Channel and Substrate Zone Two-Dimensional Resolution for Chemiluminescent Multiplex Immunoassay

Application of Various Optical and Electrochemical Nanobiosensors for Detecting Cancer Antigen 125 (CA-125): A Review

Nowadays, diagnosing early-stage cancers can be vital for saving patients and dramatically decreases mortality rates. Therefore, specificity and sensitivity in the detection of cancer antigens should be elaborately ensured. Some early-stage cancers can be diagnosed via detecting the cancer antigen CA-125, such as ovarian cancer, and required treatments can be applied more efficiently. Thus, detection of CA-125 by employing various optical or electrochemical biosensors is a preliminary and crucial step to treating cancers. In this review, a diverse range of optical and electrochemical means of detecting CA-125 are reviewed. Furthermore, an applicable comparison of their performance and sensitivity is provided, several commercial detection kits are investigated, and their applications are compared and discussed to determine whether they are applicable and accurate enough.

Electrogenerated Chemiluminescence Immunoassays on Nanoelectrode Ensembles Platform with Magnetic Microbeads for the Determination of Carbohydrate Antigen

This work reports a gold nanoelectrode ensembles (Au-NEE) platform taken as a disposable electrogenerated chemiluminescence (ECL) platform with immunomagnetic microbeads for ECL immunoassays for the first time. The peak-shaped voltammograms were obtained at the Au-NEE, attributed to the total diffusional overlap. The ECL intensity at Au-NEE was 12.9 folds in the Ru(bpy)₃²⁺-tri-n-propylamine (TPA) ECL system and 19.6 folds in the luminol-H₂O₂ system, compared with that at the Au macroelectrode using the normalized active area of the electrodes, mainly attributed to the diffusion overlap of the Au-NEE and the edge effect of the individual gold nanodisks of the Au-NEE. The ECL immunoassay on the Au-NEE platform with magnetic microbeads for the determination of cancer biomarkers was developed. Carbohydrate antigen 19-9 (CA 19-9) was chosen as a model analyte while CA 19-9 antibody on the magnetic microbeads was taken as the capture probe, and ruthenium complex-labeled CA 19-9 antibody was used as the signal probe. A "sandwich" bioconjugates on the magnetic beads were transferred onto the ECL platform, and then the ECL measurements were performed in TPA solution. The developed method showed that the ECL peak intensity was directly in proportion to the concentration of CA 19-9 in the range from 0.5 to 20 U/mL with a limit of detection of 0.4 U/mL. This work demonstrates that the Au-NEE can be employed as a useful disposable ECL platform with the merits of cheapness, low nonspecific adsorption and practical application. The proposed approach will open a new avenue in the point-of-care test for the determination of protein biomarkers.

Plasmonic Nanobiosensing: from in situ plant monitoring to cancer diagnostics at the point of care

Nucleic acid biosensing technologies have the capability to provide valuable information in applications ranging from medical diagnostics to environmental sensing. The unique properties of plasmonic metallic nanoparticles have been used for sensing purposes and among them, plasmonic sensors based on surface-enhanced Raman scattering (SERS) offer the advantages of sensitive and muliplexed detection owing to the narrow bandwidth of their characteristic Raman spectral features. This paper describes current applications that employ the unique SERS-based inverse molecular sentinel (iMS) nanobiosensors developed in our laboratory. Herein, we demonstrate the use of label-free iMS nanoprobes for detecting specific nucleic acid biomarkers in a wide variety of applications from cancer diagnostics to genetic monitoring for plant biology in renewable biofuel research.

pH-Based Detection of Target Analytes in Diluted Serum Samples Using Surface Plasmon Resonance Immunosensor

Detection of minute quantities of target antigens in serum samples (consisting of a mixture of proteins/biomolecules) can be achieved by enhancement of the capture efficiencies of heterogeneous immunosensors. An important process parameter which affects the capture of target analytes in such immunosensors is the pH of the solution as the target proteins present in the serum samples are charged molecules. Here, we investigated the capture of prostate-specific antigens (PSAs), first in a mixed-analyte system wherein the solution contained two other non-specific proteins along with the target analyte, using the surface plasmon resonance spectroscopy. There are no reports on the detection of antigens in a mixed system based on the optimization of the pH values of the carrier fluid, and this is the motivation of the present work. Further, we studied interference effects caused by the presence of these non-specific proteins in the mixed-analyte systems by artificially increasing the ratio of the interfering proteins to that of the target protein. Eventually PSA spiked into the rabbit serum samples was captured through the optimization of the pH of the solution. We could detect PSA in the serum samples when diluted to 100 times or more, where the amounts of other interfering proteins were ~ 66 times that of the amount of PSA. This study proposes a heterogeneous immunosensor to detect the target analytes in the diluted serum samples by tuning pH the of solution mixture, which can be utilized to detect disease biomarkers in serum samples.

Simply and sensitively simultaneous detection hepatocellular carcinoma markers AFP and miRNA-122 by a label-free resonance light scattering sensor

In this study, an intelligent and label-free sensor is utilized for the first time to one-spot simultaneous detection hepatocellular carcinoma markers AFP and miRNA-122 by a resonance light scattering (RLS) sensor. cDNA1 hybridizes with cDNA2 to form double-stranded DNA (dsDNA). The construction of dsDNA and methyl violet is used to form the RLS sensor via the electronic interaction. When AFP or miRNA-122 is present, the cDNA (cDNA1 or cDNA2) can bindings of target, thereby RLS intensity changed proportionally with the concentration of AFP or that of miRNA-122. The detection limits of AFP and miRNA-122 are 0.94 μg/L and 98 pM respectively, and their good linear which ranges from 5 to 100 μg/L and 200 pM to 10 nM are achieved using the assay. In the presence of miRNA-122 and AFP mixtures, AFP bound to the AFP aptamer to increase the RLS signal, and miRNA-122 bound to the miRNA-122 complementary strand to decrease the RLS signal. The RLS signal changed in response to changing AFP and miRNA-122 concentrations, so that one-spot simultaneous detection of alpha fetal protein and miRNA-122 is achieved. This method has potential practical applications in the research of hepatocellular carcinoma.

Efficient label-free chemiluminescent immunosensor based on dual functional cupric oxide nanorods as peroxidase mimics

Dual-functional cupric oxide nanorods (CuONRs) as peroxidase mimics are proposed for the development of a flow-through, label-free chemiluminescent (CL) immunosensor. Forming the basis of this cost-efficient, label-free immunoassay, CuONRs, synthesized using a simple hydrothermal method, were deposited onto epoxy-activated standard glass slides, followed by immobilization of biotinylated capture antibodies through a streptavidin bridge. The CuONRs possess excellent catalytic activity, along with high stability as a solid support. Antigens could then be introduced to the sensing system, forming large immunocomplexes that prevent CL substrate access to the surface, thereby reducing the CL signal in a concentration dependent fashion. Using carcinoembryonic antigen (CEA) as a model analyte, the proposed label-free immunosensor was able to rapidly determine CEA with a wide linear range of 0.1-60ngmL^-1 and a low detection limit of 0.05ngmL^-1. This nanozyme-based immunosensor is simple, sensitive, cost-efficient, and has the potential to be a very promising platform for fast and efficient biosensing applications.

Lateral flow assay for carbohydrate antigen 19-9 in whole blood by using magnetized carbon nanotubes

The authors describe a rapid, low-cost and sensitive approach for the determination of carbohydrate antigen 19-9 (CA 19-9) in whole blood by using magnetized carbon nanotube (MCNT) and lateral flow strip biosensor (LFSB). MCNTs were synthesized by depositing magnetite (Fe₃O₄) nanoparticles on multiwalled carbon nanotube (CNT) via co-precipitation of ferric and ferrous ions within a dispersion of shortened multiwalled CNTs. Antibody against CA 19-9 (Ab₁) was covalently immobilized on the MCNTs and were used to capture CA 19-9 in blood. After magnetic separation, the formed MCNT-Ab₁-CA 19-9 complexes are applied to the LFSB, in which a capture antibody (Ab₂) and a secondary antibody (Ab₃) are immobilized on the test zone and control zone of the LFSB, respectively. The captured MCNTs on the test zone and control zone are producing characteristic brown bands, and this enables CA 19-9 to be visually detected. Quantitation is accomplished by reading the intensities of the bands with a portable strip reader. Under optimized conditions, the assay has a detection limit as low as 30 U⋅mL^-1 of CA19-9 in blood. This is below the cutoff value (37 U mL^-1) of CA 19-9. The assay duration for blood samples is 35 min. In our perception, the assay represents a rapid and low-cost tool for rapid determination of CA19-9 in blood that holds promise for clinical applications, particularly in limited resource settings.

An ultrasensitive multi-walled carbon nanotube–platinum–luminol nanocomposite-based electrochemiluminescence immunosensor

An ultrasensitive electrochemiluminescence (ECL) immunosensor for carbohydrate antigen 19-9 (CA19-9) detection using multi-walled carbon nanotube–platinum–luminol nanocomposites (MWCNT–Pt–luminol) as nanointerface and signal tags was designed.

A Potentiometric Addressable Photoelectrochemical Biosensor for Sensitive Detection of Two Biomarkers

It is a great challenge to fabricate multiplex and convenient photoelectrochemical biosensors for ultrasensitive determination of biomarkers. Herein, a fascinating potentiometric addressable photoelectrochemical biosensor was reported for double biomarkers' detection by varying the applied bias in the detection process. In this biosensor, the nanocomposite of cube anatase TiO₂ mesocrystals and polyamidoamine dendrimers modified a dual disk electrode as an excellent photoelectrochemical sensing matrix. Subsequently, two important biomarkers in serum for prostate cancer, prostate-specific antigen and human interleukin-6, were immobilized onto the different disks of modified electrode via glutaraldehyde bridges. Then another two photosensitizers, graphitic-carbon-nitride-labeled and CS-AgI-labeled different antibodies, were self-assembled onto the electrode surface by a corresponding competitive immune recognition reaction. The change in photocurrent with the target antigen concentration at different critical voltages enables us to selectively and quantitatively determine targets. The results demonstrated that this potentiometric addressable photoelectrochemical biosensing strategy not only has great promise as a new point-of-care diagnostic tool for early detection of prostate cancer but also can be conveniently expanded to multiplex biosensing by simply change biomarkers. More importantly, this work provides an unambiguous operating guideline of multiplex photoelectrochemical immunoassay.

Novel redox species polyaniline derivative-Au/Pt as sensing platform for label-free electrochemical immunoassay of carbohydrate antigen 199

A novel electrochemical redox-active nanocomposite was synthesized by a one-pot method using N,N'-diphenyl-p-phenylediamine as monomer, and HAuCl4 and K2PtCl4 as co-oxidizing agents. The as-prepared poly(N,N'-diphenyl-p-phenylediamine)-Au/Pt exhibited admirable electrochemical redox activity at 0.15 V, excellent H2O2 electrocatalytic ability and favorable electron transfer ability. Based on these, the evaluation of the composite as sensing substrate for label-free electrochemical immunosensing to the sensitive detection of carbohydrate antigen 199 was described. This technique proved to be a prospective detection tool with a wide liner range from 0.001 U mL(-1) to 40 U mL(-1), and a low detection limit of 2.3 × 10(-4) U mL(-1) (S/N = 3). In addition, this method was used for the analysis of human serum sample, and good agreement was obtained between the values and those of enzyme-linked immunosorbent assay, implying the potential application in clinical research. Importantly, the strategy of the present substrate could be extended to other polymer-based nanocomposites such as polypyrrole derivatives or polythiophene derivatives, and this could be of great significance for the electrochemical immunoassay.

Graphene oxide supported rhombic dodecahedral Cu2O nanocrystals for the detection of carcinoembryonic antigen

In this work, a simple electrochemical immunosensor was developed for the detection of carcinoembryonic antigen (CEA) based on rhombic dodecahedral Cu2O nanocrystals-graphene oxide-gold nanoparticles (rCu2O-GO-AuNPs). GO as the template and surfactant resulting in rCu2O exhibit improved rhombic dodecahedral structure uniformity and excellent electrochemical performance. Moreover, GO was found to be able to effectively improve the long stability of rCu2O on the electrode response. Under optimal conditions, the immunosensor showed a low limit of detection (0.004 ng ml(-1)) and a large linear range (0.01-120 ng ml(-1)). This work presents a potential alternative for the diagnostic applications of GO-supported special morphology materials in biomedicine and biosensors.

Immobilizing water-soluble graphene quantum dots with gold nanoparticles for a low potential electrochemiluminescence immunosensor

Hydrazide-modified graphene quantum dots (HM-GQDs) obtained by refluxing GQDs with hydrazine hydrate were hybridized with gold nanoparticles (AuNPs) through a redox reaction between HM-GQDs and AuCl4(-). The obtained nano-hybrids (HM-GQD-AuNPs) possess the unique electrochemiluminescence (ECL) properties of HM-GQDs and the easy self-assembly with some bio-molecules of AuNPs, which have great potential applications in bio-sensors. HM-GQD-AuNPs were modified on a glassy carbon electrode to develop a novel ECL immunosensor of carcinoembryonic antigen (CEA) as a model target analyte. Due to the increment of electron-transfer resistance after immunoreaction, the ECL intensity decreased as the concentration of CEA was increased. The linear response range was between 0.02 and 80 ng mL(-1), and the detection limit was 0.01 ng mL(-1).

Ultrasensitive simultaneous detection of four biomarkers based on hybridization chain reaction and biotin-streptavidin signal amplification strategy

A sandwich-type electrochemical immunosensor based on redox probe tags identification technology for ultrasensitive simultaneous detection of four antigens was proposed. In this project, well-distributed graphene/gold (GR-Au) hybrid film was acquired through one-step codeposition in an electrode surface and served as the base substrate for immobilizing capture antibodies (Ab1). Hybridization chain reaction (HCR) and biotin/streptavidin (B/SA), combining with gold magnetic nanoparticles were applied to increase the immobilization amount of signal tags in detection antibody (Ab2) bioconjugates. To verify this strategy, four representative biomarkers, a-fetoprotein (AFP), carcinoembryonic antigen (CEA), carbohydrate antigen (CA)125 and prostate special antigen (PSA), were used as model analytes. The resulting immunosensor could simultaneously detect four antigens in single-pass differential pulse voltammetry (DPV) scan, and exhibited obviously improved senstivity compared to previous similar immunosensors, displayed good linear relationships in the ranges from 0.2 to 800 pg/mL for AFP, 0.2 to 600 pg/mL for CEA, 0.2 to 1000 pg/mL for CA125, 0.2 to 800 pg/mL for PSA and with detection limits of 62, 48, 77 and 60 fg/mL, respectively.

Capillary electrophoresis-chemiluminescence detection for carcino-embryonic antigen based on aptamer/graphene oxide structure

A new strategy is proposed for determination of carcino-embryonic antigen (CEA) based on aptamer/graphene oxide (Apt/GO) by capillary electrophoresis-chemiluminescence (CE-CL) detection system. CEA aptamer conjugated with horseradish peroxidase (HRP) firstly mixes with GO, and the CL will be quenched because the stack of HRP-Apt on GO leads to chemiluminescence resonance energy transfer (CRET). When CEA exists, the specific combination of HRP-Apt and CEA can form HRP-Apt-CEA complex, which dissociates from GO. Then, the CL catalyzed by HRP-Apt-CEA complex can be detected without any CRET, and the content of CEA can be estimated by the CL intensity. It has been proved that the interference issue resulted from free HRP-Apt is solved well by mixing GO firstly with HRP-Apt, which blocks the free HRP-Apt's CL signal due to CL quenching effect of GO; and the interference resulted from GO to CL is also solved by CE, then the sensitivity and accuracy can be greatly improved. Results also showed that the CL intensity had a linear relationship with the concentration of CEA in the range from 0.0654 to 6.54 ng/mL, and the limit of detection was approximately 4.8 pg/mL (S/N = 3). This proposed method with high specificity offers a new way for separation and determination of biomolecule, and has good potential in application of biochemistry and bioanalysis.

Cerium oxide-deposited mesoporous silica nanoparticles for the determination of carcinoembryonic antigen in serum using inductively coupled plasma-mass spectrometry

CeO2-deposited mesoporous silica nanoparticles were synthesized as a probe to determine carcinoembryonic antigen (CEA) in serum by inductively coupled plasma-mass spectrometry (ICP-MS). The prepared mesoporous nanoparticles were modified and tagged to the target for sandwich-type immunoassay. Fe3O4 magnetic nanoparticles (MNPs) were also synthesized and immobilized with antibody to extract the target biomarker. The calibration curve of the synthesized CeO2-deposited silica nanoparticles, which was plotted by the signal ratio of (140)Ce/(57)Fe measured by ICP-MS vs. the concentration of CEA, showed excellent linearity and sensitivity owing to the signal amplification and low spectral interference. Under optimal conditions, the sandwich-type analytical method was applied to determine CEA in serum spiked in the range of 0.001-5 ng mL(-1) and showed a limit of detection of 0.36 ng mL(-1). Since the deposited CeO2 in the mesoporous silica layer can be substituted by other metal compounds, various kinds of metal-deposited nanoparticles can be prepared as probe materials for multiplex detection in bioanalysis.

An electrochemical immunosensor for ultrasensitive detection of carbohydrate antigen 199 based on Au@Cu(x)OS yolk-shell nanostructures with porous shells as labels

A novel and sensitive electrochemical immunosensor for ultrasensitive detection of pancreatic cancer biomarker carbohydrate antigen 199 (CA199) was proposed by using Au@Cu(x)OS yolk-shell nanostructures with porous shells as labels for signal amplification. Au@Cu(x)OS yolk-shell nanostructures exhibit high electrocatalytic activity toward the reduction of hydrogen peroxide (H2O2) as analytical signal. Moreover, secondary antibody (Ab2) can adsorb on the surface of Au@Cu(x)OS with porous shells which has large surface area and could greatly increase the probability of Ab2-antigen interactions thereby leading to higher sensitivity. Reduced graphene oxide-tetraethylene pentamine (rGO-TEPA), containing abundant amine groups, was supported Au nanoparticles as a support platform to immobilize the primary antibody (Ab1). The resulting sensing interface of rGO-TEPA/AuNPs could provide a large electroconductive surface area, allowing high loadings of the biological recognition elements as well as the occurrence of electrocatalytic and electron-transfer processes. Under optimal conditions, the immunosensor exhibited a wide linear response to CA199 ranging from 0.001 to 12 U/mL with a low detection limit of 0.0005 U/mL. The designed immunosensor displayed good precision, high sensitivity, acceptable stability and reproducibility, and has been applied to the analysis of serum with satisfactory results. The proposed method provides a new promising platform of clinical immunoassay for other biomolecules.

Ultrasensitive electrochemical immunosensors for multiplexed determination using mesoporous platinum nanoparticles as nonenzymatic labels

An ultrasensitive multiplexed immunoassay method was developed at a disposable immunosensor array using mesoporous platinum nanoparticles (M-Pt NPs) as nonenzymatic labels. M-Pt NPs were prepared by ultrasonic method and employed to label the secondary antibody (Ab2) for signal amplification. The immunosensor array was constructed by covalently immobilizing capture antibody (Ab1) on graphene modified screen printed carbon electrodes (SPECs). After the sandwich-type immunoreactions, the M-Pt-Ab2 was bound to immunosensor surface to catalyze the electro-reduction of H2O2 reaction, which produced detectable signals for readout of analytes. Using breast cancer related panel of tumor markers (CA125, CA153 and CEA) as model analytes, this method showed wide linear ranges of over 4 orders of magnitude with the detection limits of 0.002 U mL(-1), 0.001 U mL(-1) and 7.0 pg mL(-1) for CA125, CA153 and CEA, respectively. The disposable immunosensor array possessed excellent clinical value in cancer screening as well as convenient point of care diagnostics.

Multiplex detection of B-type natriuretic peptide, cardiac troponin I and C-reactive protein with photonic suspension array

A novel photonic suspension array has been developed for multiplex immunoassay. The carriers of this array were silica colloidal crystal beads (SCCBs). The codes of these carriers have characteristic reflection peaks originating from their structural periodicity; therefore they do not suffer from fading, bleaching, quenching or chemical instability. In addition, the fluorescence background of SCCBs is negligible because no fluorescence materials or dyes are involved. With a sandwich method, the proposed suspension array was used for simultaneous multiplex detection of heart failure (HF) and coronary heart disease (CAD) biomarkers in one test tube. The results showed that the three biomarkers: cardiac troponin I (cTnI), C-reactive protein (CRP) and B-type natriuretic peptide (BNP) could be assayed in the ranges of 0.1-500 ng/ml, 1-500 mg/L and 0.02-50 ng/ml with detection limits of 0.01 ng/ml, 0.36 mg/L and 0.004 ng/ml at 3σ, respectively. There were no significant differences between the photonic suspension array and traditional parallel single-analyte test. This novel method demonstrated acceptable accuracy, high detection sensitivity and reproducibility and excellent storage stability. This technique provides a new strategy for low cost, automated, and simultaneous multiplex immunoassays of bio-markers.

Paper-based chemiluminescence ELISA: lab-on-paper based on chitosan modified paper device and wax-screen-printing

A novel lab-on-paper device combining the simplicity and low-cost of microfluidic paper-based analytical devices (μPADs) and the sensitivity and selectivity of chemiluminescence ELISA (CL-ELISA) for the high-throughput, rapid, stable and reusable point-of-care testing is presented here. Chitosan was used to modify μPADs to covalently immobilize antibodies on μPADs. Thus, sandwich CL-ELISA on μPADs can be easily realized for further development of this technique in sensitive, specific and low-cost application. The paper device was fabricated by a low-cost, simple, and rapid wax-screen-printing method. Using tumor markers and paper microzone plate as model, the application test of this paper-based CL-ELISA was successfully performed with a linear range of 0.1-35.0 ng mL(-1) for α-fetoprotein, 0.5-80.0 U mL(-1) for cancer antigen 125 and 0.1-70.0 ng mL(-1) for carcinoembryonic antigen. Since the cutoff values of the three tumor markers in clinical diagnosis are 25 ng mL(-1), 35 U mL(-1) and 5 ng mL(-1), the sensitivity and linear ranges of the proposed method were enough for clinical application. In addition, this lab-on-paper immunodevice can provide reproducible results upon storage at 4 °C (sealed) for at least 5 weeks. Ultimately, this novel chitosan modification and wax-screen-printing methodology for μPADs can be readily translated to other signal reporting mechanism including electrochemiluminescence and photoelectrochemistry, and other receptors such as enzyme receptors and DNA receptors for determination of DNA, proteins and small molecules in point-of-care testing.