Toshiya Sakata

We have been developing a genetic field-effect transistor (FET) based on the potentiometric detection of hybridization and intercalation on the Si 3 N 4 gate insulator. In this study, we demonstrated the detection of charge density change as a result of hybridization and intercalation using genetic FETs. Since the electrical output signal is obtained with the genetic FET without any labeling reagent, as compared with the conventional fluorescence-based DNA chips, the genetic FET platform is suit

In charge: Label-free DNA sequencing can be performed by using a field-effect transistor to detect the intrinsic molecular charges (see picture). Oligonucleotide probes are immobilized on the Si3N4 gate surface, and complementary target DNA is hybridized with them. The change in charge density on the Si3N4/SiO2 gate caused by each single-base extension can be measured as a shift in the threshold voltage. VG=gate voltage.

Potentiometric measurement of allele-specific oligonucleotide hybridization based on the principle of detection of charge-density change at the surface of a gate insulator by using of a genetic field-effect transistor has been demonstrated. Since DNA molecules are negatively charged in aqueous solution, a hybridization event at the gate surface leads to a charge-density change in the channel of the FET and can be directly transduced into an electrical signal without any labeling of target DNA mo

It is important to eliminate the tear samples contaminated with blood. Tear glucose monitoring might be a reliable and non-invasive substitute method for monitoring the blood glucose concentrations for diabetes patients, irrespective of glycated hemoglobin levels and timing of sample collection.

In this paper, recent works on biologically coupled gate field-effect transistor (bio-FET) sensors are introduced and compared to provide a perspective. Most biological phenomena are closely related to behaviors of ions and biomolecules. This is why biosensing devices for detecting ionic and biomolecular charges contribute to the direct analysis of biological phenomena in a label-free and enzyme-free manner. Potentiometric biosensors such as bio-FET sensors, which allow the direct detection of t

In this paper, we propose a highly sensitive and biocompatible glucose sensor using a semiconductor-based field effect transistor (FET) with a functionalized hydrogel. The principle of the FET device contributes to the easy detection of ionic charges with high sensitivity, and the hydrogel coated on the electrode enables the specific detection of glucose with biocompatibility. The copolymerized hydrogel on the Au gate electrode of the FET device is optimized by controlling the mixture ratio of b

We proposed an interface molecule for immobilization of DNA probes on solid substrates of DNA chips. We have designed and synthesized tripodal thiol derivatives for stable immobilization of oligonucleotide probes on a gold surface. On the basis of the tetrahedral structure of tripod, the tripodal thiol derivatives were bonded upright to the gold substrate, which would control the orientation of oligonucleotide probes. When the gold substrate with oligonucleotide probes tethered using the thiol d

In this study, we proposed a new detection method, open sandwich-based immuno-field effect transistor (OS-FET) for label-free and noncompetitive detection of low molecular weight antigen. The principle of OS-FET is based on the detection of intrinsic molecular charges caused by the small antigen-dependent interchain interaction of separated V(L) and V(H) chains from a single antibody variable region using the field effect. Introducing V(H) chain and small antigen bisphenol A into the OS-FET with

We propose potentiometric detection of biomolecules using an extended-gate field-effect transistor (EGFET). Using a gold film electrode as the extended gate, the stability of the interface potential was characterized for a shift and a drift, and found to depend on the surface roughness of the gold electrode. The surface of the gold film was coated with self-assembled monolayers (SAMs) of various types of alkanethiol molecules with functional sites such as amino groups, carboxyl groups, hydroxyl

We demonstrated the live monitoring of cellular respiration using an ion-sensitive field-effect transistor (ISFET), focusing on different types of living cells, namely cancer and normal cells. In particular, we realized the label-free, real-time, and noninvasive monitoring of microenvironmental pH behavior based on extracellular acidosis around cancer cells in the long term and in situ. The change in interfacial pH (ΔpH_int), which was analyzed based on the change in interfacial potent

In this paper, we proposed to enhance a signal-to-noise (S/N) ratio for detecting a primary stress marker, serotonin, using a potentiometric biosensor modified by a well-designed nanofilter film. An extended-Au-gate field-effect transistor (EG-Au-gate FET) biosensor exhibits highly sensitive electrochemical detection toward various small biomolecules, including serotonin. Therefore, to enhance the S/N ratio for the serotonin detection, we designed an appropriate nanofilter film on the Au electro