Anti-drug antibody detection with label-free electrolyte-gated organic field-effect transistors

Bioelectronic Large-Area Transistors for High-Performance Sensing

Bioelectronics, originating from Galvani's eighteenth-century experiments, blends biology, medicine, and electronics to create devices that can be closely connected to biological systems. This review focuses on bioelectronic large-area field-effect transistor (FET) sensing devices, emphasizing their sensitivity, specificity, and reliability. The role of analytical chemistry in optimizing performance-level control is pivotal, and the review discusses key performance metrics, including limit of identification (LOI), reliability and selectivity. The assessment of the LOI level is addressed using examples of FET-based bioelectronic sensors capable of detecting concentrations at least in the picomolar range. Examples of sensors capable of detecting concentrations in the tens of zeptomolar range are also provided, demonstrating that a single molecule in 0.1 mL can be reliably detected. Working at the LOI also minimizes random errors, which can be as low as 1%. The review also explores the use of molecularly imprinted polymers for highly selective FET bioelectronic detections, noting their sustainability and robustness in comparison to natural antibodies.

Dual-compartment-gate organic transistors for monitoring biogenic amines from food

According to the Food and Agriculture Organization of the United Nations (FAO) more than 14% of the world's food production is lost every year before reaching retail, and another 17% is lost during the retail stage. The use of the expiration date as the main estimator of the life-end of food products creates unjustified food waste. Sensors capable of quantifying the effective food freshness and quality could substantially reduce food waste and enable more effective management of the food chain. We propose an electrolyte-gated organic transistor (EGOT) that responds to the release of biogenic amines, like diamines and tyramine, generated by the degradation of protein-rich food. The EGOT sensor features a polymeric poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) gate electrode fabricated in the shape of a miniaturized beaker containing an aqueous solution in the inner side (to be exposed to food) and capacitively coupled through a hydrogel to the transistor channel on the outside (not in contact with food). The hydrogen bonds formed by the water-dissolved amines with PEDOT:PSS modulate the EGOT channel across a wide range of amine concentrations. We demonstrate that our sensor can detect different amines by the combinatorial analysis of the response from different channel materials, PEDOT:PSS and the other DPP-DTT, with a limit of detection as low as 100 pM.

Flexible Organic Transistors for Biosensing: Devices and Applications

Flexible and stretchable biosensors can offer seamless and conformable biological-electronic interfaces for continuously acquiring high-fidelity signals, permitting numerous emerging applications. Organic thin film transistors (OTFTs) are ideal transducers for flexible and stretchable biosensing due to their soft nature, inherent amplification function, biocompatibility, ease of functionalization, low cost, and device diversity. In consideration of the rapid advances in flexible-OTFT-based biosensors and their broad applications, herein, a timely and comprehensive review is provided. It starts with a detailed introduction to the features of various OTFTs including organic field-effect transistors and organic electrochemical transistors, and the functionalization strategies for biosensing, with a highlight on the seminal work and up-to-date achievements. Then, the applications of flexible-OTFT-based biosensors in wearable, implantable, and portable electronics, as well as neuromorphic biointerfaces are detailed. Subsequently, special attention is paid to emerging stretchable organic transistors including planar and fibrous devices. The routes to impart stretchability, including structural engineering and material engineering, are discussed, and the implementations of stretchable organic transistors in e-skin and smart textiles are included. Finally, the remaining challenges and the future opportunities in this field are summarized.

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.

Reduced Graphene Oxide Electrolyte-Gated Transistor Immunosensor with Highly Selective Multiparametric Detection of Anti-Drug Antibodies

The advent of immunotherapies with biological drugs has revolutionized the treatment of cancers and auto-immune diseases. However, in some patients, the production of anti-drug antibodies (ADAs) hampers the drug efficacy. The concentration of ADAs is typically in the range of 1-10 pm; hence their immunodetection is challenging. ADAs toward Infliximab (IFX), a drug used to treat rheumatoid arthritis and other auto-immune diseases, are focussed. An ambipolar electrolyte-gated transistor (EGT) immunosensor is reported based on a reduced graphene oxide (rGO) channel and IFX bound to the gate electrode as the specific probe. The rGO-EGTs are easy to fabricate and exhibit low voltage operations (≤ 0.3 V), a robust response within 15 min, and ultra-high sensitivity (10 am limit of detection). A multiparametric analysis of the whole rGO-EGT transfer curves based on the type-I generalized extreme value distribution is proposed. It is demonstrated that it allows to selectively quantify ADAs also in the co-presence of its antagonist tumor necrosis factor alpha (TNF-α), the natural circulating target of IFX.

Recent Advances in Field Effect Transistor Biosensors: Designing Strategies and Applications for Sensitive Assay

In comparison with traditional clinical diagnosis methods, field-effect transistor (FET)-based biosensors have the advantages of fast response, easy miniaturization and integration for high-throughput screening, which demonstrates their great technical potential in the biomarker detection platform. This mini review mainly summarizes recent advances in FET biosensors. Firstly, the review gives an overview of the design strategies of biosensors for sensitive assay, including the structures of devices, functionalization methods and semiconductor materials used. Having established this background, the review then focuses on the following aspects: immunoassay based on a single biosensor for disease diagnosis; the efficient integration of FET biosensors into a large-area array, where multiplexing provides valuable insights for high-throughput testing options; and the integration of FET biosensors into microfluidics, which contributes to the rapid development of lab-on-chip (LOC) sensing platforms and the integration of biosensors with other types of sensors for multifunctional applications. Finally, we summarize the long-term prospects for the commercialization of FET sensing systems.

Large-Area Interfaces for Single-Molecule Label-free Bioelectronic Detection

Bioelectronic transducing surfaces that are nanometric in size have been the main route to detect single molecules. Though enabling the study of rarer events, such methodologies are not suited to assay at concentrations below the nanomolar level. Bioelectronic field-effect-transistors with a wide (μm²-mm²) transducing interface are also assumed to be not suited, because the molecule to be detected is orders of magnitude smaller than the transducing surface. Indeed, it is like seeing changes on the surface of a one-kilometer-wide pond when a droplet of water falls on it. However, it is a fact that a number of large-area transistors have been shown to detect at a limit of detection lower than femtomolar; they are also fast and hence innately suitable for point-of-care applications. This review critically discusses key elements, such as sensing materials, FET-structures, and target molecules that can be selectively assayed. The amplification effects enabling extremely sensitive large-area bioelectronic sensing are also addressed.

Electrolyte-gated transistors for enhanced performance bioelectronics

Electrolyte-gated transistors (EGTs), capable of transducing biological and biochemical inputs into amplified electronic signals and stably operating in aqueous environments, have emerged as fundamental building blocks in bioelectronics. In this Primer, the different EGT architectures are described with the fundamental mechanisms underpinning their functional operation, providing insight into key experiments including necessary data analysis and validation. Several organic and inorganic materials used in the EGT structures and the different fabrication approaches for an optimal experimental design are presented and compared. The functional bio-layers and/or biosystems integrated into or interfaced to EGTs, including self-organization and self-assembly strategies, are reviewed. Relevant and promising applications are discussed, including two-dimensional and three-dimensional cell monitoring, ultra-sensitive biosensors, electrophysiology, synaptic and neuromorphic bio-interfaces, prosthetics and robotics. Advantages, limitations and possible optimizations are also surveyed. Finally, current issues and future directions for further developments and applications are discussed.

Sensing Inflammation Biomarkers with Electrolyte-Gated Organic Electronic Transistors

An overview of cytokine biosensing is provided, with a focus on the opportunities provided by organic electronic platforms for monitoring these inflammation biomarkers which manifest at ultralow concentration levels in physiopathological conditions. Specifically, two of the field's state-of-the-art technologies-organic electrochemical transistors (OECTs) and electrolyte gated organic field effect transistors (EGOFETs)-and their use in sensing cytokines and other proteins associated with inflammation are a particular focus. The overview will include an introduction to current clinical and "gold standard" quantification techniques and their limitations in terms of cost, time, and required infrastructure. A critical review of recent progress with OECT- and EGOFET-based protein biosensors is presented, alongside a discussion onthe future of these technologies in the years and decades ahead. This is especially timely as the world grapples with limited healthcare diagnostics during the Coronavirus disease (COVID-19)pandemic where one of the worst-case scenarios for patients is the "cytokine storm." Clearly, low-cost point-of-care technologies provided by OECTs and EGOFETs can ease the global burden on healthcare systems and support professionals by providing unprecedented wealth of data that can help to monitor disease progression in real time.

Label free detection of miRNA-21 with electrolyte gated organic field effect transistors (EGOFETs)

We report a dual gate/common channel organic transistor architecture designed for quantifying the concentration of one of the strands of miRNA-21 in solution. The device allows one to measure the differential response between two gate electrodes, viz. one sensing and one reference, both immersed in the electrolyte above the transistor channel. Hybridization with oligonucleotide in the picomolar regime induces a sizable reduction of the current flowing through the transistor channel. The device signal is reported at various gate voltages, showing maximum sensitivity in the sublinear regime, with a limit of detection as low as 35 pM. We describe the dose curves with an analytical function derived from a thermodynamic model of the reaction equilibria relevant in our experiment and device configuration, and we show that the apparent Hill dependence on analyte concentration, whose exponent lies between 0.5 and 1, emerges from the interplay of the different equilibria. The binding free energy characteristic of the hybridization on the device surface is found to be approximately 20% lower with respect to the reaction in solution, hinting to partially inhibiting effect of the surface and presence of competing reactions. Impedance spectroscopy and surface plasmon resonance (SPR) performed on the same oligonucleotide pair were correlated to the electronic current transduced by the EGOFET, and confirmed the selectivity of the biorecognition probe covalently bound on the gold surface.