Immunosensing Platform Research Articles

Biofunctionalized carbonaceous nanoflakes based efficient electrochemical biosensor for SAA biomarker detection

Swine flu is one of the major causes of death worldwide in both humans as well as in animals. In the biological sample of swine flu patients, there are several biomarkers secreted in which Serum Amyloid A (SAA) is one of the promising biomarker. Based on the concentration of SAA apolipoprotein, swine flu patients can be easily differentiated from the normal subject. Keeping these in view, we report the results of the studies related to the fabrication of an immunosensing platform for SAA apolipoprotein biomarker detection. For the fabrication of the immunosensing platform, we used ultrathin carbonaceous nanoflakes [Graphitic carbon nitride nanoflakes (g-C3N4NFs)] as transducer material. The g-C3N4NFs were prepared by polycondensation of melamine followed by liquid stripping, further treated with 3-(aminopropyl) triethoxysilane (APTES) to introduce amino group moiety. The APTES functionalized g-C3N4NFs were deposited onto ITO coated glass electrode using an electrophoretic deposition technique by providing an optimized DC potential of 30 V for 120 s. Further, biofunctionalization was done by immobilizing the specific anti-SAA monoclonal antibody onto APTES/g-C3N4NFs/ITO electrode via EDC-NHS chemistry and non-specific area were blocked with BSA molecules. Several non-distracting techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Fourier-transform infrared spectroscopy were used for the structural, morphological, and chemical characterization of synthesized nanomaterials as well as fabricated electrodes. Moreover, cyclic voltammetry techniques were used for electrochemical characterizations as well as response studies. The fabricated immunosensing platform i.e., BSA/anti-SAA/APTES/g-C3N4NFs/ITO is capable to detect SAA protein with linear detection range of 10–100 μg mL−1, limit of detection of 6.17 μg mL−1 and sensitivity of 2.42 μA mL μg−1cm−2.

Lab-on-PCB-Based Electrical Immunosensing Platform for Point-of-Care Detection of SARS-CoV-2

The present work shows a multiplexed lab-on-printed circuit board (PCB) platform for label-free immunosensing of SARS-CoV-2 nucleocapsid and spike antigens based on electrical impedance measurements. The sensor consists of an interdigitated electrode of soft gold integrated on a PCB with microwells for sample loading. A mercaptoundecanoic acid–protein-G-based site-specific biofunctionalization strategy is employed to efficiently immobilize dual antibodies on the device surface toward the sensitive and rapid antigen test of SARS-CoV-2. Electrical impedance measurements carried out in a point-of-care setting using the PalmSens Sensit Smart system that could detect nucleocapsid and spike proteins with a detection limit of 40 and 20 pg each. Experiments with nasopharyngeal swab samples from <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> = 5 healthy and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> = 14 SARS-CoV-2 positive subjects showed significantly different electrical responses for subjects with high viral load ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ct</i> < 25) compared with healthy subjects and control.

An electrochemical immunosensor for an alpha-fetoprotein cancer biomarker on a carbon black/palladium hybrid nanoparticles platform.

The early detection of cancer is a key step in cancer survival. Thus, there is a need to develop low-cost technologies, such as electrochemical immunosensor technologies, for timely screening and diagnostics. The discovery of alpha-feto protein (AFP) as a tumour-associated antigen lends AFP as a biomarker for cancer detection and monitoring. Thus, immunosensors can be developed to target AFP in cancer diagnostics. Hence, we report the application of a hybrid nanocomposite of carbon black nanoparticles (CBNPs) and palladium nanoparticles (PdNPs) as a platform for the electrochemical immunosensing of cancer biomarkers. The hybrid carbon-metal nanomaterials were immobilised by using the drop-drying and electrodeposition technique on a glassy carbon electrode, followed by the immobilisation of the anti-AFP to fabricate an immunosensor. The nanoparticles were characterised with electron microscopy, voltammetry, and electrochemical impedance spectroscopy (EIS). Square wave voltammetry (SWV) and EIS were used to study the immunosensor signal toward the bio-recognition of the AFP cancer biomarker. The hybrid nanoparticles enhanced the immunosensor performance. A linear detection range from 0.005 to 1000 ng mL-1 with low detection limits of 0.0039 ng mL-1 and 0.0131 ng mL-1 were calculated for SWV and EIS, respectively. The immunosensor demonstrated good stability, reproducibility, and selectivity. Its real-life application potential was tested with detection in human serum matrix.

Detection of specific antibodies against SARS-CoV-2 spike protein via ultra-sensitive bio-functionalized carbonnitride-reduced graphene oxide electrochemical immunosensing platform in real samples

Ultrasensitive immunosensing device based on bio-functionalized C3N4/RGO nanocomposite allows for exact differentiation between positive and negative real COVID-19 patient samples.

Integrating a zwitterionic peptide with a two-photoelectrode system for an advanced photoelectrochemical immunosensing platform.

An ingenious strategy with the integration of a zwitterionic peptide into a two-photoelectrode system was reported to construct an advanced photoelectrochemical immunosensing platform. The strategy has endowed the platform with both excellent photoelectric properties and an antifouling ability, and was capable of accurate and sensitive detection of target biomarkers in biological specimens.

Platinum nanozyme-mediated temperature sensor for sensitive photothermal immunoassay of YKL-40 under near-infrared light

This work reports a photothermal immunoassay for the sensitive screening of YKL-40 coupling near-infrared light-excited platinum nanoparticles with a handheld digital thermometer.

β-Cyclodextrin-functionalized Ti3C2Tx MXene nanohybrids as innovative signal amplifiers for the electrochemical sandwich-like immunosensing of squamous cell carcinoma antigen.

Herein, a simple and highly sensitive electrochemical sandwich-like immunosensor for the squamous cell carcinoma antigen (SCCA) was constructed using gold nanoparticle/graphene nanosheet (Au/GN) nanohybrids as a sensing platform and β-cyclodextrin/Ti3C2Tx MXenes (β-CD/Ti3C2Tx) as a signal amplifier. The good biocompatibility and large surface area as well as the high conductivity of Au/GN allow the platform to load primary antibodies (Ab1) and facilitate electron transport. In the case of the β-CD/Ti3C2Tx nanohybrids, the β-CD molecule is dedicated to binding secondary antibodies (Ab2) through host-guest interactions, thus inducing the formation of the sandwich-like structure Ab2-β-CD/Ti3C2Tx/SCCA/Ab1/Au/GN in the presence of SCCA. Interestingly, Cu2+ can be adsorbed and self-reduced on the surface of the sandwich-like structure to form Cu0 since Ti3C2Tx MXenes can exhibit superior adsorption and reduction capabilities towards Cu2+, and a prominent current signal of Cu0 can be observed via differential pulse voltammetry. Based on this principle, an innovative signal amplification strategy has been proposed for SCCA detection, which avoids the process of labeling the probe and the specific immobilization step of catalytic components on the surface of amplification markers. After the optimization of various conditions, a wide linear range from 0.05 pg mL-1 to 20.0 ng mL-1, coupled with a low detection limit of 0.01 pg mL-1, was obtained for SCCA analysis. The proposed method for SCCA detection was also applied in real human serum samples and the observed results are satisfactory. This work opens up new pathways for constructing electrochemical sandwich-like immunosensors for SCCA and other targets.

Two-phase dual-signal-readout immunosensing platform based on multifunctional carbon nano-onions for ovarian cancer biomarker detection.

In order to detect early tumor markers and gain valuable time for treatment, there is an urgent need to develop a fast, cheap, and ultrasensitive multi-reading sensing platform. Herein, a solid/liquid two-phase dual-output biosensor was explored based on a sensitized sonochemiluminescence (SCL) strategy and a multifunctional carbon nano-onion (CNO) probe. It is clear that ultrasonic radiation caused the formation of hydroxyl radicals (˙OH), triggering the SCL signal of the emitter lucigenin (Luc2+). Meanwhile, titanium carbide nanodots and ethanol were used to enhance the SCL signal, and an astonishingly linear enhancement of the SCL intensity was produced with increasing ethanol concentration. More importantly, the CNOs, with their excellent photothermal properties and adsorption capacity, can output both the temperature signal and an enhanced SCL strength from the solid-liquid phase. Through inter-calibration of the signals from the two-phases, this biosensor shows excellent analytical performance for the detection of the ovarian cancer biomarker, human epididymis-specific protein 4, from 10-5 to 10 ng mL-1 with a low detection limit of 3.3 fg mL-1. This work not only provides a novel two-phase signal-output mode that broadens the scope of multiperformance joint applications of CNOs, but also enriches the quantitative detection of point-of-care testing.

Photoelectrochemical immunoassay for thyroglobulin on nanogold-functionalized BiVO4 photoanode coupling with enzymatic biocatalytic precipitation

Methods derived from photoelectrochemical (PEC) have been constructed for immunoassays, but most involve the split-type immunoreaction modes, and thus easily cause unpredictable intermediate precision. Herein, we innovatively designed an integrated PEC immunosensing platform for the quantitative monitoring of thyroglobulin (TG) on the gold nanoparticles (AuNPs)-functionalized BiVO4 photoanode coupling with enzymatic biocatalytic precipitation (EBCP). This sensing system could simultaneously implement the immunoreaction and photocurrent measurement. Anti-TG capture antibodies were modified onto AuNPs-decorated BiVO4 photoelectrode. A sandwich-type immunoreaction was carried out in the presence of target TG using horseradish peroxidase (HRP)-conjugated anti-TG detection antibody. The carried HRP molecules catalyzed 4-chloro-1-naphthol (4-CN) to generate an insoluble benzo-4-chlorohexadienone product on the photoanode in the presence of peroxide hydrogen, thereby decreasing the photocurrent. Under optimal conditions, the PEC immunosensors gave good photocurrent responses toward target TG within the dynamic range of 0.01–10 ng mL−1 at a detection limit of 7.6 pg mL−1. Good repeatability and precision, high specificity and acceptable storage stability were acquired during the measurement. No significant differences were encountered for screening 15 human serum specimens between the developed PEC immunoassay and commercially available enzyme-linked immunosorbent assay (ELISA) method for the detection of target TG. Significantly, PEC immunosensing system offers promise for simple and cost-effective analysis of disease-related biomarkers.

A photoelectrochemical immunosensing platform for ultrasensitive detection of alpha-fetoprotein based on a signal amplification strategy

For the first time, a PEC immunosensor based on a signal amplification strategy is successfully constructed to quantitatively detect alpha-fetoprotein in serum sample. Three favorable factors explain the ultra-high sensitivity of this method. Firstly, compared with pure BiPO4, the BiPO4/BiOBr heterojunction has a narrower band gap, which expands the light absorption range and enables the light energy to be fully utilized. Secondly, the separation of photogenerated electrons and hole pairs during PEC detection is due to the efficient matching of energy levels among BiPO4, BiOBr and CdS, inhibiting the recombination of photogenerated electrons, which improves the performance of PEC immunosensor. Thirdly, due to the presence of CdS, the light absorption capability of the sensor is enhanced, more electron-hole pairs are generated, and the photocurrent signal is increase. Under the optimal conditions, the PEC immunosensor shows a wide linear range of 0.001–1000 ng/mL for AFP and a low detection limit of 0.82 pg/mL. The PEC immunosensor developed in this experiment has excellent reproducibility, stability and high sensitivity, and also achieves satisfactory results in the analysis of human serum samples, establishing a new analytical method for biomarker detection.

An ultrasensitive probe-free electrochemical immunosensor for gibberellins employing polydopamine-antibody nanoparticles modified electrode

Gibberellins (GA3) is an ubiquitous plant hormone, which plays a regulatory role in different growth stages of plants, so it is of great significance to develop a sensitive quantitative analysis method for GA3. In this study, carboxylated graphene oxide- carboxylated multi-walled carbon nanotubes-Fc (GO-MWNT-Fc) composite material and PDANPs-antibody (PDANPs-Ab) were sequentially modified to screen-printed electrodes (SPEs), and an ultrasensitive probe-free immunosensor for GA3 was developed. Fc was applied to generate electrochemical signals. GO-COOH and MWNT-COOH can increase the catalytic ability of the sensor and bind the PDANPs-Ab nanoparticles. PDANPs nanomaterial were synthetized by a facile self-polymerization and used to bind with antibody, so as to increase the antibody loading of the sensor. The as-prepared immunosensor has the widest detection range (100 aM-1 mM) and lowest detection limit (17.4 aM) for GA3 up to date. To our knowledge, it is the first electrochemical immunosensor for GA3. By changing the GA3 antibody to ABA antibody, a sensitive and selective immunosensor for ABA was also fabricated. This immunosensor platform is simple, sensitive, and low cost. It opens broad prospect in on-site applications for biosensors in detecting of various biomolecules in precision agriculture.

Simple and Sensitive Electrochemical Sandwich-type Immunosensing of Human Chorionic Gonadotropin based on b-cyclodextrin Functionalized Graphene

The effective detection of human chorionic gonadotropin (HCG) is considerably important for the clinical diagnosis of both of early pregnancy and nonpregnancy-related diseases. In this work, a simple and sensitive electrochemical sandwich-type immunosensing platform was designed by synthesizing b-cyclodextrin (CD) functionalized graphene (CD/GN) hybrid as simultaneously sensing platform and signal transducer coupled with rhodamine b (RhB) as probe. In brief, GN offers large surface area and high conductivity, while CD exhibits superior host-guest recognition capability, thus the primary antibody (Ab1) of HCG can be bound into the cavities of CD/GN to form stable Ab1/CD/GN inclusion complex; meanwhile, the secondary antibody (Ab2) and RhB can also enter into the cavities, producing RhB/Ab2/CD/GN complex. Then, by using Ab1/ CD/GN as sensing platform and RhB/Ab2/CD/GN as signal transducer (in which RhB was signal probe), a simple sandwich-type immunosensor was constructed. Under the optimum parameters, the designed immunosensor exhibited a considerable low analytical detection of 1.0 pg mL&lt;sup&gt;−1&lt;/sup&gt; and a wide linearity of 0.002 to 10.0 ng mL&lt;sup&gt;−1&lt;/sup&gt; for HCG, revealing the developed sandwich-type electrochemical immunosensing platform offered potential real applications for the determination of HCG.

Electrochemical Immunosensor for Early Detection of β-Amyloid Alzheimer's Disease Biomarker Based on Aligned Carbon Nanotubes Gold Nanocomposites.

Beta-amyloid (βA) peptides accompanying the physiological change in brain induce Alzheimer's disease. In this work, a highly sensitive electrochemical (EC) immunosensor platform has been developed for the quantitative detection of βA peptides, using the gold nanoparticle functionalized chitosan-aligned carbon nanotube (CS-aCNT-Au) nanocomposites on glassy carbon electrodes (GCE). The immunosensor has been fabricated by immobilization of the anti-βA antibody upon CS-aCNT-Au/GCE. In the CS-aCNT nanocomposite, CS has high biocompatibility. Hydroxy and amine functionalities favor the antibody immobilization and prevent the leaching of nanocomposites of the modified electrode due to the adhesive environment. Moreover, aCNT offers high conductivity, stability, and a large surface area (the calculated effective surface area of the CS-aCNT/GCE is 8.594 × 10-2 cm2). However, the incorporation of AuNPs further enhances the conductivity of the CS-aCNT-Au nanocomposite based on differential pulse voltammetry (DPV) results, and also improves the effective surface area (9.735 × 10-2 cm2). The surface morphology and electrochemical studies of the nanocomposite, as well as its modifications by the anti-βA antibody and BSA, were carried out through field emission scanning electron microscope (FESEM), cyclic voltammetry (CV), and DPV. The quantitative immunosensing of the βA in phosphate-buffered saline (PBS) solution is accomplished via DPV, which reveals that the immunosensor has a high sensitivity of 157.60 µA pg-1 mL cm-2 and a broad detection range of 10.0 pg mL-1-100.0 µg mL-1, with a limit of detection (LOD) of 0.87 pg mL-1. Subsequently, we detected the spiked βA in diluted serum with a linear detection range of 10.0 pg mL-1-1.0 ng mL-1 and LOD of 0.95 pg mL-1. Moreover, a selectivity study exhibited a high affinity of immunosensors towards βA. Thus, we propose that this highly efficient immunosensor can potentially be applied for the point-of-care (POC) sensing of βA in clinical samples.

Development and clinical evaluation of commercial glucose meter coupled with nanofiber based immuno-platform for self-diagnosis of SARS-CoV-2 in saliva

Rapid diagnostics for the diagnosis of COVID-19 are urgently needed in offices, residences, and other public places due to the new Covid epidemic stages. A portable and easy-to-use immunosensing platform was developed and evaluated for a point-of-care and self-detection of SARS-CoV-2 spike protein without the need for extraction, separation, or amplification steps using clinically isolated samples (n = 40 samples). The sensing platform was fabricated based on functionalized nylon nanofibrous membranes and a commercial glucose meter to enable easy deployment of the sensing technology. The fabrication of the immunoreaction vial using nylon nanofibrous membranes as a support matrix for the tethering of antibodies significantly improved the sensitivity of the detection platform in contrast to the use of conventional nylon casted membranes. The sensitivity of the nanofibrous membrane attached antibody was at least an order of magnitude higher (∼12 times) compared to the sensitivity of detection with regular casted membrane-based immunoreaction vial. The feasibility of the designed sensing platform was investigated using saliva as a non-invasive and self-administered sample for the diagnosis of SARS-CoV-2. With a detection limit of 9 ng mL−1 and no pretreatment processes required, the sensing platform demonstrated its suitability for the direct detection of SARS-CoV-2 spike protein in the spiked saliva samples. In addition, the developed platform depicted high agreement with RT-qPCR data in the analysis of the clinical samples with good stability over the storage time and reusability for three cycles with maintaining more than 95% of its original activity.

Sensitive electrochemical sensing platform based on Au nanoflower-integrated carbon fiber for detecting interleukin-6 in human serum

Prostate cancer (PCa) is the most prevalent cancer worldwide, with a high mortality rate. The early and accurate detection of PCa is critical in reducing mortality and saving lives. Timely diagnosis can improve the chances of successful treatment using advanced technologies. In recent years, nanomaterial-based electrochemical sensing strategies have been adopted in clinical diagnosis, as they allow sensitive early-biomarker detections to be converged with a cost-effective electronic readout system. Herein, we present a flexible electrochemical immunosensor platform for detecting interleukin-6 (IL-6) based on an Au-integrated flexible carbon fiber (Au/CF) electrode prepared via electrodeposition and chemically modified to capture IL-6 antibodies. Several techniques are used to analyze the prepared Au/CF composite electrodes to confirm their morphology, structure, and elemental composition. Under optimum conditions, the fabricated immunosensor exhibits a wide linear dynamic ranging from 1 fg/mL to 1 μg/mL and a low detection limit of 0.056 fg/mL, with a sensitivity of 62.17 μA/(fg mL−1). The proposed fiber-based immunosensor is used to quantify the concentration of IL-6 in serum samples from clinical PCa patients (T3b and T4 stages), and the results are validated using the commercial Meso Scale Diagnostics (MSD) V-Plex method. The acceptable results yielded by the proposed immunosensor indicate that it can serve as a new platform to realize highly sensitive and cost-effective diagnostic strategies for the early diagnosis of PCa.

Fabrication of a Disposable Electrochemical Immunosensor Based on Nanochannel Array Modified Electrodes and Gated Electrochemical Signals for Sensitive Determination of C-Reactive Protein.

Sensitive determination of C-reactive protein (CRP) is of great significance because it is an early indicator of inflammation in cardiovascular disease and acute myocardial infarction. A disposable electrode with an integrated three-electrode system (working, reference, and counter electrodes) has great potential in the detection of biomarkers. In this work, an electrochemical immunosensing platform was fabricated on disposable and integrated screen-printed carbon electrode (SPCE) by introducing nanochannel arrays and gated electrochemical signals, which can achieve the sensitive detection of CRP in serum. To introduce active reactive groups for the fabrication of immuno-recognitive interface, vertically-ordered mesoporous silica-nanochannel film (VMSF) with rich amino groups (NH2-VMSF) was rapidly grown by electrochemical assisted self-assembly (EASA). The electrochemically reduced graphene oxide (ErGO) synthesized in situ during the growth of NH2-VMSF was used as a conductive adhesive glue to achieve stable bonding of the nanochannel array (NH2-VMSF/ErGO/SPCE). After the amino group on the outer surface of NH2-VMSF reacted with bifunctional glutaraldehyde (GA/NH2-VMSF/ErGO/SPCE), the converted aldehyde surface was applied for covalent immobilization of the recognitive antibody (Ab) followed with the blocking of the non-specific sites. The fabricated immunosensor, Ab/GA/NH2-VMSF/ErGO/SPCE, enables sensitive detection of CRP in the range from 10 pg/mL to 100 ng/mL with low limit of detection (LOD, 8 pg/mL, S/N = 3). The immunosensor possessed high selectivity and can realize reliable determination of CRP in human serum.

Multifunctional porphyrin-ionic liquid aggregate for highly sensitive electrochemical detection of protein

Herein, this paper describes a novel label-free and extensibility electrochemical sensing platform based on porphyrin-ionic liquid (Por-IL) aggregate for the detection of antibody. The Por-IL was synthesized with water-soluble porphyrins Zn(II) meso-tetrakis (4-sulfonatophenyl)porphyrin (ZnTPPS)) and the ionic liquid 1-decyl-alkyl-3-methylimidazolium bromide (C10mimBr) under room temperature, which exhibited high singlet oxygen (1O2) quantum yields and electrocatalytic activity toward hydrogen peroxide (H2O2). In the presence of antibody, the antibody could be introduced on the surface of the electrode on the basis of antigen-antibody biorecognition. Under light illumination, the 1O2 formed, then water and the formed 1O2 could be catalyzed by antibody via the antibody catalyzed water oxidation pathway to produce H2O2 which could be detected by the electrode, leading to the electrochemical signal for readout. Using anti-carcinoembryonic antigen (anti-CEA) as a model target, this method displayed a wide linear detection range and a lower detection limit. In particular, Por-IL demonstrated lower detection limit of 1.67 fg/mL. Furthermore, the Por-IL sensors were able to detect antibody in complex samples. The immunosensor platform has the features of label-free, sensitivity, only with air and on/off light switching and could be used to detect of a variety of antibody by using corresponding antigen, showing potential application in medical diagnosis.

Sensitive Zika biomarker detection assisted by quantum dot-modified electrochemical immunosensing platform

We report the development of a new nanostructured electrochemical immunosensing platform for the detection of the Zika virus envelope protein (EP-ZIKV). For this, quantum dots (QDs) were explored in combination with screen-printed carbon electrodes (SPCEs) functionalized with a conductor polymeric film, formed from 2-(1H-pyrrol-1-yl)ethanamine (Pyam), and anti-EP DIII ZIKV antibodies. Carboxylated CdTe QDs were synthesized, characterized by optical and structural techniques, and covalently immobilized onto the SPCE/PPyam surface. Then, anti-EP ZIKV antibodies were also covalently conjugated to QDs. All stages of platform assembly were evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The detection of EP-ZIKV was performed by differential pulse voltammetry (DPV). Results indicated that QDs were efficiently immobilized, and did not show oxidation, under the conditions evaluated, for at least 7 months. Anti-EP ZIKV antibodies were effectively immobilized on the PPyam/QDs surface, even after 2 months of electrode storage. The platform enabled the detection of EP-ZIKV with high sensitivity using minimal sample volumes (LOD = 0.1 ng mL-1 and LOQ = 0.4 ng mL-1). The platform was also able to detect EP-ZIKV in spiked serum samples. Moreover, the platform showed specificity, not detecting the EP-DENV 3 nor a mixture of four DENV serotypes antigens. Thus, the proposed combination favored the development of a sensitive immunosensing platform, promising for the detection of Zika in the viremic phase, which also holds potential for transposition to other arboviruses.

Chitosan/genipin modified electrode for voltammetric determination of interleukin-6 as a biomarker of sepsis

Ultrasensitive electroanalytical monitoring of interleukin-6 levels in serum samples has emerged as a valuable tool for the early diagnosis of inflammatory diseases. Despite its advantages, there is a lack of strategies for the label-free voltammetric determination of cytokines. Here, a novel chitosan/genipin modified fluorine tin oxide electrode was developed providing an in-situ hydrogel formation (FTO/CSG). This platform was applied for the detection of interleukin-6, a major pro-inflammatory cytokine. Transmission electron microscopy (TEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) indicated genipin serves as an efficient green cross-linker to build the immunosensing platform (FTO/CSG/anti-IL-6). EIS showed an increase in charge transfer resistance from 326 to 1360 kΩ after the immobilization of anti-IL-6 antibodies. By square wave voltammetry, this method achieved a detection limit of 0.03 pg mL−1 with a wide linear range of 0.05–1000 pg mL−1. Additionally, it displayed a high selectivity index when tested in the presence of three inflammatory cytokines as interfering proteins: IL-12, IL-1β, and TNF-α. The sample matrix effect showed a peak current variation lower than 5 %. The novel method was applied for the quantification of IL-6 in serum samples of septic mice. No statistical differences were observed between the standard ELISA and the proposed method using a confidence level of 95 %.

Disposal Immunosensor for Sensitive Electrochemical Detection of Prostate-Specific Antigen Based on Amino-Rich Nanochannels Array-Modified Patterned Indium Tin Oxide Electrode.

Sensitive detection of prostate-specific antigens (PSA) in serum is essential for the prevention and early treatment of prostate cancer. Simple and disposable electrochemical immunosensors are highly desirable for screening and mobile detection of PSAs in high-risk populations. Here, an electrochemical immunosensor was constructed based on amino-rich nanochannels array-modified patterned, inexpensive, and disposable indium tin oxide (ITO) electrodes, which can be employed for the sensitive detection of PSA. Using an amino-group-containing precursor, a vertically ordered mesoporous silica nanochannel film (VMSF) containing amino groups (NH2-VMSF) was rapidly grown on ITO. When NH2-VMSF contained template surfactant micelle (SM), the outer surface of NH2-VMSF was directionally modified by aldehyde groups, which enabled further covalent immobilization of the recognitive antibody to prepare the immuno-recognitive interface. Owing to the charge-based selective permeability, NH2-VMSF can electrostatically adsorb negatively charged redox probes in solution (Fe(CN)63-/4-). The electrochemical detection of PSA is realized based on the mechanism that the antigen-antibody complex can reduce the diffusion of redox probes in solution to the underlying electrode, leading to the decrease in electrochemical signal. The constructed immunosensor can achieve sensitive detection of PSA in the range from 10 pg/mL to 1 μg/mL with a limit of detection (LOD) of 8.1 pg/mL. Sensitive detection of PSA in human serum was also achieved. The proposed disposable immunosensor based on cheap electrode and nanochannel array is expected to provide a new idea for developing a universal immunosensing platform for sensitive detection of tumor markers.