Simultaneous immunodetection of multiple cervical cancer biomarkers based on a signal-amplifying redox probes/polyethyleneimine-coated gold nanoparticles/2D tungsten disulfide/graphene oxide nanocomposite platform.

To advance cervical cancer diagnostics, we propose a state-of-the-art label-free electrochemical immunosensor designed for the simultaneous detection of multiple biomarker proteins (p16INK4a, p53, and Ki67). This immunosensor is constructed using a polyethyleneimine-coated gold nanoparticles/2D tungsten disulfide/graphene oxide (PEI-AuNPs/2D WS2/GO) composite-modified three-screen-printed carbon electrode (3SPCE) array. The 2D WS2/GO hybrid provides a large specific surface area for supporting well-dispersed PEI-AuNPs and adsorbed redox-active species, enhancing overall performance. The PEI-AuNPs-decorated 2D WS2/GO composite not only improves electrode conductivity but also increases the antibody loading capacity. Redox-active species, including Cd2+ ions, 2,3-diaminophenazine (DAP), and methylene blue (MB), serve as distinct signaling compounds to quantitatively detect the cervical cancer biomarkers p16INK4a, p53, and Ki67, respectively. Additionally, the immunosensor demonstrates the detection with high sensitivity, good storage stability, high selectivity, and acceptable reproducibility. This immunosensor demonstrates a good linear relationship with the logarithm of protein concentrations. Additionally, the immunosensor also demonstrates high sensitivity, good storage stability, high selectivity, and acceptable reproducibility. Our promising results and the successful application of the immunosensor in detecting three tumor markers in human serum highlight its potential for clinical diagnosis of cervical cancer.

Au NPs modified Ni-B nanosheets/graphene oxide three-dimensional network as label-free electrochemical immunosensor for the detection of diethylstilbestrol.

Three-dimensional (3D) network provide a promising platform for construction of high sensitive electrochemical immunosensor due to the benefits of high specific surface area and electron mobility. Herein, a sensitive label-free electrochemical immunosensor based on Au nanoparticles modified Ni-B nanosheets/graphene matrix was constructed to detect diethylstilbestrol (DES). The 3D network not only could increase the electron transport rate and surface area, but also could provide confinement area, which is conducive to increases the collision frequency with the active site. Moreover, Au NPs also have good biocompatibility, which is beneficial for ligating antibodies. Benefiting from the 3D network structure and Au collective effect, the electrochemical immunosensor possess sterling detection ability with wide linear response range (0.00038-150 ng/mL) and low detection limit (31.62 fg/mL). Moreover, the constructed immunosensor can also be extend to detect DES in Tap-water and river water. This work may provide a novel material model for the construction of high sensitive immunosensor.

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.

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.

Enzymatic Precipitation of Highly Electroactive and Ion-Transporting Prussian Blue for a Sensitive Electrochemical Immunosensor.

Sensitive and/or multiplex electrochemical biosensors often require efficient (bio)catalytic conversion of substrates into insoluble electroactive products. The enzymatic formation and precipitation of coordination polymers under mild conditions offers a promising solution for this purpose. Herein, we report the enzymatic precipitation of Prussian blue (PB), a highly electroactive and ion-transporting coordination polymer, on an immunosensing electrode for application in a sensitive electrochemical immunosensor for detecting thyroid-stimulating hormone (TSH). Five pairs of redox enzymes and their specific reductants were examined to achieve rapid PB precipitation and electrochemical oxidation. Among these pairs, O2-insensitive flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) paired with glucose yielded the highest electrochemical signal-to-background (S/B) ratio. FAD-GDH catalyzed the conversion of Fe(CN)63- to Fe(CN)64-, which coordinated with Fe3+, leading to PB formation and subsequent precipitation through repeated conversions. The resulting PB precipitate, with its close proximity to the electrode, facilitated rapid electrochemical oxidation and generated a strong electrochemical signal. Notably, the precipitation and electrochemical oxidation of PB were more effective than those of its analogues. When applied to a sandwich-type immunosensor for TSH detection, the enzymatic PB precipitation achieved a calculated detection limit of approximately 2 pg/mL in artificial serum, covering the clinically relevant range. These findings indicate the potential widespread utility of PB precipitation and electrochemical oxidation for sensitive multiplex biomarker detection.

Cubic Na0.5Bi0.5TiO3 nanoperovskite significantly expands the application of sensitive immunosensor for the detection of carcinoembryonic antigen.

Nanosized sodium bismuth perovskite titanate (NBT) was synthesized and first used as the electrochemical immune sensing platform for the sensitive detection of carcinoembryonic antigen (CEA). Gold nanoparticles (Au NPs) grew on the surface of NBT through forming Au-N bond to obtain Au@NBT, and a label-free electrochemical immunosensor was proposed using Au@NBT as an immunosensing recognizer towards CEA. The well-ordered crystal structure of NBT was not changed at all after the modification of Au NPs outside, but significantly improved the conductivity, catalytic activity, and biocompatibility of the Au@NBT-modified electrode. The unique cubic crystal nanostructure of NBT offered a large active area for both Au NP modification and the subsequent immobilization of biomolecules over the electrode surface, triggering the effective generation of promising properties of the proposed Au@NBT-based electrochemical immunosensor. As expected, favorable detection performances were achieved using this immunosensor towards CEA detection, where a good linear relationship between the current response and CEA concentration was obtained in the concentration range 10 fg mL-1 to 100 ng mL-1 with a low detection limit (LOD) of 13.17 fg mL-1. Also, the significantly enhanced selectivity, and stability guaranteed the promising electrochemical properties of this immunosensor. Furthermore, the analysis of real serum samples verified the high feasibility of this new method in clinical CEA detection. This work opens a new window for the application of nanoperovskite in the early detection of CEA.

A plug-and-play, easy-to-manufacture fluidic accessory to significantly enhance the sensitivity of electrochemical immunoassays.

Earlier access to patients' biomarker status could transform disease management. However, gold-standard techniques such as enzyme-linked immunosorbent assays (ELISAs) are typically not deployed at the point-of-care due to their cumbersome instrumentation and complexity. Electrochemical immunosensors can be disruptive in this sector with their small size and lower cost but, without further modifications, the performance of these sensors in complex media (e.g., blood) has been limited. This paper presents a low-cost fluidic accessory fabricated using widely accessible materials and processes for boosting sensor sensitivity through confinement of the detection media next to the electrode surface. Liquid confinement first highlighted a spontaneous reaction between the pseudoreference electrode and ELISA detection substrate 3,3',5,5'-tetramethylbenzidine (TMB) that decreases the amount of oxTMB available for detection. Different strategies are investigated to limit this and maximize reliability. Next, flow cell integration during the signal amplification step of sensor preparation was shown to substantially enhance the detection of cytokine interleukin-6 (IL-6) with the best sensitivity boost recorded for fresh human plasma (x7 increase compared to x5.8 in purified serum and x5.5 in PBS). The flow cell requires no specialized equipment and can be seamlessly integrated with commercial sensors, making an ideal companion for electrochemical signal enhancement.

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.

AuPt/NF prepared with the lattice induction of substrate was applied to construct the electrochemical immunosensor for PCT detection.

For the electrodeposition, the conductivity and lattice structure of substrate is important to the morphology and lattice of the deposited material. In this study, gold-platinum (AuPt) nanopartical was deposited on nickel foam (NF) based on the lattice induced orientation of the Ni substrate, and the obtained AuPt/NF was applied to construct electrochemical impedimetric immunosensor for procalcitonin (PCT) detection. As a new immunosensor matrix, NF with higher electrical conductance, flexibility and specific surface area, which can improve the plasticity, sensitivity and universality of the immunoelectrode. Due to the lattice matching between Au and Ni, ultrathin AuPt nanolayer with good biocompatibility and large surface area can be modified on the NF surface, which can bind more biomolecules and amplifies the change of impedance signal. Based on the synergistic effect between AuPt and NF, PCT detection based on this electrochemical impedimetric immunosensor with a wide linear range (0.2 pg mL-1 to 20 ng mL-1) and low detection limit (0.11 pg mL-1). In addition, this impedimetric immunosensor exhibits high recovery in the PCT detection of serum samples. This work provides a new thought and method for the construction of electrochemical immunosensor.

An ultrasensitive sandwich-type electrochemical immunosensor based on rGO-TEPA/ZIF67@ZIF8/Au and AuPdRu for the detection of tumor markers CA72-4.

Cancer antigen 72-4 (CA72-4) is an important marker of cancer detection, and accurate detection of CA72-4 is urgently required. Herein, a sandwich-type immunosensor was constructed for detection CA72-4 based on composite nanomaterial as the substrate material and trimetal nanoparticles as the nanoprobe. The composite nanomaterial rGO-TEPA/ZIF67@ZIF8/Au used as a selective bio-recognition element were modified on the glassy carbon electrode (GCE) surface. Meanwhile, the electrochemical nanoprobes were fabricated through the AuPdRu trimeric metal. After the target antigen 72-4 were captured, the nanoprobes were further assembled to form an antibody1 (Ab1)- antigen-antibody2 (Ab2) nanoprobes sandwich-like system on the electrode surface. Then, hybrid the substrate material rGO-TEPA/ZIF67@ZIF8/Au and the AuPdRu trimeric metal nanoprobes efficiently catalyzed the reduction of H2O2 and amplified the electrochemical signals. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and Chronoamperometry (I-T) methods were used to characterize the performance and detection capabilities for CA72-4 of the prepared immunosensors. The results showed that the detection limit was 1.8 × 10-5 U/mL (S/N = 3), and the linear range was 0.001-1000 U/mL. This study provides a new signal amplification strategy for electrochemical sensors and a theoretical basis for the clinical application of immunosensor to detect other tumor markers.

Construction and evaluation of AuNPs enhanced electrochemical immunosensors with [Fe(CN)6]3-/4- and PPy probe for highly sensitive detection of human chorionic gonadotropin.

Human chorionic gonadotropin (HCG), a vital protein for pregnancy determination and a marker for trophoblastic diseases, finds application in monitoring early pregnancy and ectopic pregnancy. This study presents an innovative approach employing electrochemical immunosensors for enhanced HCG detection, utilizing Anti-HCG antibodies and gold nanoparticles (AuNPs) in the sensor platform. Two sensor configurations were optimized: BSA/Anti-HCG/c-AuNPs/MEL/e-AuNPs/SPCE with [Fe(CN)6]3-/4- as a redox probe (1) and BSA/Anti-HCG/PPy/e-AuNPs/SPCE using polypyrrole (PPy) as a redox probe (2). The first sensor offers linear correlation in the 0.10-500.00 pg∙mL-1 HCG range, with a limit of detection (LOD) of 0.06 pg∙mL-1, sensitivity of 32.25 µA∙pg-1∙mL∙cm-2, RSD <2.47 %, and a recovery rate of 101.03-104.81 %. The second sensor widens the HCG detection range (40.00 fg∙mL-1-5.00 pg∙mL-1) with a LOD of 16.53 fg∙mL-1, ensuring precision (RSD <1.04 %) and a recovery range of 94.61-106.07 % in serum samples. These electrochemical immunosensors have transformative potential in biomarker detection, offering enhanced sensitivity, selectivity, and stability for advanced healthcare diagnostics.

Development of quantitative detection methods for four Alzheimer's disease specific biomarker panels using electrochemical immunosensors based on enzyme immunoassay.

Accurate and timely diagnosis of Alzheimer's disease (AD) is necessary to maximize the effectiveness of treatment and using biomarkers for diagnosis is attracting attention as a minimally invasive method with few side effects. Electrochemical immunosensor (EI) is a method that is in the spotlight in the medical and bioanalytical fields due to its portability and field usability. Here, we quantified four AD specific biomarkers using EIs based on enzyme immunoassay. We selected and developed quantitative methods for the biomarkers using screen-printed gold electrodes. For three biomarkers, quantification was performed using competition immunoassays in which antigen-antibody premix mixtures were applied to antigen-immobilized electrodes and the limit of detection (LOD) values were secured, 1.20 ng/ml, 1.30 ng/ml, and 1.74 ng/ml, respectively. For the other, a sandwich immunoassay using antibody pair was selected for quantification and LOD was also achieved as 0.077 ng/ml. All four biomarkers in buffer samples were successfully quantified and reliable R2 values were obtained, and reliable calibration curves were secured for three biomarkers in spiked human serum samples. The immunosensors developed and will be optimized are expected to be used in various fields, including detection of biomarkers for not only AD but also related diseases.

An electrochemical immunosensor based on MXene-GQD/AuNPs for the detection of trace amounts of CA-125 as specific tracer of ovarian cancer.

An electrochemical immunoassay system was developed to detect CA-125 using a glassy carbon electrode (GCE) modified with MXene, graphene quantum dots (GQDs), and gold nanoparticles (AuNPs). The combined MXene-GQD/AuNPs modification displayed advantageous electrochemical properties due to the synergistic effects of MXene, GQDs, and AuNPs. The MXene-GQD composite in the modified layer provided strong mechanical properties and a large specific surface area. Furthermore, the presence of AuNPs significantly improved conductivity and facilitated the binding of anti-CA-125 on the modified GCE, thereby enhancing sensitivity. Various analytical techniques such as FE-SEM and EDS were utilized to investigate the structural and morphological characteristics as well as the elemental composition. The performance of the developed immunosensor was assessed using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), square wave voltammetry (SWV), and differential pulse voltammetry (DPV). Under optimized conditions in a working potential range of -0.2 to 0.6 V (vs. Ag/AgCl), the sensitivity, linear range (LR), limit of detection (LOD), and correlation coefficient (R2) were determined to be 315.250 µA pU.mL-1/cm2, 0.1 to 1 nU/mL, 0.075 nU/mL, and 0.9855, respectively. The detection of CA-125 in real samples was investigated using the developed immunoassay platform, demonstrating satisfactory results including excellent selectivity and reproducibility.

Electrochemical Detection of a Breast Cancer Biomarker with an Amine-Functionalized Nanocomposite Pt-Fe3O4-MWCNTs-NH2 as a Signal-Amplifying Label.

We report an ultrasensitive sandwich-type electrochemical immunosensor to detect the breast cancer biomarker CA 15-3. Amine-functionalized composite of reduced graphene oxide and Fe3O4 nanoparticles (MRGO-NH2) was used as an electrochemical sensing platform material to modify the electrodes. The nanocomposite comprising Pt and Fe3O4 nanoparticles (NPs) anchored on multiwalled carbon nanotubes (Pt-Fe3O4-MWCNTs-NH2) was utilized as a pseudoenzymatic signal-amplifying label. Compared to reduced graphene oxide, the composite MRGO-NH2 platform material demonstrated a higher electrochemical signal. In the Pt-Fe3O4-MWCNTs-NH2 label, multiwalled carbon nanotubes provided the substratum to anchor abundant catalytic Pt and Fe3O4 NPs. The nanocomposites were thoroughly characterized using transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. An electroanalytical study and prevalidation of the immunosensor was carried out. The immunosensor exhibited exceptional capabilities in detecting CA 15-3, offering a wider linear range of 0.0005-100 U mL-1 and a lower detection limit of 0.00008 U mL-1. Moreover, the designed immunosensor showed good specificity, reproducibility, and acceptable stability. The sensor was successfully applied to analyze samples from breast cancer patients, yielding reliable results.

A dual-mode label-free electrochemical immunosensor for ultrasensitive detection of procalcitonin by on-site vulcanization of dual-MOF heterostructure.

Detection of procalcitonin (PCT) is crucial for the early identification of sepsis. PCT is primarily utilized in the multiple diagnosis of bacterial and viral illnesses along with to guide the application of antibiotics. Considering their advantages of high specificity and straightforward usage, electrochemical immunosensors offer significant application prospects in the detection of disease indicators. A dual-mode electrochemical immunosensor was constructed in this study to reliably identify PCT. In light of the synergistic effect of the dual-MOF derived heterostructure, the immunosensor demonstrating excellent square wave voltammetry (SWV) signals as well as significant catalytic activity for the H2O2 redox process. In addition to maintaining a low detection limit (SWV: 0.31 fg/mL and i-t: 0.098 fg/mL), the immunosensor offers an extensive linear response range (0.000001-100 ng/mL). The excellent performance is on account of the introduction of the local on-site sulfurized dual-MOF heterostructure with abundant metal chalcogenides/MOF interfaces, which boosts the specific surface area, offers an abundance of active sites, enhances conductivity, and raises catalytic activity. Furthermore, the immunosensor exhibits outstanding specificity, stability and reproducibility for the determination of PCT in serum, which is of great crucial for the clinical screening and diagnosis of sepsis.

Disposable graphene-oxide screen-printed electrode integrated with portable device for detection of SARS-CoV-2 in clinical samples.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnosis is the need of the hour, as cases are persistently increasing, and new variants are constantly emerging. The ever-changing nature of the virus leading to multiple variants, has brought an imminent need for early, accurate and rapid detection methods. Herein, we have reported the design and fabrication of Screen-Printed Electrodes (SPEs) with graphene oxide (GO) as working electrode and modified with specific antibodies for SARS-CoV-2 Receptor Binding Domain (RBD). Flexibility of design, and portable nature has made SPEs the superior choice for electrochemical analysis. The developed immunosensor can detect RBD as low as 0.83 fM with long-term storage capacity. The fabricated SPEs immunosensor was tested using a miniaturized portable device and potentiostat on 100 patient nasopharyngeal samples and corroborated with RT-PCR data, displayed 94 % sensitivity. Additionally, the in-house developed polyclonal antibodies detected RBD antigen of the mutated Omicron variant of SARS-CoV-2 successfully. We have not observed any cross-reactivity/binding of the fabricated immunosensor with MERS (cross-reactive antigen) and Influenza A H1N1 (antigen sharing common symptoms). Hence, the developed SPEs sensor may be applied for bedside point-of-care diagnosis of SARS-CoV-2 using miniaturized portable device, in clinical samples.

Gold nanostructure-enhanced immunosensing: ultra-sensitive detection of VEGF tumor marker for early disease diagnosis.

We present an advanced electrochemical immunosensor designed to detect the vascular endothelial growth factor (VEGF) precisely. The sensor is constructed on a modified porous gold electrode through a fabrication process involving the deposition of silver and gold on an FTO substrate. Employing thermal annealing and a de-alloying process, the silver is eliminated from the electrode, producing a reproducible porous gold substrate. Utilizing a well-defined protocol, we immobilize the heavy-chain (VHH) antibody against VEGF on the gold substrate, facilitating VEGF detection through various electrochemical methods. Remarkably, this immunosensor performs well, featuring an impressive detection limit of 0.05 pg/mL and an extensive linear range from 0.1 pg/mL to 0.1 µg/mL. This emphasizes it's to measure biomarkers across a wide concentration spectrum precisely. The robust fabrication methodology in this research underscores its potential for widespread application, offering enhanced precision, reproducibility, and remarkable detection capabilities for the developed immunosensor.

Expression of scFv-anti-CHIKV-E2 in Escherichia coli with chaperones Co-expression, and its functional assay by electrochemical immunosensor.

Single Chain Variable Fragment (scFv), a small fragment of antibody can be used to substitute the monoclonal antibody for diagnostic purposes. Production of scFv in Escherichia coli host has been a challenge due to the potential miss-folding and formation of inclusion bodies. This study aimed to express anti-CHIKV E2 scFv which previously designed specifically for Asian strains by co-expression of three chaperones that play a role in increasing protein solubility; GroEL, GroES, and Trigger Factor. The scFv and chaperones were expressed in Origami B E. coli host under the control of the T7 promoter, and purified using a Ni-NTA column. Functional assay of anti-CHIKV-E2 scFv was examined by electrochemical immunosensor using gold modified Screen Printed Carbon Electrode (SPCE), and characterized by differential pulses voltammetry (DPV) using K3[Fe(CN)6] redox system and scanning microscope electron (SEM). The experimental condition was optimized using the Box-Behnken design. The results showed that co-expression of chaperone increased the soluble scFv yield from 54.405 µg/mL to 220.097 µg/mL (~5×). Furthermore, scFv can be used to detect CHIKV-E2 in immunosensor electrochemistry with a detection limit of 0.74048 ng/mL and a quantification limit of 2,24388 ng/mL. Thus, the scFv-anti-CHIKV-E2 can be applied as a bioreceptor in another immunoassay method.

A sensitive electrochemical immunosensor based on high-efficiency catalytic cycle amplification strategy for detection of cardiac troponin I.

An electrochemical immunosensor based on the novel high efficiency catalytic cycle amplification strategy for the sensitive detection of cardiac troponin I (cTnI). With its variable valence metal elements and spiny yolk structure, the Cu2O/CuO@CeO2 nanohybrid exhibits high speed charge mobility and exceptional electrochemical performance. Notably, fluorite-like cubic crystal CeO2 shell would undergo redox reaction with Cu2O core, which successfully ensures the continuous recycling occurrence of "fresh" Cu (II)/Cu (I) and Ce (Ⅳ)/Ce (Ⅲ) pairs at the electrode interface. The "fresh" active sites continue to emerge constantly, resulting in a significant increase in the current signal. In light of the electrochemical characterization, the electron transfer pathway and catalytic cycle mechanism among CeO2, Cu2O and CuO were further discussed. The developed electrochemical immunosensor detected cTnI from 100 fg/mL to 100 ng/mL with a LOD of 15.85 fg/mL under optimal conditions. The analysis results indicate that the immunosensor would hold promise for broad application prospects in the biological detection for other biomarkers.

Point-of-Care Electrochemical Immunosensor Applied against Nosocomial Infection: Staphylococcus aureus Detection in Human Hand Skin.

Staphylococcus aureus is an important pathogen that causes nosocomial infections, resulting in unacceptable morbidity and mortality rates. In this work, we proposed the construction of a nanostructured ZnO-based electrochemical immunosensor for qualitative and semiquantitative detection of S. aureus using simple methods for growing zinc oxide nanorods (ZnO NRs) on a sensor board and immobilizing the anti-S. aureus antibody on ZnO NRs through cystamine and glutaraldehyde. The immunosensor detected S. aureus in the 103-107 colony-forming unit (CFU) mL-1 range and showed a limit of detection (LoD) around 0.792 × 103 CFU mL-1. Beyond a satisfactory LoD, the developed immunosensor presented other advantages, such as high versatility for point-of-care assays and a suitable selective factor that admits the detection of the S. aureus concentration range in human hand skin after washing. Moreover, the immunosensor showed the potential to be an excellent device to control nosocomial infection by detecting the presence of S. aureus in human hand skin.