Versatility and stability of melamine foam-based biosensors (f-ELISA) using antibodies, nanobodies, and peptides as sensing probes.

Macroporous three-dimensional (3D) framework structured melamine foam-based Enzyme-Linked Immunosorbent Assay (f-ELISA) biosensors were developed for rapid, reliable, sensitive, and on-site detection of trace amount of biomolecules and chemicals. Various ligands can be chemically immobilized onto the melamine foam, which brings in the possibility of working with antibodies, nanobodies, and peptides, respectively, as affinity probes for f-ELISA biosensors with improved stability. Different chemical reagents can be used to modify the foam materials, resulting in varied reactivities with antibodies, nanobodies, and peptides. As a result, the f-ELISA sensors produced from these modified foams exhibit varying levels of sensitivity and performance. This study demonstrated that the chemical reagents used for immobilizing antibodies, nanobodies, and peptides could affect the sensitivities of the f-ELISA sensors, and their storage stabilities under different temperatures varied depending on the sensing probes used, with f-ELISA sensors employing nanobodies as probes exhibiting the highest stability. This study not only showcases the versatility of the f-ELISA system but also opens new avenues for developing cost-effective, portable, and user-friendly diagnostic tools with optimized sensitivity and stability.

Reagent-free anti-fouling electrochemical immunosensor based on AL-BSA/AuNPs/PANI coating for the point-of-care detection of C-reactive protein in plasma and whole blood.

Developing the portable CRP detection technologies that are suitable for point-of-care (POC) and primary care management is of utmost importance, and advancing the electrochemical immunosensors hold promise for POC implementation. Nevertheless, non-specific adsorption of numerous interfering proteins in complex biological media contaminates immunosensors, thereby restricting the reliability in detection efficacy. In this study, a three-dimensional flower-leaf shape amyloid bovine serum albumin/gold nanoparticles/polyaniline (AL-BSA/AuNPs/PANI) coating on the surface of the electrode was developed, which demonstrated strong anti-adsorption properties against bovine serum albumin, plasma, and cells. The immunosensor exhibited a good linear relationship to CRP response, featuring a detection limit of 0.09 µg/mL, consistent with clinical reference range. In addition, the CRP immunosensor demonstrated excellent specificity in other inflammation-related proteins and commendable anti-interference performance for CRP detection in plasma and whole blood tests. Importantly, by combining the development of a USB flash disk-type portable electrochemical workstation with a reagent-free mode, the developed CRP electrochemical immunosensor delivered ideal results in clinical samples. The anti-fouling performance, sensitivity and specificity of the immunosensor, as well as its flexible test modes in clinical samples, provide important scientific basis for developing POC detection technologies of vital biomarkers in complex biological media.

Aggregation-induced electrochemiluminescence based on intramolecular charge transfer and twisted molecular conformation for label-free Immunoassay.

Organic emitters with exceptional properties exhibit significant potential in the field of aggregation-induced electrochemiluminescence (AIECL); however, their practicality is impeded by limited ECL efficiency (ΦECL). This paper investigates a novel type of AIECL emitter (BDPPA NPs), where an efficient intramolecular charge transfer (ICT) effect and highly twisted conformation contribute to a remarkable enhancement of ECL. The ICT effect reduces the electron transfer path, while the twisted conformation effectively restricts π-π stacking and intramolecular motions. Intriguingly, compared to the standard system of [Ru(bpy)32+]/TPrA, bright emissions with up to 54 % ΦECL were achieved, enabling direct visual observation of ECL through the co-reactant route. The label-free immunosensor exhibited distinguished performance in detecting SARS-CoV-2 N protein across an exceptionally wide linear range of 0.001-500 ng mL-1, with a remarkably low detection limit of 0.28 pg mL-1. Furthermore, this developed ECL platform exhibited excellent sensitivity, specificity, and stability characteristics, providing an efficient avenue for constructing platforms for bioanalysis and clinical diagnosis analysis.

Sensitive electrochemical immunosensor for rapid detection of Salmonella in milk using polydopamine/CoFe-MOFs@Nafion modified gold electrode.

Food contaminated by pathogenic bacteria poses a serious threat to human health. Consequently, we used Salmonella as a model and developed an electrochemical immunosensor based on a polydopamine/CoFe-MOFs@Nafion nanocomposite for the detection of Salmonella in milk. The CoFe-MOFs exhibit good stability, large specific surface area, and high porosity. However, after modification on the electrode surface, they were prone to detachment. This issue was effectively mitigated by incorporating Nafion into the nanocomposite. A polydopamine (PDA) film was deposited onto the surface of CoFe-MOFs@Nafion through cyclic voltammetry (CV), accompanied by an investigation into the polymerization mechanism of the PDA film. PDA contains a substantial number of quinone functional groups, which can covalently bind to amino or sulfhydryl groups via Michael addition reaction or Schiff base reaction, thereby immobilizing anti-Salmonella antibodies onto the modified electrode surface. Under the optimal experimental conditions, the Salmonella concentration exhibited a good linear relationship within the range of 1.38 × 102 to 1.38 × 108 CFU mL-1, with a detection limit of 1.38 × 102 CFU mL-1. Furthermore, the constructed immunosensor demonstrated good specificity, stability, and reproducibility, offering a novel approach for the rapid detection of foodborne pathogens.

Portable smartphone-assisted amperometric immunosensor based on CoCe-layered double hydroxide for rapidly immunosensing erythromycin.

Herein, we have manufactured a newly designed bifunctional impedimetric and amperometric immunosensor for rapidly detecting erythromycin (ERY) in complicated environments and food stuffs. For this, bimetallic cobalt/cerium-layered double hydroxide nanosheets (CoCe-LDH NSs), which was derived from Co-based zeolite imidazole framework via the structure conversion, was simultaneously utilized as the bioplatform for anchoring the ERY-targeted antibody and for modifying the gold and screen printed electrode. Basic characterizations revealed that CoCe-LDH NSs was composed of mixed metal valences, enrich redox, and abundant oxygen vacancies, facilitating the adhesion on the electrode, the antibody adsorption, and the electron transfers. The manufactured impedimetric and amperometric immunosensor based on CoCe-LDH has showed the comparable sensing performance, having a wide linear detection range from 1.0 fg mL-1 to 1.0 ng mL-1 with the ultralow detection limit toward ERY. Also, the portable, visualized, and efficient analysis of ERY was then attained at the smartphone-assisted CoCe-LDH-based SPE.

Efficient CdIn2S4/MgIn2S4 heterojunction for ultrasensitive detection of lung cancer marker neuron-specific enolase.

In this work, a photoelectrochemical (PEC) immunosensor was constructed for the ultrasensitive detection of lung cancer marker neuron-specific enolase (NSE) based on a microflower-like heterojunction of cadmium indium sulfide and magnesium indium sulfide (CdIn2S4/MgIn2S4, CMIS) as photoactive material. Specifically, the well-matched energy level structure and narrow energy level gradients between CdIn2S4 and MgIn2S4 could accelerate the separation of electron-hole (e--h+) pairs in the CMIS heterojunction to enhance the photocurrent of CMIS, which was increased 5.5 and 80 times compared with that of single CdIn2S4 and MgIn2S4, respectively. Meanwhile, using CMIS as photoactive material, increasing the biocompatibility by dropping Pt NPs on the surface of CMIS to immobilize the antibody through Pt-N bond. Fe3O4-Ab2, acting as the quencher, competitively consumes electron donors and absorbs light, leading to photocurrent quenching. With the increasing of quencher, the photocurrent decreased. Hence, the developed "signal-off" PEC immunosensor realized the trace detection of NSE within the range from 1.0 fg/mL to 10 ng/mL with a low detection limit of 0.34 fg/mL. This strategy provided a new perspective for establishing ternary metal sulfide heterojunction to construct PEC immunosensor for sensitive detection of disease biomarkers.

A photoelectrochemical sensor based on In2S3/AgInS2 in situ Z-type heterojunction with "photo-modulated interface charge" for sensitive detection of Programmed Death-Ligand 1.

The construction of heterostructure photoelectrodes can enhance the performance of photoelectrochemical (PEC) sensors. However, it is still a critical challenge to achieve efficient transfer of interface carriers. In this paper, we propose a strategy of "photo-modulated interface charge" to design a PEC sensor based on a hollow hexagonal tubular In2S3/AgInS2 in situ Z-type heterojunction for the susceptible detection of Programmed Death-ligand 1 (PD-L1). The hollow structured In2S3/AgInS2 is ingeniously synthesized employing indium-sourced MIL-68 as a sacrificial template and in situ cation exchange technique. This composite material has close contact interfaces due to in situ growth, which facilitates the spontaneous establishment of a robust and stable built-in electric field between the interfaces. Moreover, the inner cavity structure promotes multiple light refractions and scatterings, significantly enhancing light trapping capability. Under the influence of both light irradiation and electric field force, the migration direction of the interfacial charge is reversed, forming a Z-transfer path, which effectively delays the compounding of the electron-hole pairs (e-/h+) and further improves the sensitivity of the sensor. The minimum detection threshold of the PEC sensor is 26.58 fg/mL, and the feasibility of real samples is investigated, providing new insights for early diagnosis and prognostic treatment of diseases.

Effect of nanoarray density on enhanced electron transfer efficiency and analytical sensitivity for electrochemical immunosensors.

The fabrication of ordered nanoarray electrode (NAE) using UV imprinting and their application as electrochemical (EC) immunosensor is described in this study. Especially, the influence of the array density factors on the performance of NAE was characterized electrochemically and compared with flat-electrode. Low-density (hole: 200 nm, hole space = 600 nm), medium-density (hole: 200 nm, hole space = 400 nm), and high-density NAE (hole: 200 nm, hole space = 200 nm) which have the same active area were fabricated and their redox cycling was compared with empirical results. We observed that the high-density is the optimum NAE exhibiting the lowest charge transfer resistance and the highest redox cycling performance among all NAEs. Finally, to observe the effect of their EC performance as biosensor, an EC immunoassay was performed using Interleukine-6 (IL-6), and high-density NAE has lowest a low limit of detection (LOD) of 0.45 pg/mL compared with other NAEs (medium-density: 3.91 pg/mL, low-density: 5.87 pg/mL).

A novel sandwich electrochemical immunosensor utilizing customized template and phosphotungstate catalytic amplification for CD44 detection.

A sandwich-type electrochemical immunosensor was proposed for the ultra-sensitive detection of CD44, a potential biomarker for breast cancer. In this design, a customized template-based ionic liquid (1-butyl-2,3-dimethylimidazolium tetrafluoroborate) carbon paste electrode (CILE) served as the sensing platform, and thionine/Au nanoparticles/covalent-organic frameworks (THI/Au/COF) were used as the signal label. Moreover, an enzyme-free signal amplification strategy was introduced by involving H2O2 and phosphotungstate (PW12) with peroxidase-like activity. Under optimized conditions, the linear range is as wide as six orders of magnitude, and the detection limit is as low as 0.71 pg mL-1 (estimated based on S/N = 3). Average recoveries range from 98.16 %-100.1 %, with a relative standard deviation (RSD) of 1.42-8.27 % in mouse serum, and from 98.44 %-99.06 %, with an RSD of 1.14-4.84 % (n = 3) in artificial saliva. Furthermore, the immunosensor exhibits excellent specificity toward CD44, good stability, and low cost, indicating great potential for application in clinical trials.

Development and application of bisphenol S electrochemical immunosensor and iridium oxide nanoparticle-based lateral flow immunoassay.

Bisphenol S (BPS) is a common pollutant in the environment and has posed a potential threat to aquatic animals and human health. To accurately assess the pollution level and ecological risk of BPS, there is an urgent need to establish simple and sensitive detection methods for BPS. In this study, BPS complete antigen was successfully prepared by introducing methyl 4-bromobutyrate and coupling bovine serum albumin (BSA). The monoclonal antibody against BPS (anti-BPS mAb) with high affinity (1: 256,000) was developed based on the BPS complete antigen, which showed low cross-reactivity with BPS structural analogues. Then, an electrochemical immunosensor was constructed to detect BPS using multi-walled carbon nanotubes and gold nanoflower composites as signal amplification elements and using anti-BPS mAb as the probe. The electrochemical immunosensor had a linear range from 1 to 250 ng⋅mL-1 and a limit of detection (LOD) down to 0.6 ng⋅mL-1. Additionally, a more stable and sensitive lateral flow immunoassay (LFIA) for BPS was developed based on iridium oxide nanoparticles, with a visual detection limit of 1 ng⋅mL-1, which was 10 times lower than that of classical Au-NPs LFIA. After evaluation of their stability and specificity, the reliability of these two methods were further validated by measuring BPS concentrations in the water and fish tissues. Thus, this study provides sensitive, robust and rapid methods for the detection of BPS in the environment and organisms, which can provide a methodological reference for monitoring environmental contaminants.

Functionalized N95 Face Mask with a Chemical-Free Paper-Based Collector for Exhaled Breath Analysis: SARS-CoV-2 Detection with a Printed Immunosensor as a Case Study.

Exhaled breath electrochemical sensing is a promising biomedical technology owing to its portability, painlessness, cost-effectiveness, and user-friendliness. Here, we present a novel approach for target analysis in exhaled breath by integrating a comfortable paper-based collector into an N95 face mask, providing a universal solution for analyzing several biomarkers. As a model analyte, we detected SARS-CoV-2 spike protein from the exhaled breath by sampling the target analyte into the collector, followed by its detection out of the N95 face mask using a magnetic bead-based electrochemical immunosensor. This approach was designed to avoid any contact between humans and the chemicals. To simulate human exhaled breath, untreated saliva samples were nebulized on the paper collector, revealing a detection limit of 1 ng/mL and a wide linear range of 3.7-10,000 ng/mL. Additionally, the developed immunosensor exhibited high selectivity toward the SARS-CoV-2 spike protein, compared to other airborne microorganisms, and the SARS-CoV-2 nucleocapsid protein. Accuracy assessments were conducted by analyzing the simulated breath samples spiked with varying concentrations of SARS-CoV-2 spike protein, resulting in satisfactory recovery values (ranging from 97 ± 4 to 118 ± 1%). Finally, the paper-based hybrid immunosensor was successfully applied for the detection of SARS-CoV-2 in real human exhaled breath samples. The position of the collector in the N95 mask was evaluated as well as the ability of this paper-based analytical tool to identify the positive patient.

Development of an amperometric biosensor for the detection of Bacillus anthracis spores.

INTRODUCTION: Due to most likely use of Bacillus anthracis in biological terrorism agents, the rapid and sensitive detection of its spores is crucial in both taking prophylactic measures and proper treatment. This study aimed to develop an amperometric electrochemical immunosensor for the detection of B. anthracis spores. METHODS: A new amperometric biosensor was designed using a combination of magnetic beads and multiplex screen-printed electrodes. This method measures changes in current intensity resulting from oxidation and reduction in the working electrode directly to spore concentrations. RESULTS: A standard curve was formed to test the number of live spores between 2 × 102-2 × 104 spores/ml concentrations. LOD and LOQ values were found to be 92 and 272 spores/ml, respectively. No cross-reactions were seen for Bacillus subtilis, Bacillus cereus and Bacillus thuringiencis spores. CONCLUSIONS: It is shown that the designed Anthrax immunosensor has high sensitivity and selectivity with rapid detection results.

Ultrasensitive carbon nanotube-bridged MXene conductive network arrays for one-step homogeneous electrochemical immunosensing of tumor markers.

Developing non-passivating and fully integrated electrode arrays for point-of-care testing of carcinoembryonic antigen (CEA) is crucial, as the serum level of CEA is closely associated with colorectal cancer. Herein, we propose a simple, low-cost, and eco-friendly template-assisted filtration method for the scalable preparation of carbon nanotube-bridged Ti3C2Tx MXene (MX@CNT) electrode arrays with a conductive network. Furthermore, we fabricate a homogeneous electrochemical (HEC) sensor for CEA detection by integrating a magnetic-bead-based alkaline phosphatase-linked immunoassay (MB-aElisa), which enables the in-situ generation of the electroactive substance 1-naphthol (1-NP). Benefiting from the unique electrochemical characteristics of a MX@CNT electrode array, such as ultra-low background signal and superior electrocatalytic activity towards the hydrolyzed 1-NP, the MB-aElisa-based HEC sensor specifically measures CEA within a detection range spanning from 0.005 to 1.0 ng mL-1, achieving a detection limit of 1.6 pg mL-1. Subsequently, this biosensing prototype is successfully utilized for the detection of CEA in serum specimens obtained from colorectal cancer patients. More importantly, the integration of MB-aElisa with a MX@CNT electrode array not only marks a significant advancement but also enables the creation of a one-step homogeneous electrochemical immunosensing platform, serving as a paradigm for the highly sensitive and selective measurement of trace tumor markers in complex biological samples.

Anti-IgG Doped Melanin Nanoparticles Functionalized Quartz Tuning Fork Immunosensors for Immunoglobulin G Detection: In Vitro and In Silico Study.

The quartz tuning fork (QTF) is a promising instrument for biosensor applications due to its advanced properties such as high sensitivity to physical quantities, cost-effectiveness, frequency stability, and high-quality factor. Nevertheless, the fork's small size and difficulty in modifying the prongs' surfaces limit its wide use in experimental research. Our study presents the development of a QTF immunosensor composed of three active layers: biocompatible natural melanin nanoparticles (MNPs), glutaraldehyde (GLU), and anti-IgG layers, for the detection of immunoglobulin G (IgG). Frequency shifts of QTFs after MNP functionalization, GLU activation, and anti-IgG immobilization were measured with an Asensis QTF F-master device. Using QTF immunosensors that had been modified under optimum conditions, the performance of QTF immunosensors for IgG detection was evaluated. Accordingly, a finite element method (FEM)-based model was produced using the COMSOL Multiphysics software program (COMSOL License No. 2102058) to simulate the effect of deposited layers on the QTF resonance frequency. The experimental results, which demonstrated shifts in frequency with each layer during QTF surface functionalization, corroborated the simulation model predictions. A modelling error of 0.05% was observed for the MNP-functionalized QTF biosensor compared to experimental findings. This study validated a simulation model that demonstrates the advantages of a simulation-based approach to optimize QTF biosensors, thereby reducing the need for extensive laboratory work.

Cooperative amplification of Prussian blue as a signal indicator and functionalized metal-organic framework-based electrochemical biosensor for an ultrasensitive HE4 assay.

Human epididymis protein 4 (HE4), a diagnostic biomarker of ovarian cancer, is crucial for monitoring the early stage of the disease. Hence, it is highly important to develop simple, inexpensive, and user-friendly biosensors for sensitive and quantitative HE4 assays. Herein, a new sandwich-type electrochemical immunosensor based on Prussian blue (PB) as a signal indicator and functionalized metal-organic framework nanocompositesas efficient signal amplifiers was fabricated for quantitative analysis of HE4. In principle, ketjen black (KB) and AuNPs modified on TiMOF (TiMOF-KB@AuNPs) could accelerate electron transfer on the electrode surface and act as a matrix for the immobilization of antibodies via cross-linking to improve the determination sensitivity. The PB that covalently binds to labeled antibodies endows the biosensors with intense electrochemical signals. Furthermore, the concentration of HE4 could be indirectly detected by monitoring the electroactivity of PB. Benefiting from the high signal amplification ability of the PB and MOF nanocomposites, this strategy displayed a wide linear range (0.1-80 ng mL-1) and a lower detection limit (0.02 ng mL-1). Hence, this study demonstrated great promise for application in clinical ovarian cancer diagnosis and treatment, and provided a new platform for detecting other cancer biomarkers.

A disposable electrochemical magnetic immunosensor for the rapid and sensitive detection of 5-formylcytosine and 5-carboxylcytosine in DNA.

5-formylcytosine (5 fC) and 5-carboxylcytosine (5caC) serve as key intermediates in DNA demethylation process with significant implications for gene regulation and disease progression. In this study, we introduce a novel electrochemical sensing platform specifically designed for the sensitive and selective detection of 5 fC and 5caC in DNA. Protein A-modified magnetic beads (ProtA-MBs) coupled with specific antibodies facilitate the immunorecognition and enrichment of these modified bases. Signal amplification is achieved through several chemical reactions involving the interaction between N3-kethonaxl and guanine, copper-free click chemistry for the attachment of dibenzocyclooctyne (DBCO)-Biotin, and the subsequent recognition by streptavidin-conjugated horseradish peroxidase (SA-HRP). The assay's readout is performed on a disposable laser-induced graphene (LIG) electrode, modified with the bead-antibody-DNA complex in a magnetic field, and analyzed using differential pulse voltammetry in a system employing hydroquinone (HQ) as the redox mediator and H2O2 as the substrate. This immunosensor displayed excellent sensitivity, with detection limits of 14.8 fM for 5 fC across a 0.1-1000 pM linear range and 87.4 fM for 5caC across a 0.5-5000 pM linear range, and maintained high selectivity even in the presence of interferences from other DNA modifications. Successful application in quantifying 5 fC and 5caC in genomic DNA from cell extracts, with recovery rates between 97.7% to 102.9%, underscores its potential for clinical diagnostics. N3-kethoxal was used for the first time in an electrochemical sensor. This work not only broadens the toolkit for detecting DNA modifications but also provides a fresh impetus for the development of point-of-care testing (POCT) technologies.

Rapid and sensitive detection of heart-type fatty acid binding protein using aggregation-induced emission nanoparticles on digital microfluidics workstation.

Early and rapid diagnostic of acute myocardial infarction (AMI) during its developing stage is crucial due to its high fatality rate. Heart-type fatty acid binding protein (h-FABP) is an ideal biomarker for the quantitative diagnosis of AMI, surpassing traditional markers such as myoglobin, creatine phosphokinase-MB, and troponin in terms of sensitivity, specificity, and prognostic value. To obtain diagnostic and prognostic information, a precise and fully quantitative measurement of h-FABP is essential, typically achieved through an immunosorbent assay like the enzyme-linked immunosorbent assay. Nevertheless, this method has several limitations, including extended detection time, complex assay procedures, the necessity for skilled technicians, and challenges in implementing automated detection. This research introduces a novel biosensor, utilizing aggregation-induced emission nanoparticles (AIENPs) and integrated with a digital microfluidic (DMF) workstation, designed for the sensitive, rapid, and automated detection of h-FABP in low-volume serum samples. AIENPs and magnetic beads in nanoscale were served as the capture particles and the fluorescent probe, which were linked covalently to anti-h-FABP antibodies respectively. The approach was based on a sandwich immunoassay and performed on a fully automated DMF workstation with assay time by 15 min. We demonstrated the determination of h-FABP in serum samples with detection limit of 0.14 ng/mL using this biosensor under optimal condition. Furthermore, excellent correlations (R2 = 0.9536, n = 50) were obtained between utilizing this biosensor and commercialized ELISA kits in clinical serum detecting. These results demonstrate that our flexible and reliable biosensor is suitable for direct integration into clinical diagnostics, and it is expected to be promising diagnostic tool for early detection and screening tests as well as prognosis evaluation for AMI patients.

One-step detection of procollagen type III N-terminal peptide as a fibrosis biomarker using fluorescent immunosensor (quenchbody).

BACKGROUND: Procollagen type III N-terminal peptide (P-III-NP) is a fibrosis biomarker associated with liver and cardiac fibrosis. Despite the value of P-III-NP as a biomarker, its analysis currently relies on enzyme-linked immunosorbent assays (ELISA) and radioimmunoassays (RIA), which require more than 3 h. To facilitate early diagnosis and treatment through rapid biomarker testing, we developed a one-step immunoassay for P-III-NP using a quenchbody, which is a fluorescence-labeled immunosensor for immediate signal generation. RESULTS: To create quenchbodies, the total mRNA of P-III-NP antibodies was extracted from early-developed hybridoma cells, and genes of variable regions were obtained through cDNA synthesis, inverse PCR, and sequencing. A single-chain variable fragment (scFv) with an N-terminal Cys-tag was expressed in E. coli Shuffle T7, resulting in a final yield of 9.8 mg L-1. The fluorescent dye was labeled on the Cys-tag of the anti-P-III-NP scFv using maleimide-thiol click chemistry, and the spacer arm lengths between the maleimide-fluorescent dyes were compared. Consequently, a TAMRA-C6-labeled quenchbody exhibited antigen-dependent fluorescence signals and demonstrated its ability to detect P-III-NP at concentrations as low as 0.46 ng mL-1 for buffer samples, 1.0 ng mL-1 for 2 % human serum samples. SIGNIFICANCE: This one-step P-III-NP detection method provides both qualitative and quantitative outcomes within a concise 5-min timeframe. Furthermore, its application can be expanded using a 96-well platform and human serum, making it a high-throughput and sensitive method for testing fibrotic biomarkers.

Fouling-Free electrochemical strategy based on vertically-aligned peptide layer for cardiac troponin I sensitive detection in human serum.

BACKGROUND: Cardiac troponin I (CTnI) is demonstrated as one of the most promising disease biomarkers for early diagnosing acute myocardial infarction (AMI). To date, electrochemical immunosensors have been extensively studied in the field of cTnI determination. But highly accurate and sensitive cTnI detection by this method is still a challenge due to non-specific adsorption on electrode interfaces in complex human serum. As a result, it is necessary to develop an antifouling electrochemical immunosensor with high sensitivity for the detection of cTnI. RESULTS: In this work, an antifouling electrochemical immunosensor was constructed based on vertically-aligned peptide layer consisting of Au nanoparticles (AuNPs) and amphiphilic CEAK16 peptide (CEAK16@AuNPs) for sensitive and accurate detection of cTnI in human serum. The vertically-aligned CEAK16@AuNPs interface provided a stable hydration layer originated from attraction of water molecules by amino acids on the hydrophilic side of the CEAK16, which effectively reduced non-specific adsorption and enhanced electron transfer rate. The cTnI immunosensor possessed great analytical performance with a wide range from 1 fg mL-1 to 1 µg mL-1 and a low detection limit of 0.28 fg mL-1 (S/N = 3). Additionally, the proposed CEAK16@AuNPs sensing interface showed excellent long-term antifouling performance and electrochemical activity that preserved 80 % of the initial signal after 20-days exposure in human serum samples. Consequently, the cTnI immunosensor displayed excellent detection accuracy compared to clinical methods and owned good selectivity, stability and reproducibility. SIGNIFICANCE: The development of this strategy provides a versatile tool for accurate quantitative cTnI analysis in real human serum, thus helping to achieve early AMI diagnosis effectively and holding the promising potentials for other immunosensor in disease diagnosis.

An electrochemical/SERS dual-mode immunosensor using TMB/Au nanotag and Au@2D-MoS2 modified screen-printed electrode for sensitive detection of prostate cancer biomarker.

This study describes a novel dual-mode immunosensor that combines electrochemical (EC) and surface-enhanced Raman scattering (SERS) techniques for the detection of prostate-specific antigen (PSA), a biomarker associated with prostate cancer. The sensor consists of a nanocomposite of gold nanoparticles (AuNPs) deposited on two-dimensional (2D) molybdenum disulfide (Au@MoS2) modified on a working carbon electrode of a screen-printed electrode (SPE). Subsequently, the primary antibody (Ab1) is immobilized on the modified electrode, creating Ab1/Au@MoS2/SPE for specific recognition of the target PSA. In parallel, AuNPs are conjugated with a secondary antibody (Ab2) and a probe molecule, 3,3',5,5'-tetramethylbenzidine (TMB), leading nanotags (TMB/Ab2/AuNPs) formation exhibiting strong SERS and EC responses. Upon the presence of the target, sandwich immunocomplexes can be formed through antigen-antibody interactions (Ab1-PSA-Ab2). The differential pulse voltammetry (DPV) technique is employed for EC detection mode, while a handheld Raman spectrometer with a 785 nm excitation laser is utilized to collect SERS signals. The developed system demonstrates excellent selectivity and sensitivity, with low limits of detection (LODs) of 3.58 pg mL-1 and 4.83 pg mL-1 for EC and SERS sensing, respectively. Importantly, the dual-mode immunosensor proves effective quantifying PSA protein in human serum samples with good recovery. Given its high sensitivity and proficiency in analyzing biological samples, this proposed immunosensor holds promise as an alternative tool for the early diagnosis of cancers.