Estimation of Extracellular Matrix Production Using a Cultured-Chondrocyte-Based Gate Ion-Sensitive Field-Effect Transistor

Signal transduction interfaces for field-effect transistor-based biosensors

Biosensors based on field-effect transistors (FETs) are suitable for use in miniaturized and cost-effective healthcare devices. Various semiconductive materials can be applied as FET channels for biosensing, including one- and two-dimensional materials. The signal transduction interface between the biosample and the channel of FETs plays a key role in translating electrochemical reactions into output signals, thereby capturing target ions or biomolecules. In this Review, distinctive signal transduction interfaces for FET biosensors are introduced, categorized as chemically synthesized, physically structured, and biologically induced interfaces. The Review highlights that these signal transduction interfaces are key in controlling biosensing parameters, such as specificity, selectivity, binding constant, limit of detection, signal-to-noise ratio, and biocompatibility.

Micro- and nano-devices for electrochemical sensing

Electrode miniaturization has profoundly revolutionized the field of electrochemical sensing, opening up unprecedented opportunities for probing biological events with a high spatial and temporal resolution, integrating electrochemical systems with microfluidics, and designing arrays for multiplexed sensing. Several technological issues posed by the desire for downsizing have been addressed so far, leading to micrometric and nanometric sensing systems with different degrees of maturity. However, there is still an endless margin for researchers to improve current strategies and cope with demanding sensing fields, such as lab-on-a-chip devices and multi-array sensors, brain chemistry, and cell monitoring. In this review, we present current trends in the design of micro-/nano-electrochemical sensors and cutting-edge applications reported in the last 10 years. Micro- and nanosensors are divided into four categories depending on the transduction mechanism, e.g., amperometric, impedimetric, potentiometric, and transistor-based, to best guide the reader through the different detection strategies and highlight major advancements as well as still unaddressed demands in electrochemical sensing.

Graphical Abstract

Technical Perspectives on Applications of Biologically Coupled Gate Field-Effect Transistors

Biosensing technologies are required for point-of-care testing (POCT). We determine some physical parameters such as molecular charge and mass, redox potential, and reflective index for measuring biological phenomena. Among such technologies, biologically coupled gate field-effect transistor (Bio-FET) sensors are a promising candidate as a type of potentiometric biosensor for the POCT because they enable the direct detection of ionic and biomolecular charges in a miniaturized device. However, we need to reconsider some technical issues of Bio-FET sensors to expand their possible use for biosensing in the future. In this perspective, the technical issues of Bio-FET sensors are pointed out, focusing on the shielding effect, pH signals, and unique parameters of FETs for biosensing. Moreover, other attractive features of Bio-FET sensors are described in this perspective, such as the integration and the semiconductive materials used for the Bio-FET sensors.

Detection of cell membrane proteins using ion-sensitive field effect transistors combined with chemical signal amplification

The capture and detection of cells expressing a breast-cancer related membrane protein, namely a BT474 cell line expressing HER2, is demonstrated using ion-sensitive field effect transistors (ISFETs). BT474 cells were exposed to anti-HER2 antibodies and urease-conjugated secondary antibodies to induce chemical signal amplification by adding urea.

Electrochemical Cell-based Biosensors for Biomedical Applications

Abstract:

Electrochemical cell-based biosensors have been showing increasing interest within the last 15 years, with a large number of reports generally dealing with the sensors’ sensitivity, selectivity, stability, signal-to-noise ratio, spatiotemporal resolution, etc. However, only a few of them are now available as commercial products on the market. In this review, technological advances, current challenges and opportunities of electrochemical cell-based biosensors are presented. The article encompasses emerging studies, mainly focusing on the last five years (from 2016 to mid 2021), towards cell-based biological field-effect devices, cell-based impedimetric sensors and cell-based microelectrode arrays. In addition, special attention lies on recent progress in recording at the single-cellular level, including intracellular monitoring with high spatiotemporal resolution as well as integration into microfluidics for lab-on-a-chip applications. Moreover, a comprehensive discussion on challenges and future perspectives will address the future potential of electrochemical cell-based biosensors.

Solution-Gated Ultrathin Channel Indium Tin Oxide-Based Field-Effect Transistor Fabricated by a One-Step Procedure that Enables High-Performance Ion Sensing and Biosensing

In this paper, we propose a one-step procedure for fabricating a solution-gated ultrathin channel indium tin oxide (ITO)-based field-effect transistor (FET) biosensor, thus providing an ″all-by-ITO″ technology. A thin-film sheet was placed on both ends of a metal shadow mask, which were contacted with a glass substrate. That is, the bottom of the metal shadow mask corresponding to the channel was slightly raised from the substrate, resulting in the creeping of some particles into the gap during sputtering. Owing to this modified metal shadow mask, a thin ITO channel (<30-40 nm) and thick ITO source/drain electrodes (ca. 100 nm) were simultaneously fabricated during the one-step sputtering. The thickness of ITO films was critical for them to be semiconductive, depending on the maximum depletion width (∼30-40 nm for the ITO channel), similarly to 2D materials. The ultrathin ITO channel worked as an ion-sensitive membrane as well owing to the intrinsic oxidated surface directly contacting with an electrolyte solution. The solution-gated 20-nm-thick channel ITO-based FET, with a steep subthreshold slope (SS) of 55 mV/dec (pH 7.41) attributable to the electric double-layer capacitance at the electrolyte solution/channel interface and the absence of interfacial traps among electrodes formed in one step, demonstrated an ideal pH responsivity (∼56 mV/pH), resulting in the real-time monitoring of cellular respiration and the long-term stability of electrical properties for 1 month. Moreover, the chemical modification of the ITO channel surface is expected to contribute to biomolecular recognition with ultrahigh sensitivity owing to the remarkably steep SS, which provided the exponential pH sensitivity in the subthreshold regime. Our new device produced in this one-step manner has a great future potential in bioelectronics.

Cell Adhesion Characteristics on Tantalum Pentoxide Gate Insulator for Cultured-Cell-Gate Field-Effect Transistor

Understanding the interaction between living cells and a tantalum pentoxide (Ta₂O₅) gate electrode is important for controlling cell adhesion and functions when developing a cultured-cell-gate field-effect transistor biosensor. In this study, we evaluate the cell adhesion characteristics of the Ta₂O₅ membrane without or with a polydopamine (pDA) coating for chondrocytes, which is expected as a treatment for improving biocompatibility. As a result, the native and pDA-modified Ta₂O₅ membranes are shown to have the appropriate surface tension (35-40 dyn/cm) for the adhesion of chondrocytes owing to the contribution of surface tension to not only the nonspecific adsorption of serum proteins as the scaffold of chondrocytes but also the maintenance of the conformation of serum proteins. In particular, the serum proteins adhere more efficiently to the native Ta₂O₅ membrane than to the pDA-modified ones owing to the relatively smaller surface tension of the native Ta₂O₅ membrane; as a result, the proliferation and production of extracellular matrix (ECM) proteins such as collagen and proteoglycans by chondrocytes are clearly enhanced on the native Ta₂O₅ membrane. Thus, the native Ta₂O₅ membrane shows superior performance for the chondrocyte culture on it compared with the pDA-modified ones.