Chemical Sensing Platforms Based on Organic Thin-Film Transistors Functionalized with Artificial Receptors

Quantitative Spermidine Detection in Cosmetics using an Organic Transistor-Based Chemical Sensor

Spermidine is an essential biomarker related to antiaging. Although the detection of spermidine levels is in high demand in life science fields, easy-to-use analytical tools without sample purification have not yet been fully established. Herein, we propose an organic field-effect transistor-based chemical sensor for quantifying the spermidine concentration in commercial cosmetics. An extended-gate structure was employed for organic field-effect transistor (OFET)-based chemical sensing in aqueous media. A coordination-bond-based sensing system was introduced into the OFET device to visualize the spermidine detection information through changes in the transistor characteristics. The extended-gate-type OFET has shown quantitative responses to spermidine, which indicates sufficient detectability (i. e., the limit of detection for spermidine: 2.3 μM) considering actual concentrations in cosmetics. The applicability of the OFET-based chemical sensor for cosmetic analysis was validated by instrumental analysis using high-performance liquid chromatography. The estimated recovery rates for spermidine in cosmetic ingredient products (108-111 %) suggest the feasibility of cosmetic analysis based on the OFET-based chemical sensor.

An extended-gate-type organic transistor for monitoring the Menschutkin reaction of tetrazole at a solid-liquid interface

We herein propose an approach to visualize the Menschutkin reaction at an interface between a self-assembled monolayer with nucleophilic properties and water containing alkyl halides. An organic field-effect transistor functionalized with a nucleophilic monolayer has detected in situ alkylation depending on differences in the leaving group ability and the bulkiness of electrophilic alkyls.

An organic transistor for detecting the oxidation of an organic sulfur compound at a solid-liquid interface and its chemical sensing applications

The development of chemical sensors has advanced due to an increase in demand; however, the potential of chemical sensors as devices to monitor organic reactions has not been revealed yet. Thus, we aim to propose a chemical sensor platform for facile monitoring of chemical reactions, especially at a solid-liquid interface. In this study, an extended-gate-type organic field-effect transistor (OFET) has been employed as a platform to detect chemical reactions at an interface between the extended-gate electrode and an aqueous solution. The OFET device functionalized with 4,4'-thiobisbenzenthiol has shown time- and concentration-dependent shifts in transistor characteristics upon adding H2O2. In a selectivity test using seven oxidant agents, the transistor responses depended on the oxidation of the organic sulfur compound (i.e., 4,4'-thiobisbenzenthiol) stemming from the ability of the oxidant agents. Therefore, the observed changes in the transistor characteristics have suggested the generation of sulfur-oxidized products at the interface. In this regard, the observed responses were caused by disulfide formation accompanied by changes in the charges under neutral pH conditions. Meanwhile, weak transistor responses derived from the generation of oxygen adducts have also been observed, which were caused by changes in the dipole moments. Indeed, the yields of the oxygen adducts have been revealed by X-ray photoelectron spectroscopy. The monitoring of gradual changes originating from the decrease in the disulfide formation and the increase in the oxygen adducts implied a novel aspect of the OFET device as a platform to simultaneously detect reversible and irreversible reactions at interfaces without using large-sized analytical instruments. Sulfur oxidation by H2O2 on the OFET device has been further applied to the indirect monitoring of an enzymatic reaction in solution. The OFET-based chemical sensor has shown continuous changes with an increase in a substance (i.e., lactate) in the presence of an enzyme (i.e., lactate oxidase), which indicates that the OFET response depends on the H2O2 generated through the enzymatic reaction in the solution. In this study, we have clarified the versatility of organic devices as platforms to monitor different chemical reactions using a single detection method.

Healthcare Monitoring Sensors Based on Organic Transistors: Surface/Interface Strategy and Performance

Organic transistors possess inherent advantages such as flexibility, biocompatibility, customizable chemical structures, solution-processability, and amplifying capabilities, making them highly promising for portable healthcare sensor applications. Through convenient and diverse modifications at the material and device surfaces or interfaces, organic transistors allow for a wide range of sensor applications spanning from chemical and biological to physical sensing. In this comprehensive review, the surface and interface engineering aspect associated with four types of typical healthcare sensors is focused. The device operation principles and sensing mechanisms are systematically analyzed and highlighted, and particularly surface/interface functionalization strategies that contribute to the enhancement of sensing performance are focused. An outlook and perspective on the critical issues and challenges in the field of healthcare sensing using organic transistors are provided as well.

Carbon dots-functionalized extended gate organic field effect transistor-based biosensors for low abundance proteins

Organic field effect transistors have emerged as promising platforms for biosensing applications. However, the challenge lies in optimizing functionalization strategies for the sensing interface, enabling the simultaneous detection of low abundance proteins while maintaining device performance. Here, we designed a carbon dots-functionalized extended gate organic field effect transistor. Leveraging the advantages of facile synthesis, tunable modification, small particle size, and cost-effectiveness of carbon dots, we implemented their integration onto the electrode surface. Through harnessing the covalent interactions of functional groups on the surface of carbon dots, we achieved effective immobilization of low abundance proteins without compromising device performance. Consequently, this biosensor exhibits a remarkably low limit of detection of 2.7 pg mL-1 and demonstrates high selectivity for the carcinoembryonic antigen. These findings highlight the superior capabilities of carbon dots in enhancing biosensor performance and emphasize their potential for early cancer detection.

Integration of nanomaterial sensing layers on printable organic field effect transistors for highly sensitive and stable biochemical signal conversion

Organic field effect transistor (OFET) devices are one of the most popular candidates for the development of biochemical sensors due to their merits of being flexible and highly customizable for low-cost large-area manufacturing. This review describes the key points in constructing an extended-gate type OFET (EGOFET) biochemical sensor with high sensitivity and stability. The structure and working mechanism of OFET biochemical sensors are described firstly, emphasizing the importance of critical material and device engineering to higher biochemical sensing capabilities. Next, printable materials used to construct sensing electrodes (SEs) with high sensitivity and stability are presented with a focus on novel nanomaterials. Then, methods of obtaining printable OFET devices with steep subthreshold swing (SS) for high transconductance efficiency are introduced. Finally, approaches for the integration of OFETs and SEs to form portable biochemical sensor chips are introduced, followed by several demonstrations of sensory systems. This review will provide guidelines for optimizing the design and manufacturing of OFET biochemical sensors and accelerating the movement of OFET biochemical sensors from the laboratory to the marketplace.

Non-enzymatic detection of glucose levels in human blood plasma by a graphene oxide-modified organic transistor sensor

We herein report an organic transistor functionalized with a phenylboronic acid derivative and graphene oxide for the quantification of plasma glucose levels, which has been achieved by the minimization of interferent effects derived from physical protein adsorption on the detection electrode.

In Vivo Electrochemical Biosensors: Recent Advances in Molecular Design, Electrode Materials, and Electrochemical Devices

Electrochemical biosensors provide powerful tools for dissecting the dynamically changing neurochemical signals in the living brain, which contribute to the insight into the physiological and pathological processes of the brain, due to their high spatial and temporal resolutions. Recent advances in the integration of in vivo electrochemical sensors with cross-disciplinary advances have reinvigorated the development of in vivo sensors with even better performance. In this Review, we summarize the recent advances in molecular design, electrode materials, and electrochemical devices for in vivo electrochemical sensors from molecular to macroscopic dimensions, highlighting the methods to obtain high performance for fulfilling the requirements for determination in the complex brain through flexible and smart design of molecules, materials, and devices. Also, we look forward to the development of next-generation in vivo electrochemical biosensors.

Liquid crystalline self-assembly of azulene-thiophene hybrids and their applications as OFET materials

Orientational control within thin films is crucial for the preparation of organic field effect transistors (OFETs). The highly ordered liquid crystalline smectic E phase (SmE) is known as a powerful template for solution processed thin films. Here, we describe the synthesis and characterization of three novel azulene-thiophene hybrid materials. Liquid crystalline characterization showed the presence of wide SmE phases. Thin films were prepared by spin-coating at mesophase temperature. Due to the self-aligning properties of the SmE phase uniformly flat films with good molecular alignment were manufactured. Top contact bottom gate OFETs showed mobilities up to (3.3 ± 0.5) × 10^-3 cm² V^-1 s^-1.

An organic transistor for the selective detection of tropane alkaloids utilizing a molecularly imprinted polymer

This study proposes a chemical sensing approach for the selective detection of tropane alkaloid drugs based on an extended-gate-type organic field-effect transistor (OFET) functionalized with a molecularly imprinted polymer (MIP). From the viewpoint of pharmaceutical chemistry, the development of versatile chemical sensors to determine the enantiomeric purity of over-the-counter (OTC) tropane drugs is important because of their side effects and different pharmacological activities depending on their chirality. To this end, we newly designed an OFET sensor with an MIP (MIP-OFET) as the recognition element for tropane drugs based on a high complementarity among a template (i.e., (S)-hyoscyamine) and functional monomers such as N-isopropylacrylamide and 2,2-dimethyl-4-pentenoic acid. Indeed, the MIP optimized by density functional theory (DFT) has succeeded in the sensitive and selective detection of (S)-hyoscyamine (as low as 1 μM) by the combination of the OFET with highly selective recognition sites in the MIP. The MIP-OFET was further applied to determine the enantiomeric excess (ee) of commercially available (S)-hyoscyamine, and the linearity changes in the threshold voltages of the OFET corresponded to the % ee values of (S)-hyoscyamine. Overall, the validation with tropane alkaloids revealed the potential of the MIP combined with OFET as a chemical sensor chip for OTC drugs in real-world scenarios.

Environmental Response Sensors Produced Using Bilayer-Type Organic Semiconductors

In this study, we developed environmental gas sensors based on bilayer-type organic semiconductors. The number of stacked molecular bilayers was controlled through a solution-based approach. In particular, single molecular bilayers (SMBs) were produced through a geometrical frustration method that can effectively suppress the multiple stacking of bilayers. The layer number-controlled films were utilized to form thin-film transistors (TFTs) to detect the moisture in the air. We revealed that the sensitivity was enhanced in the SMB-based TFTs compared with the TFTs with thicker active layers. These findings are expected to facilitate a new route for producing flexible and lightweight chemical sensors.

A microfluidic organic transistor for reversible and real-time monitoring of H2O2 at ppb/ppt levels in ultrapure water

A microfluidic organic transistor functionalized with phenylboronic acid firstly succeeded in reversible and real-time monitoring of H₂O₂ at ppb/ppt levels in ultrapure water, which would be used not only as portable chemical sensors but also as monitoring tools to clarify unknown reaction mechanisms of phenylboronic acid with H₂O₂.

Molecularly imprinted polymers via reversible addition-fragmentation chain-transfer synthesis in sensing and environmental applications

Molecularly imprinted polymers (MIP) have shown their potential as artificial and selective receptors for environmental monitoring. These materials can be tailor-made to achieve a specific binding event with a template through a chosen mechanism. They are capable of emulating the recognition capacity of biological receptors with superior stability and versatility of integration in sensing platforms. Commonly, these polymers are produced by traditional free radical bulk polymerization (FRP) which may not be the most suitable for enhancing the intended properties due to the poor imprinting performance. To improve the imprinting technique and the polymer capabilities, controlled/living radical polymerization (CRP) has been used to overcome the main drawbacks of FRP. Combining CRP techniques such as RAFT (reversible addition-fragmentation chain transfer) with MIP has achieved higher selectivity, sensitivity, and sorption capacity of these polymers when implemented as the transductor element in sensors. The present work focuses on RAFT-MIP design and synthesis strategies to enhance the binding affinities and their implementation in environmental contaminant sensing applications.

The Need to Pair Molecular Monitoring Devices with Molecular Imaging to Personalize Health

By enabling the non-invasive monitoring and quantification of biomolecular processes, molecular imaging has dramatically improved our understanding of disease. In recent years, non-invasive access to the molecular drivers of health versus disease has emboldened the goal of precision health, which draws on concepts borrowed from process monitoring in engineering, wherein hundreds of sensors can be employed to develop a model which can be used to preventatively detect and diagnose problems. In translating this monitoring regime from inanimate machines to human beings, precision health posits that continual and on-the-spot monitoring are the next frontiers in molecular medicine. Early biomarker detection and clinical intervention improves individual outcomes and reduces the societal cost of treating chronic and late-stage diseases. However, in current clinical settings, methods of disease diagnoses and monitoring are typically intermittent, based on imprecise risk factors, or self-administered, making optimization of individual patient outcomes an ongoing challenge. Low-cost molecular monitoring devices capable of on-the-spot biomarker analysis at high frequencies, and even continuously, could alter this paradigm of therapy and disease prevention. When these devices are coupled with molecular imaging, they could work together to enable a complete picture of pathogenesis. To meet this need, an active area of research is the development of sensors capable of point-of-care diagnostic monitoring with an emphasis on clinical utility. However, a myriad of challenges must be met, foremost, an integration of the highly specialized molecular tools developed to understand and monitor the molecular causes of disease with clinically accessible techniques. Functioning on the principle of probe-analyte interactions yielding a transducible signal, probes enabling sensing and imaging significantly overlap in design considerations and targeting moieties, however differing in signal interpretation and readout. Integrating molecular sensors with molecular imaging can provide improved data on the personal biomarkers governing disease progression, furthering our understanding of pathogenesis, and providing a positive feedback loop toward identifying additional biomarkers and therapeutics. Coupling molecular imaging with molecular monitoring devices into the clinical paradigm is a key step toward achieving precision health.

Multi-Oxyanion Detection by an Organic Field-Effect Transistor with Pattern Recognition Techniques and Its Application to Quantitative Phosphate Sensing in Human Blood Serum

We herein report an organic field-effect transistor (OFET) based chemical sensor for multi-oxyanion detection with pattern recognition techniques. The oxyanions ubiquitously play versatile roles in biological systems, and accessing the chemical information they provide would potentially facilitate fundamental research in diagnosis and pharmacology. In this regard, phosphates in human blood serum would be a promising indicator for early case detection of significant diseases. Thus, the development of an easy-to-use chemical sensor for qualitative and quantitative detection of oxyanions is required in real-world scenarios. To this end, an extended-gate-type OFET has been functionalized with a metal complex consisting of 2,2'-dipicolylamine and a copper(II) ion (CuII-dpa), allowing a compact chemical sensor for oxyanion detection. The OFET combined with a uniform CuII-dpa-based self-assembled monolayer (SAM) on the extended-gate gold electrode shows a cross-reactive response, which suggests a discriminatory power for pattern recognition. Indeed, the qualitative detection of 13 oxyanions (i.e., hydrogen monophosphate, pyrophosphate, adenosine monophosphate, adenosine diphosphate, adenosine triphosphate, terephthalate, phthalate, isophthalate, malonate, oxalate, lactate, benzoate, and acetate) has been demonstrated by only using a single OFET-based sensor with linear discriminant analysis, which has shown 100% correct classification. The OFET has been further applied to the quantification of hydrogen monophosphate in human blood serum using a support vector machine (SVM). The multiple predictions of hydrogen monophosphate at 49 and 89 μM have been successfully realized with low errors, which indicates that the OFET-based sensor with pattern recognition techniques would be a practical sensing platform for medical assays. We believe that a combination of the OFET functionalized with the SAM-based recognition scaffold and powerful pattern recognition methods can achieve multi-analyte detection from just a single sensor.

Titanium oxide-based optoelectronic synapses with visual memory synergistically adjusted by internal emotions and ambient illumination

Brain-inspired neuromorphic computing has become one of the critical technologies to overcome the bottleneck of von Neumann architecture. It is a vital step to construct a brain-like neuromorphic computing system at the hardware level by utilizing artificial synaptic devices. Compared with electronic synaptic devices, optoelectronic synaptic devices have the advantages of low power consumption, low crosstalk, and high bandwidth. Artificial optoelectronic synapses, analogous to retinal structure, can directly respond to and process light signal information to mimic the neuromorphic visual system. As high-level nerve impulses, both generated and regulated, emotions affect the strength and persistence of memory. Ambient illumination can provide visual perception to distinguish the size, color, and other characteristics of objects as well as affect the nonvisual functions of individuals, such as emotional states, thereby affecting learning and memory function. Herein, an artificial optoelectronic synapse composed of ITO/TiO_2−x/p-Si was proposed. A variety of biologically dependent synaptic plasticity relating to learning and memory, including short-term synaptic plasticity, long-term synaptic plasticity, and learning-forgetting-relearning multifunctional advanced synaptic activity, was successfully simulated. A 3 × 3 artificial optoelectronic synapse array based on 9 devices was constructed to mimic the functions of visual learning and memory affected by internal emotion and ambient illumination. The proposed artificial optoelectronic synapse will exhibit great potential in visual and image information perception and memory.

A variety of biologically dependent synaptic plasticity activities were simulated on artificial optoelectronic synapse devices. An array was constructed to mimic the functions of visual learning and memory affected by internal emotion and ambient illumination.

Highly Stable Electrochemical Probe with Bidentate Thiols for Ratiometric Monitoring of Endogenous Polysulfide in Living Mouse Brains

The lack of reliable approaches for real-time measurement and quantification of polysulfides (H₂S_n) in vivo greatly limits the exploration of their potential roles in brain functions. Herein, an electrochemical probe, 4-(5-(1,2-dithiolan-3-yl)pentanamido)-1,2-phenylene bis(2-fluoro-5-nitrobenzoate) (FP2), was rationally designed and created for determination of H₂S_n. The bis-electrophilic groups of FP2 could specifically recognize two -SH groups in H₂S_n and trigger the generation of an electroactive pyrocatechol moiety, resulting in a well-defined faradic current signal at ∼0.24 V (vs Ag/AgCl). Meanwhile, bidentate thiols were designed as anchoring sites to greatly improve the assembled stability of FP2 at the Au surface, which efficiently defended the interference of glutathione (GSH) with a current decrease of less than 5.2% even after long-term measurements in 5 mM GSH for 3 h. In addition, a stable inner reference molecule with dithiols, α-lipoic acid ferrocenylamide (FcBT), was synthesized to construct a ratiometric electrochemical strategy for in vivo determination of H₂S_n through one-step coassembling with FP2 via double S-Au bonds. The present ratiometric strategy demonstrated high selectivity for real-time tracking of H₂S_n in a linear range of 0.25-20 μM. Eventually, the developed microelectrode with high selectivity, accuracy, and stability was employed for in vivo assaying of H₂S_n in mouse brains with ischemia.

Real-Time Detection of Glyphosate by a Water-Gated Organic Field-Effect Transistor with a Microfluidic Chamber

This paper reports the development of a real-time monitoring system utilizing the combination of a water-gated organic field-effect transistor (WG-OFET) and a microfluidic chamber for the detection of the herbicide glyphosate (GlyP). For the realization of the real-time sensing with the WG-OFET, the surface of a polymer semiconductor was utilized as a sensing unit. The aqueous solution including the target analyte, which is employed as a gate dielectric of the WG-OFET, flows into a designed microfluidic chamber on the semiconductor layer and the gate electrode. As the sensing mechanism, the WG-OFET-based sensor utilizes the competitive complexation among carboxylate-functionalized polythiophene, a copper(II) (Cu²⁺) ion, and GlyP. The reversible accumulation and desorption of the positively charged Cu²⁺ ion on the semiconductor surface induced a change in the electrical double-layer capacitance (EDLC). The optimization of the microfluidic chamber enables a uniform water flow and contributes to real-time quantitative sensing of GlyP at a micromolar level. Thus, this study would lead to practical real-time sensing in water for various fields including environmental assessment.

Extended gate-type organic transistor functionalized by molecularly imprinted polymer for taurine detection

Molecularly imprinted polymers (MIPs) are a fascinating technology for the sensitive and selective detection of target molecules. However, in most situations, the need for complicated and expensive analytical devices for reading the responses of MIPs greatly limits their applications. For exploring low-cost and easy-to-use applications of MIPs, herein we have developed a MIP-modified extended-gate type organic field-effect transistor (MIP-OFET). Taurine was selected as a demonstrative analyte due to its biological roles and utility as a nutrient. We explored the rational design of the novel MIP with the aid of density functional theory and wave function calculations and characterized the electrochemically synthesized MIP using differential pulse voltammetry and electrochemical impedance spectroscopy. The mechanism of taurine detection by the MIP-OFET can be explained by the changes in the surface potential of the MIP-functionalized extended-gate electrode accompanied with the capture of taurine. The detection limit of taurine in complete aqueous media was estimated to be 0.33 μM, which was lower or comparable to those calculated by high-performance liquid chromatography. Furthermore, taurine in a commercial drink without any extraction was also successfully detected using the fabricated MIP-OFET. This study would broaden the scope of the applications of MIP-OFETS as chemical sensors for on-site detection of various daily nutrients.

A Robust Au-C≡C Functionalized Surface: Toward Real-Time Mapping and Accurate Quantification of Fe2+ in the Brains of Live AD Mouse Models

Described here is that Au-C≡C bonds showed the highest stability under biological conditions, with abundant thiols, and the best electrochemical performance compared to Au-S and Au-Se bonds. The new finding was also confirmed by theorical calculations. Based on this finding, a specific molecule for recognition of Fe²⁺ was designed and synthesized, and used to create a selective and accurate electrochemical sensor for the quantification of Fe²⁺ . The present ratiometric strategy demonstrates high spatial resolution for real-time tracking of Fe²⁺ in a dynamic range of 0.2-120 μM. Finally, a microelectrode array with good biocompatibility was applied in imaging and biosensing of Fe²⁺ in the different regions of live mouse brains. Using this tool, it was discovered that the uptake of extracellular Fe²⁺ into the cortex and striatum was largely mediated by cyclic adenosine monophosphate (cAMP) through the CREB-related pathway in the brain of a mouse with Alzheimer's disease.

Protein Assays on Organic Electronics: Rational Device and Material Designs for Organic Transistor-Based Sensors

Artificial receptor-based protein assays have various attractive features such as a long-term stability, a low-cost production process, and the ease of tuning the target specificity. However, such protein sensors are still immature compared with conventional immunoassays. To enhance the application potential of synthetic sensing materials, organic field-effect transistors (OFETs) are some of the suitable platforms for protein assays because of their solution processability, durability, and compact integration. Importantly, OFETs enable the electrical readout of the protein recognition phenomena of artificial receptors on sensing electrodes. Thus, we believe that OFETs functionalized with artificial protein receptors will be a powerful tool for the on-site analyses of target proteins. In this Minireview, we summarize the recent progress of the OFET-based protein assays including the rational design strategies for devices and sensing materials.

The Power of Assemblies at Interfaces: Nanosensor Platforms Based on Synthetic Receptor Membranes

Synthetic sensing materials (artificial receptors) are some of the most attractive components of chemical/biosensors because of their long-term stability and low cost of production. However, the strategy for the practical design of these materials toward specific molecular recognition in water is not established yet. For the construction of artificial material-based chemical/biosensors, the bottom-up assembly of these materials is one of the effective methods. This is because the driving forces of molecular recognition on the receptors could be enhanced by the integration of such kinds of materials at the 'interfaces', such as the boundary portion between the liquid and solid phases. Additionally, the molecular assembly of such self-assembled monolayers (SAMs) can easily be installed in transducer devices. Thus, we believe that nanosensor platforms that consist of synthetic receptor membranes on the transducer surfaces can be applied to powerful tools for high-throughput analyses of the required targets. In this review, we briefly summarize a comprehensive overview that includes the preparation techniques for molecular assemblies, the characterization methods of the interfaces, and a few examples of receptor assembly-based chemical/biosensing platforms on each transduction mechanism.

Systematic Investigation of Molecular Recognition Ability in FET-Based Chemical Sensors Functionalized with a Mixed Self-Assembled Monolayer System

Exploring new strategies for simple and on-demand methods of manipulating the sensing ability of sensor devices functionalized with artificial receptors embedded in a molecular assembly is important to realizing high-throughput on-site sensing systems based on integrated and miniaturized devices such as field-effect transistors (FETs). Although FET-based chemical sensors can be used for rapid, quantitative, and simultaneous determination of various desired analytes, detectable targets in conventional FET sensors are currently restricted owing to the complicated processes used to prepare sensing materials. In this study, we investigated the relationship between the sensing features of FETs and the nanostructures of mixed self-assembled monolayers (mSAMs) for the detection of biomolecules. The FET devices were systematically functionalized using mixtures of benzenethiol derivatives (4-mercaptobenzoic acid and benzenethiol), which changed the nanostructure of the SAMs formed on gold sensing electrodes. The obtained cross-reactivity in the FETs modified with the mSAMs was derived from the multidimensional variations of the SAM characteristics. Our successful demonstration of continuous control of the molecular recognition ability in the FETs by applying the mSAM system could lead to the development of next-generation versatile analyzers, including chemical sensor arrays for the determination of multiple analytes anytime, anywhere.

Recent Electrochemical/Electrical Microfabricated Sensor Devices for Ionic and Polyionic Analytes

The recent technological advances combined with the development of new concepts and strategies have revolutionized the field of sensor devices, allowing access to increasingly sophisticated device structures associated with high sensitivities and selectivities. Among them, electrochemical and electrical sensors have gained the most interest because they offer unique intrinsic characteristics and meet the requirements to be integrated in more sophisticated devices including microfluidics or lab-on-chips, opening access to multiplex and all-in-one detection devices. In the present article, we outline and provide a short and concise overview on the most recent achievements in the field of electrical detection of ionic species as they display versatile roles in many important biological events and are ubiquitous in environment.