were determined. RESULTS Cortisol concentrations were measured during AVS in 6 minutes or less in the radiology suite, without additional technical assistance, and significantly correlated with a conventional reference assay (R(2) = 0.994; P < .001). In the single-center study, the differences in the AVS success rates associated with semiquantitative and quantitative QCAs were not significant (both 93%); however, the success rates were significantly higher than the rate of successful AVS performed without using the QCA (63%; P < .001). The success rate of AVS performed in the multicenter study was 94% for the semiquantitative QCA, which was significantly higher than the rate for the patients without QCA (60%; P < .001). CONCLUSIONS Our novel QCA was rapidly and easily performed at the point of care and improved the rate of successful AVS.

Fabrication and Characterization of Planar Screen-Printed Ag/AgCl Reference Electrode for Disposable Sensor Strip

An accurate disposable planar Ag/AgCl reference electrode with an internal electrolyte was successfully fabricated by the screen-printing process. The internal electrolyte layer was also printed by using an electrolyte paste of sodium alginate containing KCl. The potential stability of the electrode was investigated at different operation times and Cl- concentrations in test solutions. Results show that the electrode has long-term potential stability (approximately 60 min), and that its performance does not depend on the Cl- concentration. This electrode can be used to provide various promising applications in sensing techniques based on disposable strips for sensing purposes.

Development of a High-Sensitive Immunosensor Based on Monitoring Redox Signal of Gold Nanoparticale

A high-sensitive immunosensor was developed monitoring the redox signals of Au nanoparticles in connection with disposable screen-printed carbon strips (SPCSs). All the procedures could be performed on only one strip in a volume of 2 μL solution. Additionally, the direct observation of the Au nanoparticle-labeled antigenantibody complex on the electrode surface was performed by SEM imaging. The changes in the structure of Au nanoparticles during the redox process could be monitored using the high-resolution SEM images. Our immunosensor system, a combination of the screenprinting technology, direct electrical detection of Au nanoparticles with redox enhancement, provides a promising biosensor for various applications in life sciences. The improvement of electrochemical immunosensing schemes using nanomaterials is under intense investigation towards reaching the goals of better sensitivity and selectivity. Au and Ag nanoparticles have been employed intensively in optical methods. The combination of Au nanoparticles and electrochemical detection methods provides a promising platform for the development of highly sensitive and convenient immunosensors. Especially, electrochemical detection methods are widely adapted to biosensor designs because of their small-scale and inexpensive instrumentation and field-portability. In our laboratory, we have recently achieved the development of disposable sensor systems based on the three-electrode type of screen-printed carbon strips (SPCSs) with a strong advantage of fabricating a large number of near identical electrodes at a low cost. With the help of our knowledge on the fabrication of disposable sensors, we designed a disposable immunosensor protocol with Au nanoparticles as illustrated in Scheme 1. The primary antibody was immobilized directly on the working electrode surface, and a series of sandwich-type immuno-reactions was performed (Scheme 1a). Then, a high potential, 1.2 V, was applied to the electrode in 0.1 M HCl for the oxidation of Au nanoparticles, called as the pre-oxidation process (1b), then, the voltammetric measurement was performed (1c).