Detection Of Human Immunoglobulin G Research Articles

Tri-signal CdS@SiO2 nanoprobes for accurate and sensitive detection of human immunoglobulin G with enhanced flexibility and internal validation

Accurate and sensitive determination of human immunoglobulin G (HIgG) level is critical for diagnosis and treatment of various diseases, including rheumatoid arthritis, humoral immunodeficiencies, and infectious disease. In this study, versatile tri-signal probes were developed by preparing CdS@SiO2 nanorods that integrate photoluminescence (PL), multi-phonon resonant Raman scattering (MRRS) and infrared absorption (IRA) properties. Through the coating of multiple CdS nanoparticles as cores within SiO2 shells, the PL and MRRS properties of CdS were improved, resulting in a significantly lowered limit of detection (LOD), with the lowest LOD of 12.37 ag mL−1. Integration with the distinctive IRA property of SiO2 shells widened the detection range towards higher concentrations, establishing a final linear range of 50 ag mL−1 to 10 μg mL−1. The remarkable consistency among the three signals highlighted the robust internal verification capability for accurate detection. This approach enhances flexibility in selecting detection methodologies to suit diverse scenarios, facilitating HIgG detection. The tri-signal nanoprobes also exhibited excellent detection selectivity, specificity and repeatability. This study presents a fresh idea for developing high-performance detection strategies.

Target-induced photoelectrochemistry and colorimetric dual-mode platform for HIgG based on Ag2S/SnO2 composites and CoOOH nanoflakes

Human immunoglobulin G (HIgG) plays a significant role in diagnosing infections and monitoring autoimmune diseases. However, the development of sensitive and reliable sensing platforms remains a challenge. Based on the Ag2S/SnO2 composites, a dual-mode sensing platform was developed using multifunctional CoOOH nanoflakes for the sensitive detection of HIgG through photoelectrochemistry (PEC) and colorimetry. In the PEC mode, Ag2S QDs boost the PEC activity of SnO2 NFs and facilitate the subsequent antibody immobilization. Ascorbic acid (AA) captures holes in Ag2S/SnO2 to enhance the photocurrent. CoOOH, acting as a secondary antibody label, forms a sandwich structure with the electrode. The loading of HIgG and CoOOH-Ab2 due to specific recognition of antigen-antibody, leads to the quenching of PEC signal. Various amounts of HIgG will bind with different amounts of CoOOH-Ab2, displaying a linear response within the range of 100 pg/mL∼10 μg/mL, with the detection limit of 2.2 pg/mL. In the colorimetric mode, CoOOH efficiently catalyzes the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB), and various amount of the sandwich biocomplexes formed with different HIgG levels lead to distinct color changes for visual detection. The linear response range is 500 pg/mL∼9.375 μg/mL with a lower detection limit of 0.29 ng/mL. The two independent modes with different mechanisms, based on the same PEC electrode, can validate each other and provide more scientific and reliable results in response to the targets. Thus, this dual-mode sensing platform for targets-induced signaling changes presents a novel strategy for bioanalysis and detection.

4-(Triethoxysilyl)butanoic acid as a self-assembled monolayer for surface modification of titanium dioxide.

In this study, the carboxy silane 4-(triethoxysilyl)butanoic acid (TESBA) was used to modify titanium dioxide (TiO2) to create a self-assembled monolayer (SAM) and then directionally immobilize a capture antibody using protein A. We selected the amino silane (3-aminopropyl)triethoxysilane (APTES) to perform a comparative analysis with TESBA, and employed glutaraldehyde (GA) as the control. The modification and detection effects and the limit of detection (LOD) were evaluated by detecting human immunoglobulin G (IgG). The average normalized sensitivity of the dual-grating coupler waveguide biosensor was 49.63 ± 0.27 RIU-1 and the optimum resolution was 1.30 × 10-6 RIU. When the SAM was prepared using TESBA and APTES followed by GA, the LOD was 4.59 × 10-7 g mL-1 and 5.29 × 10-7 g mL-1, respectively. We analyzed the modification and detection effects by the t-test and concluded that the differences in the modification effects using TESBA and APTES followed by GA were significant and the differences in the detection effects using TESBA and APTES followed by GA were insignificant. The use of TESBA as the SAM led to the modification effect being superior to that obtained using APTES followed by GA. The detection effect using TESBA was as outstanding as that using APTES followed by GA. Our findings demonstrate the feasibility and effectiveness of using TESBA as the SAM to carboxylate the surface of TiO2, thereby enabling immobilization of biomolecules for human IgG detection.

Chemical Redox Cycling in an Organic Photoelectrochemical Transistor: Toward Dual Chemical and Electronic Amplification for Bioanalysis.

The organic photoelectrochemical transistor (OPECT) has been proven to be a promising platform to study the rich light-matter-bio interplay toward advanced biomolecular detection, yet current OPECT is highly restrained to its intrinsic electronic amplification. Herein, this work first combines chemical amplification with electronic amplification in OPECT for dual-amplified bioanalytics with high current gain, which is exemplified by human immunoglobulin G (HIgG)-dependent sandwich immunorecognition and subsequent alkaline phosphatase (ALP)-mediated chemical redox cycling (CRC) on a metal-organic framework (MOF)-derived BiVO4/WO3 gate. The target-dependent redox cycling of ascorbic acid (AA) acting as an effective electron donor could lead to an amplified modulation against the polymer channel, as indicated by the channel current. The as-developed bioanalysis could achieve sensitive HIgG detection with a good analytical performance. This work features the dual chemical and electronic amplification for OPECT bioanalysis and is expected to stimulate further interest in the design of CRC-assisted OPECT bioassays.

Multiple protein-patterned surface plasmon resonance biochip for the detection of human immunoglobulin-G.

A portable surface plasmon resonance (SPR) measurement prototype integrated with a multiple protein-patterned SPR biochip is introduced for label-free and selective detection of human immunoglobulin-G (H-IgG). The polyclonal anti-H-IgG antibodies derived from goat, rabbit, and mouse were immobilized through polydimethylsiloxane (PDMS) microchannels to fabricate the patterned SPR biochip. The PDMS surface was functionalized using 3-aminopropyltrimethoxysilane and bonded to carbodiimide-activated gold substrates to construct irreversibly bonded hydrophilic microfluidic chip at room temperature. For SPR measurement, a custom-made system is developed with a high angular scanning accuracy of 0.005° and a wide scanning range of 30°-80° that avoids the conventional requirement of expensive goniometric stages and detector arrays. The SPR biochip immobilized with 750μg/mL goat anti-H-IgG demonstrated detection of H-IgG with a detection limits of 15 μg/mL, and linear response through a wide concentration range (15-225 μg/mL) of high coefficient of determination (R2 =0.99661). The selectivity of the sensor was investigated by exposing them to two different non-specific targets (bovine serum albumin and polyvalent antivenom). The results indicate negligible sensor response towards nonspecific targets (0.25° for 30 μg/mL bovine serum albumin (BSA) and 0.25° for 30 μg/mL polyvalent antivenom) in comparison to H-IgG (1.5° for 30 μg/mL).

Alkaline Phosphatase-Mediated Bioetching of CoOOH/BiVO4 for Signal-On Organic Photoelectrochemical Transistor Bioanalysis.

Organic photoelectrochemical transistor (OPECT) bioanalytics has recently appeared as a promising route for biological measurements, which has major implications in both next-generation photoelectrochemical (PEC) bioanalysis and futuristic biorelated implementations. Via biological dissociation of materials, bioetching is a useful technique for bio-manufacturing and bioanalysis. The intersection of these two domains is expected to be a possible way to achieve innovative OPECT bioanalytics. Herein, we validate such a possibility, which is exemplified by alkaline phosphatase (ALP)-mediated bioetching of a CoOOH/BiVO4 gate for a signal-on OPECT immunoassay of human immunoglobulin G (HIgG) as the model target. Specifically, target-dependent bioetching of the upper CoOOH layer could result into an enhanced electrolyte contact and light accessibility to BiVO4, leading to the modulated response of the polymeric poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) channel that could be monitored by the channel current. The introduced biosensor achieves sensitive detection of HIgG with high selectivity and sensitivity. This work features bioetching-enabled high-efficacy OPECT bioanalysis and is anticipated to serve as a generic protocol, considering the diverse bioetching routes.

Photoluminescent and multi-phonon resonance Raman scattering dual-mode immunoassays based on CdS nanoparticles for HIgG detection.

A dual-mode immunoassay strategy based on CdS nanoparticles as signal probes with both of photoluminescent (PL) and multi-phonon resonance Raman scattering (MRRS) properties was developed. Simplified structural design and preparation were achieved due to the intrinsic integration of PL and MRRS dual signals in the single-unit CdS nanoprobes. Human immunoglobulin G (HIgG) was sensitively and specifically detected using the proposed PL-MRRS dual-mode strategy. The linear relationship between the HIgG concentration and the intensity of 707nm PL peaks/300cm-1 MRRS peaks under the excitation of 488nm laser wasestablished. The limit of detection was 0.93fgmL-1 for PL and 1.10fgmL-1 for MRRS. In comparison with previous IgG detection methods, the proposed method exhibited prominent advantages in detection sensitivity and workingrange with good stability and repeatability. An internal self-calibration was realized which ensured the accuracy and reliability of detection results. Both results of specificity experiments and serum sample analysis further confirmed the feasibility of thedesigned immunoassay strategy in practical serological detection.

Paper-Based Microfluidic Devices: Low-Cost Platforms for Rapid Biochemical Detection.

We developed low-cost, portable paper-based diagnostic devices for detection of human immunoglobulin M (IgM) and immunoglobulin G (IgG) in serum without any sample preparation. These devices can be used to help identify presence of diseases, used to provide rapid results (<5 minutes), readily used by untrained personnel, employed in austere environments, configured to obtain multiplexed assays, and easily disposed of. We successfully accomplished colorimetric detection of human IgG and human IgM using a sandwich-style assay within the microfluidic paper device via vertical flow immunoassay configuration. The reaction zone in the wax printed paper layer is a small circular pattern. Gold nanoparticles conjugated with anti-human IgG and IgM antibodies have been used for colorimetric detection of IgG or IgM by naked eye. Colorimetric signal can be precisely quantified through implementation of image analysis software which can be developed as an app for a smartphone. The size of the device is 2 cm × 2 cm × 1 mm. Colorimetric detection of human IgG was accomplished at 100 fg/mL concentration using a gold nanoparticle-conjugated anti-human IgG antibody. The developed platform has a dynamic range of IgM and IgG concentrations between 0.1 pg/mL and 100 μg/mL. These devices provided a color readout in <5 minutes using 20 µL of serum. We also demonstrated that the devices show a significant degree of ruggedness and temperature stability as they were able to provide satisfactory results (detection of 0.1 pg/mL IgG) after 14 days of long stability and shelf-life experiment at an elevated temperature of at least 50 ˚C-the shelf life can be as long as 180 days under ambient conditions for detection of 100 µg/mL IgG. Because of the inherent simplicity of the device operation and their ease of use, there is no variation between samples and users of the device. This low-cost approach enables multiplexing with >1 measurement performed in parallel at the same time. We anticipate that because of the sensitivity, specificity, ease of use, and overall reliability, this approach will become a standard for diagnosis of diseases and health conditions.

AuNP array coated substrate for sensitive and homogeneous SERS-immunoassay detection of human immunoglobulin G.

Owing to the high sensitivity, fast responsiveness and high specificity, immunoassays using surface-enhanced Raman scattering (SERS) as the readout signal displayed great potential in disease diagnosis. In this study, we developed a SERS-immunoassay method for the detection of human immunoglobulin G (HIgG). Upon involving well-ordered AuA on a SERSIA substrate, the LSPR effect was further enhanced to generate a strong and uniform Raman signal through the formation of sandwich structure with the addition of target HIgG and SERSIA tag. Optimization of the assay provided a wide linear range (0.1–200 μg mL−1) and low limit of detection (0.1 μg mL−1). In addition, the SERS-immunoassay method displayed excellent specificity and was homogeneous, which guaranteed the practical use of this method in the quantitative detection of HIgG. To validate this assay, human serum was analysed, which demonstrated the potential advantages of SERS-immunoassay technology in clinical diagnostics.

An Optical Fiber Immunosensor With a Low Detection Limit Based on Plasmon Coupling Enhancement

An optical fiber immunosensor with a low detection limit based on plasmon coupling enhancement is proposed for detecting human immunoglobulin G (IgG). Graphene oxide (GO)-gold nanorod composites are synthesized and modified onto a photonic crystal fiber (PCF) surface coated with a Au film. GO, as a biosensitive layer, is used to decorate the gold nanorods and concentrate target molecules. The experimental result indicates that the refractive index sensitivity is drastically enhanced to 22248 nm/RIU because of plasmon coupling. Correspondingly, the human IgG detection limit decreases to 6 ng/mL. Moreover, the PCF is insensitive to temperature fluctuation, which can further reduce the measurement error.

A dual channel self-compensation optical fiber biosensor based on coupling of surface plasmon polariton

We propose a dual-channel fiber-optic biosensor based on electronic field coupling between surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR). One sensing channel is coated with a bilayer of graphene oxide/Au, whose surface is modified with goat anti-human immunoglobulin G (IgG) to detect human IgG labeled with Au nanoparticles (Au NPs). The graphene oxide film in the region of the coupled electric fields increases the loading of biomolecules on the sensor surface and the immunological response. This sandwich structure can make full use of the coupled electric field excited by Au film and Au NPs, compared to the traditional LSPR sensor. The other sensing channel is coated only with Ag film as a reference channel to eliminate measurement error caused by non-specific binding and temperature cross-sensitivity. We numerically investigate the electric field coupling strength of SPR/LSPR and conducted corresponding experiments. The sensor had a high refractive index sensitivity with 13,592 nm/RIU and limit of detection of human IgG can be reduced to 15 ng/mL, which is 15.3 times lower than that of conventional SPR sensors. The proposed biosensor has sensing superiorities of high sensitivity, accuracy and temperature insensitive.

Highly Sensitive SPR Biosensor Based on Graphene Oxide and Staphylococcal Protein A Co-Modified TFBG for Human IgG Detection

A highly sensitive optical fiber surface plasmon resonance (SPR) biosensor based on graphene oxide (GO) and staphylococcal protein A (SPA) co-modified tilted fiber Bragg grating (TFBG) is proposed and demonstrated for the detection of human immunoglobulin G (IgG) for the first time. The gold film on the surface of the sensor was first fixed with GO and then modified with an SPA to improve the sensitivity of the sensor. Large specific surface area and abundant functional groups of GO can adsorb more antibodies. The combination of SPA and the antibody molecule Fc region makes the Fab area with antigen-binding sites extend outward, resulting in highly oriented antibody immobilization on the sensor surface and high antigen–antibody binding efficiency. The experimental results show that the sensitivity as well as the limit of detection of GO-SPA-modified TFBG-SPR biosensor is around 0.096 dB/( $\mu \text{g}$ /mL) and $0.5~\mu \text{g}$ /mL, showing better responses to human IgG solutions with a concentration range of 30– $100~\mu \text{g}$ /mL compared with the TFBG-SPR biosensors modified singly with GO or SPA. The biosensor exhibits the advantages of small size, ease of fabrication, high sensitivity, label-free, and rapid response, and provides a new solution for detecting low concentration of biological solution, presenting great application potential in the biochemistry field.

Multimode-coreless-multimode fiber biosensor based on surface plasmon resonance

This study presents a facile, rapid and effective method for the fabrication of optical fiber surface plasmon resonance biosensors. A section of coreless fiber is spliced between two multimode fibers to construct a multimode-coreless-multimode (MCM) fiber structure. We take full advantage of the transmission characteristics of the coreless fiber, and the experimental results confirm that this MCM after coating with a thin gold film is able to excite surface plasmon wave effectively. Three sensors with different lengths of coreless optical fibers of 1 cm, 1.6 cm and 2 cm were constructed. And when the refractive index (RI) of the sucrose solution changes from 1.33 to 1.3883, the RI sensitivity was measured to be 2129.66 nm/RIU, 2249.33 nm/RIU and 2307.93 nm/RIU, respectively. After a comprehensive comparison, we chose the MCM optical fiber sensor with a coreless fiber length of 1.6 cm for biological experiments. After directly immobilized the antibody on the gold film, the biosensor was able to selective detect human immunoglobulin G (HIgG) with a sensitivity of 215 nm/ (mg ml−1). The limit of detection is 0.465 µg ml−1. The biosensor exhibited effective antibody immobilization ability and high sensitivity for HIgG detection, which fully demonstrates its potential applications in the broader biomedical or chemical field.

Voltammetric immunoassay of human IgG based on the release of cadmium(II) from CdS nanocrystals deposited on mesoporous silica nanospheres.

The authors describe a nanocomposite that was obtained by in-situ deposition of CdS nanocrystals on mesoporous silica nanospheres (MSNs), and its use in an electrochemical immunoassay of human immunoglobulin G (HIgG). The MCN/CdS nanocomposite was covalently modified with the antibodies against HIgG and then employed in a voltammetric immunoassay at antibody-functionalized magnetic beads. Through sandwich immunoreaction, the MCN/CdS nanoprobes are quantitatively captured onto the magnetic beads where numerous Cd(II) ions are released in an acidic solution. The Cd(II) can be detected by anodic stripping voltammetry at a typical working potential of -0.78V (vs. Ag/AgCl). In combination with the high loading of CdS on MSNs, the use of the stripping voltammetric analysis renders the method high sensitivity. A wide linear range varying from 0.01 to 100ngmL-1 is obtained for HIgG detection with a lower detection limit at 2.9pgmL-1. In addition, the preparation of the nanoprobe is inexpensive. The magnetic bead-based assay does not require complex manipulations. Therefore, this method is deemed to possess a wide scope in that it may be applied to other immunoassays. Graphical abstract Graphical Abstract contains poor quality and small text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.A TIFF file at 900 dpi resolution of the Graphical Abstract has been attached via this online system. Schematic presentation of the preparation of the mesoporous silica nanosphere (MSN)/CdS nanocomposite for the electrochemical immunoassay of human IgG at magnetic beads. The high decoration of CdS on MSN and the stripping voltammetric analysis of Cd(II) ions render the method high sensitivity.

Iodine-Mediated Etching of Gold Nanorods for Plasmonic ELISA Based on Colorimetric Detection of Alkaline Phosphatase.

Here, we propose a plasmonic enzyme-linked immunosorbent assay (ELISA) based on highly sensitive colorimetric detection of alkaline phosphatase (ALP), which is achieved by iodine-mediated etching of gold nanorods (AuNRs). Once the sandwich-type immunocomplex is formed, the ALP bound on the polystyrene microwells will hydrolyze ascorbic acid 2-phosphate into ascorbic acid. Subsequently, iodate is reduced to iodine, a moderate oxidant, which etches AuNRs from rod to sphere in shape. The shape change of AuNRs leads to a blue-shift of longitudinal localized surface plasmon resonance. As a result, the solution of AuNRs changes from blue to red. Benefiting from the highly sensitive detection of ALP, the proposed plasmonic ELISA has achieved an ultralow detection limit (100 pg/mL) for human immunoglobulin G (IgG). Importantly, the visual detection limit (3.0 ng/mL) allows the rapid differential diagnosis with the naked eye. The further detection of human IgG in fetal bovine serum indicates its applicability to the determination of low abundance protein in complex biological samples.

Silver deposition directed by self-assembled gold nanorods for amplified electrochemical immunoassay

A novel electrochemical immunoassay was developed based on the signal amplification strategy of silver deposition directed by gold nanorods (AuNRs), which was in-situ assembled on the sandwich immunocomplex. The superstructure formed by the self-assembly of AuNRs provided abundant active sites for the nucleation of silver nanoparticles. In this pathway, the stripping current of silver was greatly enhanced. Using human immunoglobulin G (HIgG) as a model analyte, the ultrasensitive immunoassay showed a wide linear range of six orders of magnitude from 0.1 fg mL−1 to 100 pg mL−1, with the low detection limit down to 0.08 fg mL−1. The practicality of this electrochemical immunoassay for detection of HIgG in serum was validated with the average recovery of 93.9%. In addition, this enzyme-free immunoassay also has the advantages of acceptable reproducibility and specificity, and thus this immunosensing protocol can be extended to the detection of other low-abundant protein biomarkers.

A double signal electrochemical human immunoglobulin G immunosensor based on gold nanoparticles-polydopamine functionalized reduced graphene oxide as a sensor platform and AgNPs/carbon nanocomposite as signal probe and catalytic substrate

In this paper, a double signal electrochemical Human immunoglobulin G (HIgG) immunosensor based on AgNPs/carbon nanocomposite (Ag/C NC) as the signal probe and catalytic substrate was developed for fast and sensitive detection of HIgG. The as-prepared AuNPs-PDA-rGO nanocomposite and Ag/C NC were confirmed by UV–vis, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. Electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical properties of the proposed immunosensor. The AuNPs-PDA-rGO nanocomposite can improve the electron transfer rate and capture more Ab1. In the sandwich-type immunoassay process, the Ag/C NC functionalized bioconjugates were captured on HIgG/Ab1/AuNPs-PDA-rGO surface and the electrochemical double-signal strategy was employed. These double electrochemical detection signals were directly monitored the oxidation current originated from Ag/C NC and indirectly detected the reduction current of benzoquinone which was produced from the reaction of H2O2 and HQ by catalysis of Ag/C NC in electrochemical detection of HIgG. Under the optimized conditions, the current responses were changed with the concentrations of HIgG for the proposed immunosensor with wide linear ranges of 0.1 to 100ngmL−1 and 0.01–100ngmL−1 with the lowest detection concentration of 0.001ng mL−1 in the absence and presence of H2O2 and HQ. The double-signal strategy is used for detection of HIgG, and the results came from the two signals were well consistent with each other. The proposed immunosensor was successfully applied in analysis of human IgG in real samples and this strategy may provide a relative simple and effective method for construction of other immunsensors in detection of other biomarkers in clinical medicine.

Sensing Diffraction Gratings of Antigen‐Responsive Hydrogel for Human Immunoglobulin‐G Detection

Sensing diffraction gratings of antigen-responsive hydrogel were developed for human immunoglobulin-G (H-IgG) detection. The IgG-sensing gratings were fabricated by soft lithographic duplication of photoinduced surface relief gratings on azo polymer films to the hydrogel surfaces. The quantitative detection of H-IgG was achieved by detecting modulation of the diffraction efficiency when the gratings were exposed to antigen solutions. The gratings showed high sensitivity and specificity for the H-IgG detection. The detection could be performed at a reasonably fast rate with good reusability. In the process, no fluorophore labeling or additional signal enhancement was required.

HIgG Detection by Histidine Carrying AFM Tips (Cantilevers)

"Atomic Force Microscope" (AFM) tips (cantilevers) carrying a pseudo-specific ligand, i.e., histidine were prepared and investigated for detection of Human Immunoglobulin-G (HIgG) in aqueous media. The AFM tips (cantilevers) were first treated with HNO(3) and silanized to create amino groups; then glutaraldehyde (GA) was bonded via these surface amino groups; and finally, histidine molecules were immobilized by reaction of the amino groups of histidine with the free aldehyde groups of GA. Optimal immobilization conditions were described. Immobilizations were observed both by optical and confocal laser scanning microscopy. Interactions between the histidine carrying AFM tips (cantilevers) and the aqueous medium containing HIgG with different concentrations were quantified by "the separation distance" measured with the AFM system as the main variable. A quite nice linear correlation between the HIgG concentration and the separation distance was measured with AFM system. Interactions were also followed by an alternative "Modified Lowry" method, in which similar behavior was observed. We were able to measure HIgG concentration in aqueous media down to 0.055 pmol/micro l (8 mg/dl) concentration with this AFM based novel immunosensor.