Fast, specific, and ultrasensitive antibiotic residue detection by monolayer WS2-based field-effect transistor sensor

Application and development of signal amplification strategy in detection of antibiotic residues in food

Food is essential for the proper functioning of the human body, and small molecule contaminants, such as antibiotics, have become a growing concern due to their harmful effects on both biological systems and the environment. These contaminants can enter the food supply through the use of antibiotics in animals, potentially causing significant health and ecological damage. As a result, detecting these pollutants, especially at trace levels, has become increasingly important. Aptamer sensors have gained popularity for this purpose because of their high stability, specificity, ease of modification, and low cost. To improve the sensitivity of these sensors, various signal enhancement strategies are used. These strategies aim to better detect small molecule contaminants, with many relying on nanomaterials and nucleic acid amplification techniques to amplify signals. Nanomaterials, which come in different forms such as zero-dimensional, one-dimensional, two-dimensional, and three-dimensional, play a crucial role in improving the performance of these sensors. This article provides an overview of these signal enhancement approaches, discussing the challenges and potential future directions for the development of aptamers in food contamination detection.

Dual nuclease-amplified sensitive biosensor for enrofloxacin detection using a DNase I-assisted CRISPR/Cas12a (CRISPR-DNase I) system

Recent years have witnessed the flourishing of CRISPR/Cas-based biosensors in various fields. However, most of them were developed for nucleic acid detection because non-nucleic acid targets are unable to unleash the cleavage activity of the CRISPR/Cas system directly. To circumvent this problem, activator DNA and deoxyribonuclease I (DNase I) were introduced in this research to render the CRISPR/Cas12a system as a new powerful tool for the detection of enrofloxacin (ENR), a common veterinary drug. In this biosensor, target ENR competed with DNase I- and bovine serum albumin-ENR composite-modified gold nanoparticles (DNase I-AuNPs-BSA-ENR) for the binding sites on the surface of antibody-modified magnetic nanoparticles (immuno-MNPs). Then, the captured DNase I-AuNPs-BSA-ENR degraded the activator DNA in the solution, which inhibited the activation of the CRISPR/Cas12a system. Finally, the fluorescence released by the activated CRISPR/Cas12a system was measured for the quantitative detection of ENR. The ingenious use of activator DNA and DNase I helped transduce the target recognition event into the cleavage activity of the CRISPR/Cas12a system. Moreover, the dual enzymatic amplification from DNase I and the CRISPR/Cas12a system guaranteed the sensitivity of this method with a low detection limit of 0.04 ng/mL. The developed biosensor extended the application of the CRISPR/Cas12a system for the sensitive detection of non-nucleic acid targets, providing a powerful tool in various fields such as environmental monitoring, food safety and clinical diagnosis.

2D Materials-Based Field-Effect Transistor Biosensors for Healthcare

The need for accurate point-of-care (POC) tools, driven by increasing demands for precise medical diagnostics and monitoring, has accelerated the evolution of biosensor technology. Integrable 2D materials-based field-effect transistor (2D FET) biosensors offer label-free, rapid, and ultrasensitive detection, aligning perfectly with current biosensor trends. Given these advancements, this review focuses on the progress, challenges, and future prospects in the field of 2D FET biosensors. The distinctive physical properties of 2D materials and recent achievements in scalable synthesis are highlighted that significantly improve the manufacturing process and performance of FET biosensors. Additionally, the advancements of 2D FET biosensors are investigated in fatal disease diagnosis and screening, chronic disease management, and environmental hazards monitoring, as well as their integration in flexible electronics. Their promising capabilities shown in laboratory trials accelerate the development of prototype products, while the challenges are acknowledged, related to sensitivity, stability, and scalability that continue to impede the widespread adoption and commercialization of 2D FET biosensors. Finally, current strategies are discussed to overcome these challenges and envision future implications of 2D FET biosensors, such as their potential as smart and sustainable POC biosensors, thereby advancing human healthcare.

Antibiotic residue detection by novel photoelectrochemical extended-gate field-effect transistor sensor

Residual antibiotics in the environment may pose threats to both ecological system and public health, necessitating the development of efficient analytical strategy for monitoring and control. This study proposes a photoelectrochemical extended-gate field-effect transistor (PEGFET) sensor for specific and sensitive detection of kanamycin. The sensor utilizes ITO glass as the extended gate electrode (photoelectrode) and titanium dioxide as the photosensitive material. It leverages the interaction between kanamycin and its corresponding aptamer to influence the ability of gold nanocluster to catalyze the oxidation of 3,3'-diaminobenzidine (DAB). This interaction results in different amounts of DAB precipitate on the photoelectrode surface, leading to gate voltage shift and source-drain current response. This sensing platform achieves trace detection of kanamycin with a limit of detection (LOD) at nM level and a wide linear detection range from 10 nM to 100 μM. The results demonstrate that the PEGFET with incorporated photoelectrochemical process can significantly enhance the sensitivity of traditional EGFET sensor, and the photoelectric signal originates from the change in electron transfer ability of the photoelectrode. The reported PEGFET with photo-responsive extended gate presents a new and promising structure in FET sensor design for enhanced detection performances in chemical and biological sensing.

Mitigating Antibiotic Resistance: The Utilization of CRISPR Technology in Detection

Antibiotics, celebrated as some of the most significant pharmaceutical breakthroughs in medical history, are capable of eliminating or inhibiting bacterial growth, offering a primary defense against a wide array of bacterial infections. However, the rise in antimicrobial resistance (AMR), driven by the widespread use of antibiotics, has evolved into a widespread and ominous threat to global public health. Thus, the creation of efficient methods for detecting resistance genes and antibiotics is imperative for ensuring food safety and safeguarding human health. The clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated proteins (Cas) systems, initially recognized as an adaptive immune defense mechanism in bacteria and archaea, have unveiled their profound potential in sensor detection, transcending their notable gene-editing applications. CRISPR/Cas technology employs Cas enzymes and guides RNA to selectively target and cleave specific DNA or RNA sequences. This review offers an extensive examination of CRISPR/Cas systems, highlighting their unique attributes and applications in antibiotic detection. It outlines the current utilization and progress of the CRISPR/Cas toolkit for identifying both nucleic acid (resistance genes) and non-nucleic acid (antibiotic micromolecules) targets within the field of antibiotic detection. In addition, it examines the current challenges, such as sensitivity and specificity, and future opportunities, including the development of point-of-care diagnostics, providing strategic insights to facilitate the curbing and oversight of antibiotic-resistance proliferation.

Overcoming Debye screening effect in field-effect transistors for enhanced biomarker detection sensitivity

Field-effect transistor (FET)-based biosensors not only enable label-free detection by measuring the intrinsic charges of biomolecules, but also offer advantages such as high sensitivity, rapid response, and ease of integration. This enables them to play a significant role in disease diagnosis, point-of-care detection, and drug screening, among other applications. However, when FET sensors detect biomolecules in physiological solutions (such as whole blood, serum, etc.), the charged molecules will be surrounded by oppositely charged ions in the solution. This causes the effective charge carried by the biomolecules to be shielded, thereby significantly weakening their ability to induce charge rearrangement at the sensing interface. Such shielding hinders the change of carriers inside the sensing material, reduces the variation of current between the source and drain electrodes of the FET, and seriously limits the sensitivity and reliability of the device. In this article, we summarize the research progress in overcoming the Debye screening effect in FET-based biosensors over the past decade. Here, we first elucidate the working principles of FET sensors for detecting biomarkers and the mechanism of the Debye screening. Subsequently, we emphasize optimization strategies to overcome the Debye screening effect. Finally, we summarize and provide an outlook on the research on FET biosensors in overcoming the Debye screening effect, hoping to help the development of FET electronic devices with high sensitivity, specificity, and stability. This work is expected to provide new ideas for next-generation biosensing technology.

Hypersensitive electrochemical sensor based on thermally annealed gold-silver alloy nanoporous matrices for the simultaneous determination of sulfathiazole and sulfamethoxazole residues in food samples

In this study, we have developed a novel, hypersensitive, and ultraselective electrochemical sensor containing thermally annealed gold-silver alloy nanoporous matrices (TA-Au-Ag-ANpM) integrated with f-MWCNTs-CPE and poly(l-serine) nanocomposites for the simultaneous detection of sulfathiazole (SFT) and sulfamethoxazole (SFM) residues in honey, beef, and egg samples. TA-Au-Ag-ANpM/f-MWCNTs-CPE/poly(l-serine) was characterized using an extensive array of analytical (UV-Vis, FT-IR, XRD, SEM, and EDX), and electrochemical (EIS, CV and SWV) techniques. It exhibited outstanding performance over a wide linear range, from 4.0 pM to 490 μM for SFT and 4.0 pM to 520 μM for SFM, with picomolar detection and quantification limits (0.53 pM and 1.75 pM for SFT, 0.41 pM and 1.35 pM for SFM, respectively). The sensor demonstrated exceptional repeatability, reproducibility, and anti-interference capability, with percentage recovery of 95.6-102.4% in food samples and RSD below 5%. Therefore, the developed sensor is an ideal tool to address the current antibiotic residue crisis in food sources.

Recent advances in two-dimensional materials for the diagnosis and treatment of neurodegenerative diseases

With the size of the aging population increasing worldwide, the effective diagnosis and treatment of neurodegenerative diseases (NDDs) has become more important. Two-dimensional (2D) materials offer specific advantages for the diagnosis and treatment of NDDs due to their high sensitivity, selectivity, stability, and biocompatibility, as well as their excellent physical and chemical characteristics. As such, 2D materials offer a promising avenue for the development of highly sensitive, selective, and biocompatible theragnostics. This review provides an interdisciplinary overview of advanced 2D materials and their use in biosensors, drug delivery, and tissue engineering/regenerative medicine for the diagnosis and/or treatment of NDDs. The development of 2D material-based biosensors has enabled the early detection and monitoring of NDDs via the precise detection of biomarkers or biological changes, while 2D material-based drug delivery systems offer the targeted and controlled release of therapeutics to the brain, crossing the blood-brain barrier and enhancing treatment effectiveness. In addition, when used in tissue engineering and regenerative medicine, 2D materials facilitate cell growth, differentiation, and tissue regeneration to restore neuronal functions and repair damaged neural networks. Overall, 2D materials show great promise for use in the advanced treatment of NDDs, thus improving the quality of life for patients in an aging population.

Microfabrication of engineered Lactococcus lactis biocarriers with genetically programmed immunorecognition probes for sensitive lateral flow immunoassay of antibiotic in milk and lake water

Micro/nanomaterials display considerable potential for increasing the sensitivity of lateral flow immunoassay (LFIA) by acting as 3D carriers for both antibodies and signals. The key to achieving high detection sensitivity depends on the probe's orientation on the material surface and its multivalent biomolecular interactions with targets. Here, we engineer Lactococcus lactis as the bacterial microcarrier (BMC) for a multivalent immunorecognition probe that was genetically programmed to display multifunctional components including a phage-screened single-chain variable fragment (scFv), an enhanced green fluorescent protein (eGFP), and a C-terminal peptidoglycan-binding domain (AcmA) anchored on BMC through the cell wall peptidoglycan. The innovative design of this biocarrier system, which incorporates a lab-on-a-chip microfluidic device, allows for the rapid and non-destructive self-assembly of the multivalent scFv-eGFP-AcmA@BMC probe, in which the 3D structure of BMC with a large peptidoglycan surface area facilitates the precisely orientated attachment and immobilization of scFv-eGFP-AcmA. This leads to a remarkable fluorescence aggregation amplification effect in LFIA, outperforming a monovalent 2D scFv-eGFP-AcmA probe for florfenicol detection. By designing a portable sensing device, we achieved an exceptionally low detection limit of 0.28 pg/mL and 0.21 pg/mL for florfenicol in lake water and milk sample, respectively. The successful microfabrication of this biocarrier holds potential to inspire innovative biohybrid designs for environment and food safety biosensing applications.

Unleashing the potential of tungsten disulfide: Current trends in biosensing and nanomedicine applications

The discovery of graphene ignites a great deal of interest in the research and advancement of two-dimensional (2D) layered materials. Within it, semiconducting transition metal dichalcogenides (TMDCs) are highly regarded due to their exceptional electrical and optoelectronic properties. Tungsten disulfide (WS2) is a TMDC with intriguing properties, such as biocompatibility, tunable bandgap, and outstanding photoelectric characteristics. These features make it a potential candidate for chemical sensing, biosensing, and tumor therapy. Despite the numerous reviews on the synthesis and application of TMDCs in the biomedical field, no comprehensive study still summarizes and unifies the research trends of WS2 from synthesis to biomedical applications. Therefore, this review aims to present a complete and thorough analysis of the current research trends in WS2 across several biomedical domains, including biosensing and nanomedicine, covering antibacterial applications, tissue engineering, drug delivery, and anticancer treatments. Finally, this review also discusses the potential opportunities and obstacles associated with WS2 to deliver a new outlook for advancing its progress in biomedical research.

A CRISPR/Cas12a-based fluorescence aptasensor for the rapid and sensitive detection of ampicillin

This study introduces CRISPR/Cas-based aptasensor for the highly sensitive and specific detection of the antibiotic, ampicillin. Ampicillin (AMPI) is a commonly used antibiotic for treating pathogenic bacteria and is additionally added to livestock feed in agriculture. This study can enable early detection of antibiotic residues, prevent their accumulation in the environment, and ensure compliance with food safety regulations. Herein, the aptasensor was developed with the CRISPR/Cas system by utilizing three different ampicillin-specific aptamers, each conjugated with a biotin at the 5'-end. The ssDNA activator was bound to the aptamers through complementary base pairings. The attraction of the aptamers to the ampicillin target released the bound ssDNA, causing the activation of the CRISPR/Cas system. The DNA reporter probe, labelled with Cy3 and a quencher, turns on the fluorescence signal when cleaved by the activated Cas12a through trans-cleavage measured using a fluorescence spectrophotometer at 590 nm. The fluorescence signal was linearly proportional to the ampicillin target concentration with a 0.01 nM limit of detection and a read-out time of 30 min. This aptasensor showed high sensitivity towards ampicillin even in the presence of other antibiotics. The method was also successfully implemented for ampicillin detection in spiked food samples.

Dielectrics for Two-Dimensional Transition-Metal Dichalcogenide Applications

Despite over a decade of intense research efforts, the full potential of two-dimensional transition-metal dichalcogenides continues to be limited by major challenges. The lack of compatible and scalable dielectric materials and integration techniques restrict device performances and their commercial applications. Conventional dielectric integration techniques for bulk semiconductors are difficult to adapt for atomically thin two-dimensional materials. This review provides a brief introduction into various common and emerging dielectric synthesis and integration techniques and discusses their applicability for 2D transition metal dichalcogenides. Dielectric integration for various applications is reviewed in subsequent sections including nanoelectronics, optoelectronics, flexible electronics, valleytronics, biosensing, quantum information processing, and quantum sensing. For each application, we introduce basic device working principles, discuss the specific dielectric requirements, review current progress, present key challenges, and offer insights into future prospects and opportunities.

An ultrasensitive FET biosensor based on vertically aligned MoS2 nanolayers with abundant surface active sites

Molybdenum disulfide (MoS₂) nanolayers are one of the most promising two-dimensional (2D) nanomaterials for constructing next-generation field-effect transistor (FET) biosensors. In this article, we report an ultrasensitive FET biosensor that integrates a novel format of 2D MoS₂, vertically-aligned MoS₂ nanolayers (VAMNs), as the channel material for label-free detection of the prostate-specific antigen (PSA). The developed VAMNs-based FET biosensor shows two distinctive advantages. First, the VAMNs can be facilely grown using the conventional chemical vapor deposition (CVD) method, permitting easy fabrication and potential mass device production. Second, the unique advantage of the VAMNs for biosensor development lies in its abundant surface-exposed active edge sites that possess a high binding affinity with thiol-based linkers, which overcomes the challenge of molecule functionalization on the conventional planar MoS₂ nanolayers. The high binding affinity between 11-mercaptoundecanoic acid and the VAMNs was demonstrated through experimental surface characterization and theoretical calculations via density functional theory. The FET biosensor allows rapid (within 20 min) and ultrasensitive PSA detection in human serum with simple operations (limit of detection: 800 fg mL^-1). This FET biosensor offers excellent features such as ultrahigh sensitivity, ease of fabrication, and short assay time, and thereby possesses significant potential for early-stage diagnosis of life-threatening diseases.