Detection of 1,5-anhydroglucitol as a Biomarker for Diabetes Using an Organic Field-Effect Transistor-Based Biosensor

Wide-linearity flexible OFET biosensors for wearable biomarkers detection

Flexible organic field-effect transistor (OFET) sensors, which leverage conjugated π-bonds in organic semiconductor layers to facilitate rapid charge transfer and enhance sensing sensitivity, offer significant advantages for detecting low concentrations of biomarkers in wearable biomedical electronics, such as glucose monitoring for diabetes. However, conventional OFET sensors suffer from a narrow linear range due to limitations in threshold voltage and saturation current. Therefore, a common problem in the field of the OFET-based biomarker sensing is that the narrow linear range of these sensors fails to meet detection requirements. This study addresses this challenge by expanding the linear detection range of OFET glucose sensors to 16.78 μM-1 M through the synergistic integration of four p-type and n-type OFET sensor array. Additionally, to ensure consistency in the fabrication of the sensor array, a fully printed processing technology using a bank structure was developed. Finally, a flexible epidermal continuous blood glucose monitoring system based on the wide-linearity OFET glucose sensor array was constructed to verify its practical feasibility.

Emerging biomarkers in type 2 diabetes mellitus

Diabetes mellitus is a chronic condition caused by high blood glucose resulting from insufficient insulin production or cellular resistance to insulin action or both. It is one of the fastest-growing public health concerns worldwide. Development of long-term nephropathy, retinopathy, neuropathy, and cardiovascular disease are some of the complications commonly associated with poor blood glycemic control. Type 2 diabetes mellitus (T2DM), the most prevalent type of diabetes, accounts for around 95 % of all cases globally. Although middle-aged or older adults are more likely to develop T2DM, its prevalence has grown in children and young people due to increased obesity, sedentary lifestyle and poor nutrition. Furthermore, it is believed that more than 50 % of cases go undiagnosed annually. Routine screening is essential to ensure early detection and reduce risk of life-threatening complications. Herein, we review traditional biomarkers and highlight the ongoing pursuit of novel and efficacious biomarkers driven by the objective of achieving early, precise and prompt diagnoses. It is widely acknowledged that individual biomarkers will inevitably have certain limitations necessitating the need for integrating multiple markers in screening.

Flexible organic field-effect transistors-based biosensors: progress and perspectives

Organic field-effect transistors (OFETs) have been proposed beyond three decades while becoming a research hotspot again in recent years because of the fast development of flexible electronics. Many novel flexible OFETs-based devices have been reported in these years. Among these devices, flexible OFETs-based sensors made great strides because of the extraordinary sensing capability of FET. Most of these flexible OFETs-based sensors were designed for biological applications due to the advantages of flexibility, reduced complexity, and lightweight. This paper reviews the materials, fabrications, and applications of flexible OFETs-based biosensors. Besides, the challenges and opportunities of the flexible OFETs-based biosensors are also discussed.

An Efficient Electrochemical Biosensor to Determine 1,5-Anhydroglucitol with Persimmon-Tannin-Reduced Graphene Oxide-PtPd Nanocomposites

1,5-Anhydroglucitol (1,5-AG) is a sensitive biomarker for real-time detection of diabetes mellitus. In this study, an electrochemical biosensor to specifically detect 1,5-AG levels based on persimmon-tannin-reduced graphene oxide-PtPd nanocomposites (PT-rGO-PtPd NCs), which were modified onto the surface of a screen-printed carbon electrode (SPCE), was designed. The PT-rGO-PtPd NCs were prepared by using PT as the film-forming material and ascorbic acid as the reducing agent. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-vis), and X-ray diffraction (XRD) spectroscopy analysis were used to characterise the newly synthesised materials. PT-rGO-PtPd NCs present a synergistic effect not only to increase the active surface area to bio-capture more targets, but also to exhibit electrocatalytic efficiency to catalyze the decomposition of hydrogen peroxide (H₂O₂). A sensitive layer is formed by pyranose oxidase (PROD) attached to the surface of PT-rGO-PtPd NC/SPCE. In the presence of 1,5-AG, PROD catalyzes the oxidization of 1,5-AG to generate 1,5-anhydrofuctose (1,5-AF) and H₂O₂ which can be decomposed into H₂O under the synergistic catalysis of PT-rGO-PtPd NCs. The redox reaction between PT and its oxidative product (quinones, PTox) can be enhanced simultaneously by PT-rGO-PtPd NCs, and the current signal was recorded by the differential pulse voltammetry (DPV) method. Under optimal conditions, our biosensor shows a wide range (0.1-2.0 mg/mL) for 1,5-AG detection with a detection limit of 30 μg/mL (S/N = 3). Moreover, our electrochemical biosensor exhibits acceptable applicability with recoveries from 99.80 to 106.80%. In summary, our study provides an electrochemical method for the determination of 1,5-AG with simple procedures, lower costs, good reproducibility, and acceptable stability.

Organic small molecule semiconductor materials for OFET-based biosensors

Biosensors is an advanced detection and monitoring device for the development of biotechnology, and is also a rapid and microanalytical device at the molecular level. Demands for high sensitivity, high flexibility, good biocompatibility, easy chemical modification and low cost offer incentive for exploring new materials to develop the next-generation biosensors. With the vigorous development of organic electronics, the performances of organic devices have been effectively improved, leading to organic semiconductor materials with low cost, good flexibility, easy chemical modification and good biocompatibility for biosensors. Biosensors based on organic field-effect transistors (OFETs) have become one of the most advanced biosensor platforms because of their inherent ability to amplify received signals. Furthermore, OFET-based biosensors have been widely used in the detection of DNA, protein, cell, glucose and other biological substances due to its high sensitivity, fast analysis speed, label-free detection, small size and simple operation. This mini review briefly discusses the organic small molecule semiconductor materials, device configurations, basic principles and application fields of OFETs-based biosensors.

Nanozyme-mediated cascade reaction system for electrochemical detection of 1,5-anhydroglucitol

Diabetes is one of metabolic diseases affecting major human health. The early diagnosis and treatment of diabetes have significant benefits. 1,5-anhydroglucitol (1,5-AG) accurately reflects a patient's average blood glucose level for the past 3-7 days and becomes a promising marker for real-time detection of diabetes. In this study, a novel biosensor for determination 1,5-AG is constructed using reduce graphene oxide-carboxymethylated chitosan-hemin@platinum nanocomposites (rGO-CMC-H@Pt NCs) nanozyme and pyranose oxidase (PROD) enzyme as the electrochemical biosensing platform. The rGO-CMC-H@Pt NCs nanozyme has good electro-conductibility, high specific surface area, and admirable peroxide-like catalysis effect to enhance the electrochemical response. 1,5-AG is catalyzed by PROD and produces hydrogen peroxide (H₂O₂), which in turn can be decomposed by rGO-CMC-H@Pt NCs and produce a current signal recorded by differential pulse voltammetry (DPV) technique. Under optimal conditions, the response currents have a linear relationship in the 1,5-AG concentration of 0.1-2.0 mg/mL with R² of 0.9869. The sensitivity is 2.1895 μA/μg·mL^-1 and the limit of detection (LOD) is 38.2 μg/mL (S/N = 3). In addition, the specificity, reproducibility, stability and recovery (94.5-107.6%) of 1,5-AG biosensors all exhibit good performance. Therefore, the designed 1,5-AG biosensor has a good effect and can be used for the diagnosis of diabetes.

Recent Developments in Biomarkers for Diagnosis and Screening of Type 2 Diabetes Mellitus

PURPOSE OF REVIEW

Diabetes mellitus is a complex, chronic illness characterized by elevated blood glucose levels that occurs when there is cellular resistance to insulin action, pancreatic β-cells do not produce sufficient insulin, or both. Diabetes prevalence has greatly increased in recent decades; consequently, it is considered one of the fastest-growing public health emergencies globally. Poor blood glucose control can result in long-term micro- and macrovascular complications such as nephropathy, retinopathy, neuropathy, and cardiovascular disease. Individuals with diabetes require continuous medical care, including pharmacological intervention as well as lifestyle and dietary changes.

RECENT FINDINGS

The most common form of diabetes mellitus, type 2 diabetes (T2DM), represents approximately 90% of all cases worldwide. T2DM occurs more often in middle-aged and elderly adults, and its cause is multifactorial. However, its incidence has increased in children and young adults due to obesity, sedentary lifestyle, and inadequate nutrition. This high incidence is also accompanied by an estimated underdiagnosis prevalence of more than 50% worldwide. Implementing successful and cost-effective strategies for systematic screening of diabetes mellitus is imperative to ensure early detection, lowering patients' risk of developing life-threatening disease complications. Therefore, identifying new biomarkers and assay methods for diabetes mellitus to develop robust, non-invasive, painless, highly-sensitive, and precise screening techniques is essential. This review focuses on the recent development of new clinically validated and novel biomarkers as well as the methods for their determination that represent cost-effective alternatives for screening and early diagnosis of T2DM.

Detection of cellular metabolites by redox enzymatic cascades

Detection of cellular metabolites that are disease biomarkers is important for human healthcare monitoring and assessing prognosis and therapeutic response. Accurate and rapid detection of microbial metabolites and pathway intermediates is also crucial for the process optimization required for development of bioconversion methods using metabolically engineered cells. Various redox enzymes can generate electrons that can be employed in enzyme-based biosensors and in the detection of cellular metabolites. These reactions can directly transform target compounds into various readout signals. By incorporating engineered enzymes into enzymatic cascades, the readout signals can be improved in terms of accuracy and sensitivity. This review critically discusses selected redox enzymatic and chemoenzymatic cascades currently employed for detection of human- and microbe-related cellular metabolites including, amino acids, d-glucose, inorganic ions (pyrophosphate, phosphate, and sulfate), nitro- and halogenated phenols, NAD(P)H, fatty acids, fatty aldehyde, alkane, short chain acids, and cellular metabolites.

1,5-anhydroglucitol biosensor based on light-addressable potentiometric sensor with RGO-CS-Fc/Au NPs nanohybrids

In this paper, a novel silicon-based light-addressable potentiometric sensor (LAPS) has been designed for the detection of 1,5-anhydroglucitol (1,5-AG) in human serum. Reduced graphene oxide-chitosan-ferrocene (RGO-CS-Fc)/AuNPs nanohybrids and pyranose oxidase (PROD) enzyme is used to fabricate biological sensitive membrane unit by layer-by-layer assembly technology. When a bias voltage is provided to the LAPS system, the catalytic oxidation reaction between 1,5-AG and PROD to produce H₂O₂. The by-product H₂O₂ can oxidize Fc(Fe²⁺) ions in RGO-CS-Fc nanohybrids into Fc(Fe³⁺) ions, which cause the potential of the sensitive membrane surface to change and the potential shift of I-V curve will generate a corresponding offset response. Under the optimal conditions, the potential shift of the LAPS is linearly related to the concentration of 1,5-AG at 10 µg·mL^-1 -350 µg·mL^-1 with the correlation coefficient of 0.97414. The sensitivity is 0.44273 mV/µg·mL^-1 and the lowest detection limit is 10 µg·mL^-1. In addition, the biosensor showed good specificity, acceptable stability and satisfactory recovery rates (91.28%-107.66%), which would be a potential testing methods in actual clinical samples.

Organic Bioelectronic Devices for Metabolite Sensing

Electrochemical detection of metabolites is essential for early diagnosis and continuous monitoring of a variety of health conditions. This review focuses on organic electronic material-based metabolite sensors and highlights their potential to tackle critical challenges associated with metabolite detection. We provide an overview of the distinct classes of organic electronic materials and biorecognition units used in metabolite sensors, explain the different detection strategies developed to date, and identify the advantages and drawbacks of each technology. We then benchmark state-of-the-art organic electronic metabolite sensors by categorizing them based on their application area (in vitro, body-interfaced, in vivo, and cell-interfaced). Finally, we share our perspective on using organic bioelectronic materials for metabolite sensing and address the current challenges for the devices and progress to come.

Rapid Detection of SARS-CoV-2 Antigens and Antibodies Using OFET Biosensors Based on a Soft and Stretchable Semiconducting Polymer

In the midst of the COVID-19 pandemic, adaptive solutions are needed to allow us to make fast decisions and take effective sanitation measures, e.g., the fast screening of large groups (employees, passengers, pupils, etc.). Although being reliable, most of the existing SARS-CoV-2 detection methods cannot be integrated into garments to be used on demand. Here, we report an organic field-effect transistor (OFET)-based biosensing device detecting of both SARS-CoV-2 antigens and anti-SARS-CoV-2 antibodies in less than 20 min. The biosensor was produced by functionalizing an intrinsically stretchable and semiconducting triblock copolymer (TBC) film either with the anti-S1 protein antibodies (S1 Abs) or receptor-binding domain (RBD) of the S1 protein, targeting CoV-2-specific RBDs and anti-S1 Abs, respectively. The obtained sensing platform is easy to realize due to the straightforward fabrication of the TBC film and the utilization of the reliable physical adsorption technique for the molecular immobilization. The device demonstrates a high sensitivity of about 19%/dec and a limit of detection (LOD) of 0.36 fg/mL for anti-SARS-Cov-2 antibodies and, at the same time, a sensitivity of 32%/dec and a LOD of 76.61 pg/mL for the virus antigen detection. The TBC used as active layer is soft, has a low modulus of 24 MPa, and can be stretched up to 90% with no crack formation of the film. The TBC is compatible with roll-to-roll printing, potentially enabling the fabrication of low-cost wearable or on-skin diagnostic platforms aiming at point-of-care concepts.

Constructive Optimization of a Multienzymatic Film Based on a Cascade Reaction for Electrochemical Biosensors

The application of a multienzyme cascade reaction in electrochemical biosensors has the advantage of expanding the target substrates in addition to selectivity combining multiple enzymes on an electrode. However, the multienzyme system has the drawback of inefficient substance conversion because of the time-consuming passing of intermediates between the enzymes and/or diffusional loss of the intermediates. In this study, the optimal construction of a multienzymatic film in an ammonia detection sensor was investigated using a cascade reaction of l-glutamate oxidase and l-glutamate dehydrogenase as a model sensor. Three enzymatic films were prepared: (1) a mixed film designed to have a short diffusional distance between closely located enzymes, (2) a normal-sequential layered film arranged for the correct reaction pathway, and (3) a reverse-sequential layered film as a negative control. This was followed by comparison of the conversion efficiency of ammonia to hydrogen peroxide using time-dependent potentiometric measurements of a Prussian blue electrode determining the hydrogen peroxide amount. The results indicate that the conversion efficiency of the normal-sequential layered film was the highest among the three enzymatic films. The quantitative evaluation of the intermediate conversion efficiency of the cascade reaction showed that compared to the mixed film (34%), a higher conversion efficiency of 92% was obtained in the first enzymatic reaction step. These findings will promote the use of multienzymatic cascade reaction systems not only in biosensors and bioreactors but also in various industrial fields.

When Flexible Organic Field-Effect Transistors Meet Biomimetics: A Prospective View of the Internet of Things

The emergence of flexible organic electronics that span the fields of physics and biomimetics creates the possibility for increasingly simple and intelligent products for use in everyday life. Organic field-effect transistors (OFETs), with their inherent flexibility, light weight, and biocompatibility, have shown great promise in the field of biomimicry. By applying such biomimetic OFETs for the internet of things (IoT) makes it possible to imagine novel products and use cases for the future. Recent advances in flexible OFETs and their applications in biomimetic systems are reviewed. Strategies to achieve flexible OFETs are individually discussed and recent progress in biomimetic sensory systems and nervous systems is reviewed in detail. OFETs are revealed to be one of the best systems for mimicking sensory and nervous systems. Additionally, a brief discussion of information storage based on OFETs is presented. Finally, a personal view of the utilization of biomimetic OFETs in the IoT and future challenges in this research area are provided.

Printed Organic Transistor-based Biosensors for Non-invasive Sweat Analysis

This review describes recent advances in biosensors for non-invasive human healthcare applications, especially focusing on sweat analysis, along with approaches for fabricating these biosensors based on printed electronics technology. Human sweat contains various kinds of biomarkers. The relationship between a trace amount of sweat biomarkers partially partitioned from blood and diseases has been investigated by omic analysis. Recent progress in wearable or portable biosensors has enabled periodic or continuous monitoring of some sweat biomarkers while supporting the results of the omic analysis. In this review, we particularly focused on a transistor-based biosensor that is highly sensitive in quantitatively detecting the low level of sweat biomarkers. Furthermore, we showed a new approach of flexible hybrid electronics that has been applied to advanced sweat biosensors to realize fully integrated biosensing systems wirelessly connected to a networked IoT system. These technologies are based on uniquely advanced printing techniques that will facilitate mass fabrication of high-performance biosensors at low cost for future smart healthcare.

Pyranose oxidase: A versatile sugar oxidoreductase for bioelectrochemical applications

Pyranose oxidase (POx) is an FAD-dependent oxidoreductase, and like glucose oxidase (GOx) it is a member of the glucose-methanol-choline (GMC) superfamily of oxidoreductases. POx oxidizes several monosaccharides including D-glucose, D-galactose, and D-xylose, while concurrently oxygen is reduced to hydrogen peroxide. In addition to this oxidase activity, POx shows pronounced activity with alternative electron acceptors that include various quinones or (complexed) metal ions. Even though POx in general shows properties that are more favourable than those of GOx (e.g., a considerably higher catalytic efficiency (k_cat/K_m) for D-glucose, significantly lower Michaelis constants K_m for D-glucose, reactivity with both anomeric forms of D-glucose) it is much less frequently used for both biosensor and biofuel cell applications than GOx. POx has been applied in biosensing of D-glucose, D-galactose, and D-xylose, and in combination with α-glucosidase also maltose. An attractive application is in biosensors constructed for the measurement of 1,5-anhydro-D-glucitol, a recognised biomarker in diabetes. Bioelectrochemical applications of POx had been restricted to enzymes of fungal origin. The recent discovery and characterisation of POx from bacterial sources, which show properties that are very distinct from the fungal enzymes, might open new possibilities for further applications in bioelectrochemistry.

Formaldehyde Detection by a Combination of Formaldehyde Dehydrogenase and Chitosan on a Sensor Based on an Organic Field-Effect Transistor

Formaldehyde is utilized for the preservation of materials due to its strong bactericidal effects. As formaldehyde is also a harmful substance that causes health hazards, the quantitative monitoring of formaldehyde in natural and living environments is desirable. For the rapid and easy detection of formaldehyde, in this study we applied an organic field-effect transistor (OFET)-based sensor that can function as a potentiometric device for electrochemical measurements. A polyion-complex gel of formaldehyde dehydrogenase (FDH) and chitosan (CT) was constructed on a gold electrode. When the FDH/CT gel-coated electrode was connected to an OFET device it could detect formaldehyde in an aqueous solution, in which the amino groups of chitosan would protonate during the enzymatic reaction. The limit of detection was calculated to be 3.1 µM (93 ppb), demonstrating the applicability of the film-type OFET sensor to environmental monitoring.