Magnetic antifouling material based ratiometric electrochemical biosensor for the accurate detection of CEA in clinical serum

Boronate crosslinking-based ratiometric electrochemical assay of glycated albumin

As a product of nonenzymatic glycation, glycated albumin (GA) is a promising serum marker for the short-term glycemic monitoring in patients with diabetes. On the basis of the boronate crosslinking (BCL)-enabled direct labeling of ferrocene (Fc) tags to the nonenzymatically glycated (NEG) sites, we report herein a novel aptamer-based ratiometric electrochemical (apt-REC) platform for the point-of-care (POC) assay of GA. This apt-REC platform is based on the recognition of GA proteins by the methylene blue (MB)-modified aptamer receptors and the labeling of the Fc tags to the NEG sites via the BCL. Using MB as the reference tag and Fc as the quantification tag, the ratio of the oxidation currents (i.e., IFc/IMB) can serve as the yardstick for the ratiometric assay of GA. Due to the presence of tens of the NEG sites, each GA protein can be labeled with tens of quantification tags, permitting the amplified assay in a simple, time-saving, and low-cost manner. The ratiometric signal exhibited a good linear response over the range from 0.1 to 100 μg/mL, with a detection limit of 45.5 ng/mL. In addition to the superior reproducibility and robustness, this apt-REC platform is highly selective (capable of discriminating GA against human serum albumin (HSA)) and applicable to GA assay in serum samples. Due to its low cost, high reproducibility and robustness, simple operation, and high sensitivity and selectivity, this apt-REC platform holds great promise in the POC assay of GA for diabetes management.

Signal amplification strategies in photoelectrochemical sensing of carcinoembryonic antigen

Early detection of cancer markers is critical for cancer diagnosis and cancer therapy since these markers may indicate cancer risk, incidence, and disease prognosis. Carcinoembryonic antigen (CEA) is a type of non-specific and broad-spectrum cancer biomarker commonly utilized for early cancer diagnosis. Moreover, it serves as an essential tool to assess the efficacy of cancer treatment and monitor tumor recurrence as well as metastasis, thus garnering significant attention for precise and sensitive CEA detection. In recent years, photoelectrochemical (PEC) techniques have emerged as prominent methods in CEA detection due to the advantages of PEC, such as simple equipment requirements, cost-effectiveness, high sensitivity, low interference from background signals, and easy of instrument miniaturization. Different signal amplification methods have been reported in PEC sensors for CEA analysis. Based on these, this article reviews PEC sensors based on various signal amplification strategies for detection of CEA during the last five years. The advantages and drawbacks of these sensors were discussed, as well as future challenges.

Polyaromatic Hydrocarbon-Functionalized 2D MXene-Based 3D Porous Antifouling Nanocomposite with Long Shelf Life for High-Performance Electrochemical Immunosensor Applications

Affinity-based electrochemical (AEC) biosensors have gained more attention in the field of point-of-care management. However, AEC sensing is hampered by biofouling of the electrode surface and degradation of the antifouling material. Therefore, a breakthrough in antifouling nanomaterials is crucial for the fabrication of reliable AEC biosensors. Herein, for the first time, we propose 1-pyrenebutyric acid-functionalized MXene to develop an antifouling nanocomposite to resist biofouling in the immunosensors. The nanocomposite consisted of a 3D porous network of bovine serum albumin cross-linked with glutaraldehyde with functionalized MXene as conductive nanofillers, where the inherited oxidation resistance property of functionalized MXene improved the electrochemical lifetime of the nanocomposite. On the other hand, the size-extruded porous structure of the nanocomposite inhibited the biofouling activity on the electrode surface for up to 90 days in real samples. As a proof of concept, the antifouling nanocomposite was utilized to fabricate a multiplexed immunosensor for the detection of C-reactive protein (CRP) and ferritin biomarkers. The fabricated sensor showed good selectivity over time and an excellent limit of detection for CRP and ferritin of 6.2 and 4.2 pg/mL, respectively. This research successfully demonstrated that functionalized MXene-based antifouling nanocomposites have great potential to develop high-performance and low-cost immunosensors.

Recent advances in the applications of DNA frameworks in liquid biopsy: A review

Cancer is one of the serious threats to public life and health. Early diagnosis, real-time monitoring, and individualized treatment are the keys to improve the survival rate and prolong the survival time of cancer patients. Liquid biopsy is a potential technique for cancer early diagnosis due to its non-invasive and continuous monitoring properties. However, most current liquid biopsy techniques lack the ability to detect cancers at the early stage. Therefore, effective detection of a variety of cancers is expected through the combination of various techniques. Recently, DNA frameworks with tailorable functionality and precise addressability have attracted wide spread attention in biomedical applications, especially in detecting cancer biomarkers such as circulating tumor cells (CTCs), exosomes and circulating tumor nucleic acid (ctNA). Encouragingly, DNA frameworks perform outstanding in detecting these cancer markers, but also face some challenges and opportunities. In this review, we first briefly introduced the development of DNA frameworks and its typical structural characteristics and advantages. Then, we mainly focus on the recent progress of DNA frameworks in detecting commonly used cancer markers in liquid-biopsy. We summarize the advantages and applications of DNA frameworks for detecting CTCs, exosomes and ctNA. Furthermore, we provide an outlook on the possible opportunities and challenges for exploiting the structural advantages of DNA frameworks in the field of cancer diagnosis. Finally, we envision the marriage of DNA frameworks with other emerging materials and technologies to develop the next generation of disease diagnostic biosensors.

Combining WO3@AuNPs with Poly(amidoamine) Allows Sensitive Electrochemical Detection of DR1 Based on Dual Signal Amplification

Down-regulator of transcription 1 (DR1) is considered as a biomarker of hashimoto's thyroiditis (HT), which is a risk factor for thyroid cancer. Here, a label-free electrochemical biosensor for DR1 detection was constructed based on polyamidoamine (PAMAM) polymer and the nanocomposite (WO3@AuNPs) composed of tungsten trioxide (WO3) and gold nanoparticles (AuNPs). WO3@AuNPs was obtained by combining monolayer WO3 nanosheets, which has high conductivity, and AuNPs. The modification of WO3@AuNPs can not only increase the conductivity of the electrode but also provide more active sites for signaling units, thus greatly improve the sensitivity of the sensor. The polymer PAMAM is biocompatible and non-immunogenic, and its end functional group can bind to the target molecules, providing them with more binding sites and thus improving the sensitivity of the sensor. Under optimal conditions, the label-free biosensor showed a good linear relationship between the logarithm of DR1 concentration and the impedance in the range of 10 fg ⋅ mL-1 to 100 ng ⋅ mL-1, with a detection limit as low as 0.3 fg ⋅ mL-1. Besides, this label-free electrochemical platform exhibited satisfactory selectivity and anti-interference capability in human serum samples. Therefore, this method has considerable potential in clinical detection of DR1.

Electrochemical biosensor based on PAMAM functionalized MXene nanoplatform for detection of folate receptor

The level of folate receptor (FR) has become one of the independent factors for measuring human tumor diseases. The precise quantification of FR is helpful for the early diagnosis and subsequent treatment of tumors. The modification of electrodes is a key issue in ensuring and enhancing the electrochemical biosensing ability. In this study, we in-situ synthesized a nanocomposite material with excellent conductivity and stability by grafting first-generation poly(amidoamine) dendrimers onto the MXene (Ti3C2TX) as the immobilized matrix (PAMAM@MXene). An electrochemical sensor was developed for FR monitor by loading the PAMAM@MXene on screen-printed carbon electrodes (SPCEs). Scanning electron microscopy (SEM) supported the effective synthesis of PAMAM@MXene. Under optimal conditions, the prepared sensor achieved the quantification of FR with a wide range of concentrations from 10 ng/mL to 1000 ng/mL with a detection limit (LOD) of 5.6 ng/mL. It also exhibited satisfactory selectivity, reproducibility, and stability, which provided the possibility for expanding new pathways in the detection of clinical FR.

The sensor applications for prostate and lung cancer biomarkers in terms of electrochemical analysis

Prostate and lung cancers are the most common types of cancer and affect a large part of the population around the world, causing deaths. Therefore, the rapid identification of cancer can profoundly impact reducing cancer-related death rates and protecting human lives. Significant resources have been dedicated to investigating new methods for early disease detection. Cancer biomarkers encompass various biochemical entities, including nucleic acids, proteins, sugars, small metabolites, cytogenetic and cytokinetic parameters, and whole tumor cells in bodily fluids. These tools can be utilized for various purposes, such as risk assessment, diagnosis, prognosis, treatment efficacy, toxicity evaluation, and predicting a return. Due to these versatile and critical purposes, there are widespread studies on the development of new, sensitive, and selective approaches for the determination of cancer biomarkers. This review illustrates the significant lung and prostate cancer biomarkers and their determination utilizing electrochemical sensors, which have the advantage of improved sensitivity, low cost, and simple analysis. Additionally, approaches such as improving sensitivity with nanomaterials and ensuring selectivity with MIPs are used to increase the performance of the sensor. This review aims to overview the most recent electrochemical biosensor applications for determining vital biomarkers of prostate and lung cancers in terms of nanobiosensors and molecularly imprinted polymer (MIP)-based biosensors.

A review of nanomaterials for biosensing applications

A biosensor is a device that reacts with the analyte to be analyzed, detects its concentration, and generates readable information, which plays an important role in medical diagnosis, detection of physiological indicators, and disease prevention. Nanomaterials have received increasing attention in the fabrication and improvement of biosensors due to their unique physicochemical and optical properties. In this paper, the properties of nanomaterials such as the size effect, optical and electrical properties, and their advantages in the field of biosensing are briefly summarized, and the application of nanomaterials can effectively improve the sensitivity and reduce the detection limit of biosensors. The advantages of commonly used nanomaterials such as gold nanoparticles (AuNPs), carbon nanotubes (CNTs), quantum dots (QDs), graphene, and magnetic nanobeads for biosensor applications are also reviewed. Besides, the two main types of biosensors using nanomaterials involved in their construction and their working principles are described, and the toxicity and biocompatibility of nanomaterials and the future direction of nanomaterial biosensors are discussed.

Ternary electrochemiluminescence quenching effects of CuFe2O4@PDA-MB towards self-enhanced Ru(dcbpy)32+ functionalized 2D metal-organic layer and application in carcinoembryonic antigen immunosensing

BACKGROUND

Carcinoembryonic antigen (CEA) is a significant glycosylated protein, and the unusual expression of CEA in human serum is used as a tumor marker in the clinical diagnosis of many cancers. Although scientists have reported many ways to detect CEA in recent years, such as electrochemistry, photoelectrochemistry, and fluorescence, their operation is complex and sensitivity is average. Therefore, finding a convenient method to accurately detect CEA is significance for the prevention of malignant tumors. With high sensitivity, quick reaction, and low background, electrochemiluminescence (ECL) has emerged as an essential method for the detection of tumor markers in blood.

RESULTS

In this work, a "signal on-off" ECL immunosensor for sensitive analysis of CEA ground on the ternary extinction effects of CuFe2O4@PDA-MB towards a self-enhanced Ru(dcbpy)32+ functionalized metal-organic layer [(Hf)MOL-Ru-PEI-Pd] was prepared. The high ECL efficiency of (Hf)MOL-Ru-PEI-Pd originated from the dual intramolecular self-catalysis, including intramolecular co-reaction between polyethylenimine (PEI) and Ru(dcbpy)32+. At the same time, loading Pd NPs onto (Hf)MOL-Ru-PEI could not only improve the electron transfer ability of (Hf)MOL-Ru-PEI, but also provide more active sites for the reaction of Ru(dcbpy)32+ and PEI. In the presence of CEA, CuFe2O4@PDA-MB-Ab2 efficiently quenches the excited states of (Hf)MOL-Ru-PEI-Pd by PDA, Cu2+, and methylene blue (MB) via energy and electron transfer, leading to an ECL signal decrease. Under optimal conditions, the proposed CEA sensing strategy showed satisfactory properties ranging from 0.1 pg mL-1 to 100 ng mL-1 with a detection limit of 20 fg mL-1.

SIGNIFICANCE

The (Hf)MOL-Ru-PEI-Pd and CuFe2O4@PDA-MB were prepared in this work might open up innovative directions to synthesize luminescence-functionalized MOLs and effective quencher. Besides, the ECL quenching mechanism of Ru(dcbpy)32+ by MB was successfully explained by the inner filter effect (ECL-IFE). At last, the proposed immunosensor exhibits excellent repeatability, stability, and selectivity, and may provide an attractive way for CEA and other disease markers determination.

Peptide-antifouling interface for monitoring β-amyloid based on electrochemiluminescence resonance energy transfer

In this study, a novel antifouling electrochemiluminescence (ECL) analytical platform has been developed for the highly sensitive quantification of β-amyloid (Aβ) peptides based on the ECL resonance energy transfer (ECL-RET) mechanism. Specifically, glassy carbon electrodes (GCE) were initially coated with graphite-phase carbon nitride (g-C3N4) nanosheets, followed by the electropolymerization of polyaniline (PANI) onto the electrode surface. Subsequently, a promising peptide motif candidate (COOH-CPPPPDKDKDKDKKLVFF) was immobilized onto the PANI-modified electrode, functioning as a critical component for both antifouling and specific recognition of full-length Aβ peptides. Furthermore, this peptide motif demonstrated inhibitory effects on Aβ aggregation and dissociation. Upon immobilization of the peptide motif, Aβ aptamer-CdS QDs were bound to the electrode surface through peptide-specific interactions with Aβ, thereby facilitating the highly sensitive ECL detection of Aβ. Under the optimal conditions, the proposed biosensor exhibited an Aβ detection range from 0.1 pM to 100 nM with a detection limit of 16.1 fM. As such, this innovative platform offers a straightforward approach to antifouling, quantification, and monitoring of Aβ concentrations in the blood samples.

Ultrasensitive Ratiometric Electrochemiluminescence Sensor with an Efficient Antifouling and Antibacterial Interface of PSBMA@SiO2-MXene for Oxytetracycline Trace Detection in the Marine Environment

The sensitivity and accuracy of electrochemiluminescence (ECL) sensors for detecting small-molecule pollutants in environmental water are affected not only by nonspecific adsorption of proteins and other molecules but also by bacterial interference. Therefore, there is an urgent need to develop an ECL sensor with antifouling and antibacterial functions for water environment monitoring. Herein, a highly efficient antifouling sensing interface (PSBMA@SiO2-MXene) based on zwitterionic sulfobetaine methacrylate (SBMA) antifouling nanospheres (NPs) and two-dimensional MXene nanosheets was designed for the sensitive detection of oxytetracycline (OTC), an antibiotic small-molecule pollutant. Specifically, SBMA with good hydrophilicity and electrical neutrality was connected to SiO2 NPs, thus effectively reducing protein and bacterial adsorption and improving stability. Second, MXene with a high specific surface area was selected as the carrier to load more antifouling NPs, which greatly improves the antifouling performance. Meanwhile, the introduction of MXene also enhances the conductivity of the antifouling interface. In addition, a ratio-based sensing strategy was designed to further improve the detection accuracy and sensitivity of the sensor by utilizing Au@luminol as an internal standard factor. Based on antifouling and antibacterial interfaces, as well as internal standard and ratiometric sensing strategies, the detection range of the proposed sensor was 0.1 ng/mL to 100 μg/mL, with a detection limit of 0.023 ng/mL, achieving trace dynamic monitoring of antibiotics in complex aqueous media.

Proximity Amplification-Enabled Electrochemical Analysis of Tumor-Associated Glycoprotein Biomarkers

Glycoproteins produced and secreted from specific cells and tissues are associated with several diseases and emerge as typical biomarkers to provide useful information in cancer diagnosis considering their abnormal expression levels. In this work, we design a universal method to achieve the accurate and sensitive analysis of tumor-associated glycoprotein biomarkers based on both carbohydrate recognition and protein recognition at the same protein surface. The byproduct of dual recognition-induced proximity amplification, pyrophosphate, triggers the disassembly of methylene blue-encapsulated metal-organic frameworks, MB@ZIF-90. As a result, methylene blue molecules are released to arouse amplified electrochemical responses for glycoprotein analysis. Experimental results demonstrate the high-accuracy analysis of carcinoembryonic antigen, a typical glycoprotein biomarker in cancer diagnosis, in a linear range of 0.001-100 ng mL-1 with a low limit of detection of 0.419 pg mL-1. The method also displays satisfactory specificity and recoveries in complex serum samples and proves good versatility by adopting two other tumor-associated glycoprotein biomarkers, α-fetoprotein and mucin-1, as the targets. Therefore, this work provides a valuable tool for the analysis of glycoprotein biomarkers, which may be of great potential in early warning of malignant tumors in clinical applications.

Biosensors for the detection of lung cancer biomarkers: A review on biomarkers, transducing techniques and recent graphene-based implementations

Lung cancer remains the leading cause of cancer-related death. In addition to chest X-rays and computerised tomography, the detection of cancer biomarkers serves as an emerging diagnostic tool for lung cancer. This review explores biomarkers including the rat sarcoma gene, the tumour protein 53 gene, the epidermal growth factor receptor, the neuron-specific enolase, the cytokeratin-19 fragment 21-1 and carcinoembryonic antigen as potential indicators of lung cancer. Biosensors, which utilise various transduction techniques, present a promising solution for the detection of lung cancer biomarkers. Therefore, this review also explores the working principles and recent implementations of transducers in the detection of lung cancer biomarkers. The transducing techniques explored include optical techniques, electrochemical techniques and mass-based techniques for detecting biomarkers and cancer-related volatile organic compounds. Graphene has outstanding properties in terms of charge transfer, surface area, thermal conductivity and optical characteristics, on top of allowing easy incorporation of other nanomaterials. Exploiting the collective merits of both graphene and biosensor is an emerging trend, as evidenced by the growing number of studies on graphene-based biosensors for the detection of lung cancer biomarkers. This work provides a comprehensive review of these studies, including information on modification schemes, nanomaterials, amplification strategies, real sample applications, and sensor performance. The paper concludes with a discussion of the challenges and future outlook of lung cancer biosensors, including scalable graphene synthesis, multi-biomarker detection, portability, miniaturisation, financial support, and commercialisation.

Hierarchically Structured and Highly Dispersible MOF Nanozymes Combining Self-Assembly and Biomineralization for Sensitive and Persistent Chemiluminescence Immunoassay

Metal-organic frameworks (MOF) are promising candidates for the construction of artificial nanozymes and have found applications in many fields. However, the preparation of nanosized MOF materials with high performance and good dispersibility is still a big challenge and is in great demand as signal labels for immunoassays. In this work, hierarchically structured and highly dispersible MOF nanoparticles were facilely prepared in a one-pot method. Self-assembled micelles from PEGylated hematin were used as structured templates to mediate the formation of zeolitic imidazole framework-8 (ZIF-8) nanoparticles in aqueous solution. The encapsulation of micelles in ZIF-8 frameworks produces well-dispersed nanoparticles and generates dual-confinement effects for catalytic hematin. Owing to the hierarchical structures, the formed MOF nanozymes show enhanced peroxidase-like activity and enable persistent chemiluminescence behaviors for the luminol system. Sandwich-type chemiluminescence immunoassays for carcinoembryonic antigen (CEA) were proposed using MOF nanozymes as signal labels, and good analytical performances were achieved. The combination of self-assembly and biomineralization may open new avenues for the development of MOF nanomaterials.

Facile preparation of Ru nanoassemblies for electrochemical immunoassay of carcinoembryonic antigen in clinical serum

Abnormal expression of carcinoembryonic antigen (CEA) can be used for early diagnosis of various cancers (e.g. colorectal cancer, cervical carcinomas, and breast cancer). In this work, using l-cysteine-ferrocene-Ruthenium nanocomposites (L-Cys-Fc-Ru) to immobilize secondary antibody (Ab₂) and Au nanoparticles (NPs) as the substrate to ensure accurate capture of primary antibody (Ab₁), a signal-on sandwich-like biosensor was constructed in the presence of CEA. Specifically, Ru nanoassemblies (NAs) were first prepared by a facile one-step solvothermal approach as signal amplifiers for the electrical signal of Fc. Based on specific immune recognition, as the increase of CEA concentration, the content of L-Cys-Fc-Ru-Ab₂ captured on the electrode surface also increased, thus the signal of Fc gradually increased. Therefore, the quantitative detection of CEA can be realized according to the peak current of Fc. After a series of experiments, it was found that the biosensor has a wide detection range from 1.0 pg mL^-1 to 100.0 ng mL^-1 and a low detection limit down to 0.5 pg mL^-1, as well as good selectivity, repeatability and stability. Furthermore, satisfactory results were also obtained for the determination of CEA in serums, which were comparable to commercial electrochemiluminescence (ECL) method. The developed biosensor shows great potential in clinical applications.

Recent Trends in Biosensing and Diagnostic Methods for Novel Cancer Biomarkers

Cancer is one of the major public health issues in the world. It has become the second leading cause of death, with approximately 75% of cancer deaths transpiring in low- or middle-income countries. It causes a heavy global economic cost estimated at more than a trillion dollars per year. The most common cancers are breast, colon, rectum, prostate, and lung cancers. Many of these cancers can be treated effectively and cured if detected at the primary stage. Nowadays, around 50% of cancers are detected at late stages, leading to serious health complications and death. Early diagnosis of cancer diseases substantially increases the efficient treatment and high chances of survival. Biosensors are one of the potential screening methodologies useful in the early screening of cancer biomarkers. This review summarizes the recent findings about novel cancer biomarkers and their advantages over traditional biomarkers, and novel biosensing and diagnostic methods for them; thus, this review may be helpful in the early recognition and monitoring of treatment response of various human cancers.

2D MXene-Based Biosensing: A Review

MXene emerged as decent 2D material and has been exploited for numerous applications in the last decade. The remunerations of the ideal metallic conductivity, optical absorbance, mechanical stability, higher heterogeneous electron transfer rate, and good redox capability have made MXene a potential candidate for biosensing applications. The hydrophilic nature, biocompatibility, antifouling, and anti-toxicity properties have opened avenues for MXene to perform in vitro and in vivo analysis. In this review, the concept, operating principle, detailed mechanism, and characteristic properties are comprehensively assessed and compiled along with breakthroughs in MXene fabrication and conjugation strategies for the development of unique electrochemical and optical biosensors. Further, the current challenges are summarized and suggested future aspects. This review article is believed to shed some light on the development of MXene for biosensing and will open new opportunities for the future advanced translational application of MXene bioassays.

Applications of electrochemical biosensors based on 2D materials and their hybrid composites in hematological malignancies diagnosis

Hematological malignancies encompass a wide variety of severe diseases that pose a serious threat to human health. Given the fact that hematological malignancies are difficult to treat due to their unpredictable and rapid deterioration and high rates of recurrence, growing attention has been paid to their early screening and diagnosis. However, developing a rapid and effective diagnostic tool featuring a noninvasive sampling technique is still extremely challenging. In recent years, novel nanomaterials-based electrochemical biosensors have attracted great interest because of such advantages as simple operation, low cost, fast response, etc. As a kind of rising nanomaterials, two-dimensional materials have excellent electronic and chemical properties, which have been proven to improve the performance of electrochemical biosensors. This review summarizes the applications of different types of electrochemical biosensors (nucleic acid sensors, immunosensors, aptamer biosensors, and cytosensors) based on two-dimensional materials in the detection of biological molecules related to hematological malignancies. Two-dimensional materials-based electrochemical biosensors designed for the diagnosis of leukemia could rapidly detect the target biomolecules at a trace level and show great merits such as wide linear range, low detection limit, high sensitivity, excellent selectivity, and cost-effectiveness. In addition, these biosensors have also achieved satisfactory results in the diagnosis of lymphoma and multiple myeloma. Thus, two-dimensional materials-based electrochemical biosensors are attractive for the early diagnosis of hematological malignancies in clinical practice. Nevertheless, more efforts are still required to further improve the performance of electrochemical biosensors. In this review, we propose the possible main concerns in the design of future two-dimensional materials-based electrochemical biosensors, involving the development of sensors for synchronous detection of diverse target biomolecules, the exploration of other superior two-dimensional materials, the simplification of the sensors fabrication process, the construction of new hybrid structures and how to avoid possible environmental issues.

Ultrahighly Sensitive Sandwich-Type Electrochemical Immunosensor for Selective Detection of Tumor Biomarkers

Herein, a novel sandwich-type immunosensor was designed using Pt nanoparticle-decorated SnS₂ nanoplates (Pt@SnS₂) as a matrix and N,B-doped Eu MOF (N,B-Eu MOF) nanospheres as a signal amplifier. In Pt@SnS₂, Pt nanoparticles (NPs) enhance the surface electron transport capability and electrochemiluminescence (ECL) performance of SnS₂ nanoplates. The dual "antenna" effect of 5-boronoisophthalic acid (5-bop) and 5-nitroisophthalic acid (5-nop) enables the N,B-Eu MOFs to show very good ECL performance at the cathode. In the presence of the target carcinoembryonic antigen (CEA), the sandwich-type immunosensor provides specific immune responses, and the ECL signal of the immunosensor is greatly amplified by the signal probe N,B-Eu MOFs. In view of the above, the immunosensor was successfully applied for highly sensitive and selective detection of CEA with a detection limit of 0.06 pg·mL^-1. This sensor exhibits high sensitivity and specificity, excellent stability, good reproducibility, and good practicability in real human serum.

Electrochemical aptasensor based on Ce3NbO7/CeO2@Au hollow nanospheres by using Nb.BbvCI-triggered and bipedal DNA walker amplification strategy for zearalenone detection

Herein, an electrochemical aptasensor combining Nb.BbvCI-triggered bipedal DNA walking strategy was constructed for ultrasensitive assay of zearalenone (ZEN). The aptasensor used Ce₃NbO₇/CeO₂ @Au hollow nanospheres as electrode modification material and PdNi@MnO₂/MB as the signal label. Importantly, the Ce₃NbO₇/CeO₂ synthesized by hydrothermal method were combined with Au nanoparticles and applied to the electrode surface. The as-prepared Ce₃NbO₇/CeO₂ @Au possessed a large surface area, excellent electrical conductivity, stability and more binding sites. PdNi@MnO₂ with high specific surface area and porosity combined with molecule methylene blue (MB) was introduced into electrodes as the signal label. The proposed aptasensor utilized the advantages of specific recognition of aptamers and target molecules to release bipedal DNA walker (w-DNA), and then the w-DNA was triggered by Nb.BbvCI and entered the cycle to release more signal probes. The feasibility of this strategy was recorded by the differential pulse voltammetry (DPV) method. Under the optimized conditions, the electrochemical aptasensor exhibited a wide linear dynamic range from 1 × 10^-4 to 1 × 10³ ng mL^-1 with a low detection limit of 4.57 × 10^-6 ng mL^-1. Moreover, the aptasensor had high selectivity, good stability, excellent repeatability and provided an effective method for the trace detection of ZEN in real samples.

Dual-signal amplified electrochemical biosensor based on eATRP and PEI for early detection of lung cancer

Carcinoembryonic antigen (CEA), a lung cancer marker with high sensitivity and specificity, plays vital roles in the early diagnosis of lung cancer. In this paper, an electrochemical biosensor for highly sensitive detection of CEA was constructed, which based on dual signal amplification of electrically mediated atom transfer radical polymerization (eATRP) and polyethyleneimine (PEI) for the first time. Firstly, CEA was captured in a specific recognition manner with CEA aptamer 1 (Apt1), which self-assembled on the electrode via "Au-S" bond. After that, CEA aptamer 2-PEI (Apt2-PEI) was recognized by CEA to form an Apt-antigen-Apt sandwich structure. Next, multiple initiation sites were introduced for the eATRP reaction by the amide reaction. Finally, numerous electroactive monomers, ferrocene methacrylate (FMMA), were grafted onto the modified electrode by eATRP. Under the optimized conditions, there was a wide linear detection range of 10^-3 ∼ 10² ng·mL^-1, and the limit of detection (LOD) was 70.17 fg·mL^-1. Compared to other reported sensors, this electrochemical biosensor used a simpler and more environmentally friendly eATRP, and the use of PEI increased the electron transfer rate. Moreover, the biosensor showed superior analytical performance in the clinical serums and has great promise for early lung cancer diagnosis applications.

Supramolecular Enzymatic Labeling for Aptamer Switch-Based Electrochemical Biosensor

Here we report a novel labeling strategy for electrochemical aptasensors based on enzymatic marking via supramolecular host–guest interactions. This approach relies on the use of an adamantane-modified target-responsive hairpin DNA aptamer as an affinity bioreceptor, and a neoglycoconjugate of β-cyclodextin (CD) covalently attached to a redox enzyme as a labeling element. As a proof of concept, an amperometric aptasensor for a carcinoembryonic antigen was assembled on screen-printed carbon electrodes modified with electrodeposited fern-like gold nanoparticles/graphene oxide and, by using a horseradish peroxidase-CD neoglycoenzyme as a biocatalytic redox label. This aptasensor was able to detect the biomarker in the concentration range from 10 pg/mL to 1 ng/mL with a high selectivity and a low detection limit of 3.1 pg/mL in human serum samples.

Ultrasensitive SARS-CoV-2 diagnosis by CRISPR-based screen-printed carbon electrode

Early and accurate diagnosis of SARS-CoV-2 was crucial for COVID-19 control and urgently required ultra-sensitive and rapid detection methods. CRISPR-based detection systems have great potential for rapid SARS-CoV-2 detection, but detecting ultra-low viral loads remains technically challenging. Here, we report an ultrasensitive CRISPR/Cas12a-based electrochemical detection system with an electrochemical biosensor, dubbed CRISPR-SPCE, in which the CRISPR ssDNA reporter was immobilized onto a screen-printed carbon electrode. Electrochemical signals are detected due to CRISPR cleavage, giving enhanced detection sensitivity. CRISPR-SPCE enables ultrasensitive SARS-CoV-2 detection, reaching as few as 0.27 copies μL⁻¹. Moreover, CRISPR-SPCE is also highly specific and inexpensive, providing a fast and simple SARS-CoV-2 assay.