Sensitive Detection Of Prostate Specific Antigen Research Articles

All-solid-state metal-mediated Z-scheme photoelectrochemical immunoassay with enhanced photoexcited charge-separation for monitoring of prostate-specific antigen

An all-solid-state metal-mediated Z-scheme photoelectrochemical (PEC) immunoassay was designed for sensitive detection of prostate-specific antigen (PSA) by using WO3-Au-CdS nanocomposite as photoactive material and copper ion (Cu2+) as an inhibitor. The Z-scheme PEC system comprising of CdS nanoparticle (photosystem I; PS I), WO3 nanorod (photosystem II; PS II) and gold nanoparticle (Au NP; solid electron mediator) was reasonably established by a simple and green synthetic method. As an important part of Z-scheme system, the sandwiched gold nanoparticles between electron donor materials and hole provider materials could accelerate electron transfer from positive conduction band (CB) of WO3 to negative valence band (VB) of CdS, thus resulting in high-efficient separation of the carriers. In the presence of target PSA, a sandwiched immunoreaction was executed between capture antibody-coated microplate and CuO nanoparticle-labeled detection antibody. Thereafter, CuO nano labels were dissolved into Cu2+ ions under acidic condition to decrease the photocurrent of Z-scheme WO3-Au-CdS thanks to the formation of exciton trapping center of CuxS (x = 1,2) on the surface. Under optimum conditions, Z-scheme PEC immunoassay exhibited good photocurrents toward target PSA within a linear range of 0.01–50 ng mL−1 at a limit of detection of 1.8 pg mL−1. Moreover, the Z-scheme PEC immunoassay had high selectivity and accuracy. Importantly, this method provides a new horizon for detection of disease-related biomarkers with high sensitivity.

CdTe@SiO2 signal reporters-based fluorescent immunosensor for quantitative detection of prostate specific antigen

In this paper, an immunosensor using CdTe@SiO2 core-shell nanoparticles as labels was constructed for highly sensitive detection of prostate-specific antigen (PSA). In this approach, CdTe@SiO2 core-shell nanoparticles were synthesized using the sol-gel method. The additional Cd ions and sulfur source in SiO2 shell can greatly enhance the fluorescence intensity of CdTe nanocrystals. The reason is the formation of CdS-like cluster in SiO2 shell, which reduced the quantum size effect. The obtained CdTe@SiO2 nanoparticles also exhibited excellent biocompatibility, which was ideal for applying in biomarker detection. Furthermore, PSA capture antibodies functionalized magnetic Fe3O4 nanoparticles (Fe3O4-Ab1) were utilized in the proposed immunosensor to capture and enrich the PSA. The captured PSA was then immuno-recognized by CdTe@SiO2 labeled with PSA detection antibodies (CdTe@SiO2-Ab2) by forming the sandwich complex Fe3O4-Ab1/PSA/Ab2-CdTe@SiO2. The construction of this immunosensor was confirmed by fluorescence spectroscopy. The proposed immunosensor showed a good linear relationship between the fluorescent intensity and the target PSA concentration ranging from 0.01 to 5 ng/mL, and a detection limit as low as 0.003 ng/mL was achieved. The sensor also exhibited good specificity to PSA. This highly sensitive and specific immunosensor has great potential to be used in other biological detection.

A novel electrochemical immunosensor for highly sensitive detection of prostate-specific antigen using 3D open-structured PtCu nanoframes for signal amplification

Herein, a novel electrochemical ultrasensitive immunosensor was designed for detecting prostate-specific antigen (PSA) with three-dimensional (3D) PtCu hollow nanoframes (PtCu HNFs) as signal amplification. The highly opened PtCu HNFs were synthesized by a one-pot solvothermal method with cetyltrimethylammonium chloride (CTAC) and trishydroxymethyl aminomethane (Tris) as co-structuring directors. The architectures enlarged the loading of prostate specific antibodies (Ab) and efficiently catalyzed hydrogen peroxide (H2O2) reaction, ultimately amplifying the signals. And polylysine was used to disperse PtCu HNFs, improve the biocompatibility and bind the Ab on the electrode surface. The fabricated immunosensor exhibited lower detection limit (0.003 ng mL–1, S/N = 3), and wider linear range (0.01–100.0 ng mL–1), along with the improved reproducibility, selectivity and stability for the assay of PSA. Thus, it is a desirable platform for PSA detection in clinical diagnosis and practical applications.

Formation of Homogeneous Epinephrine-Melanin Solutions to Fabricate Electrodes for Enhanced Photoelectrochemical Biosensing.

The development of a simple but effective surface modification method is very important for the construction of biosensing interfaces. In this work, a postsynthetic water-soluble epinephrine-melanin (EPM) prepared from the self-polymerization of epinephrine has been demonstrated as an alternative of the widely used in situ formed polydopamine (PDA) for the surface coating of TiO2 nanoparticles and the construction of a photoelectrochemical (PEC) biosensing interface. In contrast to the formation of insoluble aggregates in solution for dopamine, a homogeneous solution was obtained for epinephrine after the self-polymerization. The use of EPM as a postsynthetic material enables the surface coating of TiO2 with the simple drop-casting method. Compared with the widely used dip-coating method for in situ PDA modification, the developed drop-casting method based on the use of water-soluble postsynthetic EPM saves more time, avoids the waste of bulk solution, and undoubtedly decreases the batch-to-batch inconsistencies. The simple coating of commercially available TiO2 nanoparticles with EPM greatly enhances the PEC performance due to the charge transfer property of EPM. The application of EPM in the construction of the PEC biosensing interface was demonstrated by the immobilization of a model biorecognition element (prostate specific antigen (PSA) antibody) onto EPM modified indium tin oxide (ITO) photoanode. Sensitive detection of PSA with high selectivity and stability was obtained on the basis of the biological recognition ability of PSA antibody. This work may renew the use of postsynthetic melanin-like biopolymers in other fields.

A comparative Study of Aptasensor Vs Immunosensor for Label-Free PSA Cancer Detection on GQDs-AuNRs Modified Screen-Printed Electrodes

Label-free and sensitive detection of PSA (Prostate Specific Antigen) is still a big challenge in the arena of prostate cancer diagnosis in males. We present a comparative study for label-free PSA aptasensor and PSA immunosensor for the PSA-specific monoclonal antibody, based on graphene quantum dots-gold nanorods (GQDs-AuNRs) modified screen-printed electrodes. GQDs-AuNRs composite has been synthesized and used as an electro-active material, which shows fast electron transfer and catalytic property. Aptamer or anti-PSA has immobilized onto the surface of modified screen printed electrodes. Three techniques are used simultaneously, viz. cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedence spectroscopy (EIS) to investigate the analytical performance of both PSA aptasensor and PSA immunosensor with its corresponding PSA antigen. Under optimum conditions, both sensors show comparable results with an almost same limit of detection (LOD) of 0.14 ng mL−1. The results developed with aptasensor and anti-PSA is also checked through the detection of PSA in real samples with acceptable results. Our study suggests some advantages of aptasensor in terms of better stability, simplicity and cost effectiveness. Further our present work shows enormous potential of our developed sensors for real application using voltammetric and EIS techniques simultaneous to get reliable detection of the disease.

Visual electrochemiluminescence ratiometry on bipolar electrode for bioanalysis

In this work, we developed a visual ECL ratiometry on a closed bipolar electrode (BPE) for the detection of prostate specific antigen (PSA), prostate cancer biomarker. High efficient CdTe QDs was synthesized which emitted visualized red light at BPE cathode. Integrating with the anodic ECL emitters, luminol, visual emission of red-blue ratiometric ECL was achieved in BPE array chips. As a sensing probe, Au NRs nanocomposite was assembled on the surface of the cathode and acted as both the quencher of the CdTe QDs ECL and the promoter of the luminol ECL. After incubated with PSA, the Au NRs nanocomposite was peeled off from the electrode surface due to the specific recognition between PSA and aptamer. Consequently, the cathode ECL partly recovered and the anode ECL turned off. By measuring the ratio of visual ECL intensity at two poles of BPE, sensitive detection of PSA was achieved with a linear range from 1.0ng/mL to 1.0μg/mL and detection limit of 0.5ng/mL (S/N=3). This strategy combining the BPE-ECL and visual ratiometry provided an accurate and intrinsic way for the sensing of PSA and showed good perspective in the clinical diagnosis.

A novel peptide/Fe3O4@SiO2-Au nanocomposite-based fluorescence biosensor for the highly selective and sensitive detection of prostate-specific antigen

Highly selective and sensitive detection methods are very important for the early diagnosis of prostate-specific antigen (PSA). Here, we present a novel peptide/Fe3O4@SiO2-Au nanocomposite-based fluorescence biosensor for highly selective and sensitive detection of PSA. The biosensor was made by self-organizing 5-FAM labeled peptides onto the surface of magnetic Fe3O4@SiO2-Au nanocomposites (MNCPs), resulting in efficient quenching of the FAM fluorescence. The PSA specifically recognized and cleaved the 5-FAM-labeled peptides, leading to the fluorescence recovery. This is the first report of the MNCPs by in situ growth of Au nanoparticles (AuNPs) on the SiO2 encapsulated single Fe3O4 nanocubes. The MNCPs feature robust salt stability, and allow for effective fluorescence quenching and easy magnetic separation, which greatly decrease the background fluorescence. The peptide/MNCPs-based fluorescence biosensor measure a wide range of concentrations of PSA, from 1.0 × 10−12 to 1.0 × 10−9g/mL, with a limit of detection (LOD) of 3.0 × 10−13g/mL in both standard solutions and serum samples, demonstrating the great potential of this biosensor platform for use in clinical and biological assays.

Reduced graphene oxide/BiFeO3 nanohybrids-based signal-on photoelectrochemical sensing system for prostate-specific antigen detection coupling with magnetic microfluidic device

A novel magnetic controlled photoelectrochemical (PEC) sensing system was designed for sensitive detection of prostate-specific antigen (PSA) using reduced graphene oxide-functionalized BiFeO3 (rGO-BiFeO3) as the photoactive material and target-triggered hybridization chain reaction (HCR) for signal amplification. Remarkably enhanced PEC performance could be obtained by using rGO-BiFeO3 as the photoelectrode material due to its accelerated charge transfer and improved the visible light absorption. Additionally, efficient and simple operation could be achieved by introducing magnetic controlled flow-through device. The assay mainly involved in anchor DNA-conjugated magnetic bead (MB-aDNA), PSA aptamer/trigger DNA (Apt-tDNA) and two glucose oxidase-labeled hairpins (H1-GOx and H2-GOx). Upon addition of target PSA, the analyte initially reacted with the aptamer to release the trigger DNA, which partially hybridized with the anchor DNA on the MB. Thereafter, the unpaired trigger DNA on the MB opened the hairpin DNA structures in sequence and propagated a chain reaction of hybridization events between two alternating hairpins to form a long nicked double-helix with numerous GOx enzymes on it. Subsequently, the enzymatic product (H2O2) generated and consumed the photo-excited electrons from rGO-BiFeO3 under visible light irradiation to enhance the photocurrent. Under optimal conditions, the magnetic controlled PEC sensing system exhibited good photocurrent responses toward target PSA within the linear range of 0.001 − 100ng/mL with a detection limit of 0.31pg/mL. Moreover, favorable selectivity, good stability and satisfactory accuracy were obtained. The excellent analytical performance suggested that the rGO-BiFeO3-based PEC sensing platform could be a promising tool for sensitive, efficient and low cost detection of PSA in disease diagnostics.

Bio-bar-code-based photoelectrochemical immunoassay for sensitive detection of prostate-specific antigen using rolling circle amplification and enzymatic biocatalytic precipitation

Methods based on photoelectrochemistry have been developed for immunoassay, but most involve in a low sensitivity and a relatively narrow detectable range. Herein a new bio-bar-code-based split-type photoelectrochemical (PEC) immunoassay was designed for sensitive detection of prostate-specific antigen (PSA), coupling rolling circle amplification (RCA) with enzymatic biocatalytic precipitation. The bio-bar-code-based immunoreaction was carried out on monoclonal anti-PSA antibody (mAb1)-coated microplate using primer DNA and polyclonal anti-PSA antibody-conjugated gold nanoparticle (pDNA-AuNP-pAb2) with a sandwich-type assay format. Accompanying the immunocomplex, the labeled primer DNA on gold nanoparticle readily triggered RCA reaction in the presence of padlock probe/dNTPs/ligase/polymerase. The RCA product with a long single-stranded DNA could cause the formation of numerous hemin/G-quadruplex-based DNAzyme concatamers. With the assistance of nicking endonuclease, DNAzyme concatamers were dissociated from gold nanoparticle, which catalyzed the precipitation of 4-chloro-1-naphthol in the presence of H2O2 onto CdS nanorods-coated electrode (as the photoanode for the generated holes). The formed insoluble precipitate inhibited the electron transfer from the solution to CdS nanorods-modified electrode by using ascorbic acid as the electron donor. Under the optimum conditions, the photocurrent of the modified electrode decreased with the increasing of PSA concentration. A detectable concentration for target PSA with this system could be achieved as low as 1.8pgmL−1. In addition, our strategy also showed good reproducibility, high specificity and accuracy matched well with commercial PSA ELISA kits for real sample analysis. These remarkable properties revealed that the developed PEC immunoassay has great potential as a useful tool for the detection of PSA in practical application.

Reduced graphene oxide-functionalized FeOOH for signal-on photoelectrochemical sensing of prostate-specific antigen with bioresponsive controlled release system

A new and signal-on photoelectrochemical (PEC) sensing platform was successfully designed for the sensitive detection of prostate-specific antigen (PSA), using reduced graphene oxide- functionalized iron oxyhydroxide (FeOOH-rGO) as the photoactive material, accompanying target-responsive controlled release system to achieve the signal amplification. Introduction of rGO as electron mediator greatly facilitated the electron transfer from FeOOH to electrode under visible light, which inhibited the electron-hole recombination to enhance the photo-activity of FeOOH-rGO. Additionally, the bioresponsive release system was controlled via the reaction of target PSA with the aptamer capped glucose-loading mesoporous silica nanoparticle (MSN) to release numerous glucose molecules (as the electron donors) for the amplification of the photocurrent generated from FeOOH-rGO. Thus, more glucose molecules could be released and enhanced photocurrents could be obtained with the increasing PSA concentrations. Experimental results showed that the photocurrents of the PEC sensing platform were linearly dependent on the logarithm of PSA concentrations from 1.0pg/mL to 100ng/mL. Moreover, the PEC sensing system afforded good stability and specificity, and its accuracy matched well with the commercial PSA enzyme-linked immunosorbent assay (ELISA) kit. The excellent performance of the PEC sensing platform indicated its promising prospect as a useful tool for PSA detection in practical application.

Using reduced graphene oxide-Ca:CdSe nanocomposite to enhance photoelectrochemical activity of gold nanoparticles functionalized tungsten oxide for highly sensitive prostate specific antigen detection

An ultrasensitive sandwich-type photoelectrochemical (PEC) immunosensor was constructed for the detection of prostate specific antigen (PSA). In this work, Au-nanoparticle-loaded tungsten oxide (WO3-Au) hybrid composites was applied as PEC sensing platform, while Ca ions doped CdSe equipped on the conducting framework of reduced graphene oxide (rGO-Ca:CdSe) nanocomposites were employed as the signal amplification probe. As for WO3-Au, massive Au nanoparticles were formed on the surface of WO3 without any additional reducing agent, providing a novel nanocarriers for anchoring plenty of the primary antibodies due to the large specific surface area and good biocompatibility by chemical bonding between Au nanoparticles and -NH2 of antibodies. Besides, the incorporation of the rGO and the doping of Ca ions could improve the conductivity and hinder the recombination of electron-hole pairs of CdSe nanoparticles effectively, thereby enhancing the photocurrent conversion efficiency. Based on the sandwich immunoreaction, the primary antibody was immobilized onto WO3-Au substrate, after the formed rGO-Ca:CdSe labels were captured onto the electrode surface via the specific antibody-antigen interaction, the photocurrent intensity could be further enhanced due to the sensitization effect. Under the optimal conditions, the proposed PEC immunosensor shows a linear relationship between photocurrent variation and the logarithm of PSA concentration in the wide range of 5pgmL−1 to 50ngmL−1 with a low detection limit of 2.6pgmL−1 (S/N=3). Moreover, it also presented good stability and acceptable specificity, indicating the potential applications in clinical diagnostics.

A novel immunosensing platform for highly sensitive prostate specific antigen detection based on dual-quenching of photocurrent from CdSe sensitized TiO2 electrode by gold nanoparticles decorated polydopamine nanospheres

Herein, a novel photoelectrochemical (PEC) immunosensing platform for highly sensitive detection of prostate specific antigen (PSA) was constructed based on dual-quenching of photocurrent from CdSe sensitized TiO2 electrode by gold nanoparticles decorated dopamine–melanin nanospheres (AuNPs-Dpa-melanin CNSs). In this proposal, CdSe sensitized TiO2 was used as photoelectrochemical matrix and the functional AuNPs-Dpa-melanin CNSs were used as signal quenching element. The dual quenching of the gold nanoparticles decorated Dpa-melanin CNSs to the CdSe sensitized TiO2 was achieved as follows: (i) the strong energy transfer between the CdSe quantum dots (QDs) and Au NPs diminishes the photocurrent signal of CdSe QDs; (ii) the steric hindrance of AuNPs-Dpa-melanin CNSs partly obstructs the diffusion of the electron donor, i.e. ascorbic acid, to the surface of photoelectrode, which make the depleting efficiency of the photogenerated holes decrease, leading to a declined photocurrent intensity. On the basis of the dual quenching effect of AuNPs-Dpa-melanin CNSs, a competitive immunosensing platform for PSA was designed upon the specific binding of anti-PSA to PSA and PSA functionalized AuNPs-Dpa-melanin CNSs conjugates. This proposed immunosensor possesses wide linear range from 1.0×10–11gmL−1 to 1.0×10−7gmL−1 with the detection limit of 2.7pgmL−1. Moreover, the applicability of the present method was demonstrated in the determination of PSA in human serum. The strategy creates new paradigms for PSA and other tumor markers detection and demonstrates high sensitivity, good specificity, and satisfied applicability in complex biological samples.

Nanogold-functionalized g-C3N4 nanohybrids for sensitive impedimetric immunoassay of prostate-specific antigen using enzymatic biocatalytic precipitation

This work reports on a new impedimetric immunosensing strategy for sensitive detection of prostate-specific antigen (PSA) in biological fluids. The assay was carried out on monoclonal anti-PSA capture antibody-modified glassy carbon electrode with a sandwich-type detection format. Gold nanoparticles-decorated g-C3N4 nanosheets (AuNP/g-C3N4), synthesized by the wet-chemistry method, were utilized for the labeling of polyclonal anti-PSA detection antibody and horseradish peroxidase (HRP). Upon target PSA introduction, the sandwiched immunocomplex could be formed between capture antibody and detection antibody. Followed by the AuNP/g-C3N4, the labeled HRP could catalyze 4-choloro-1-naphthol into benzo-4-chlorohexadienone. The as-generated insoluble product was coated on the electrode surface, thus increasing the Faradaic impedance of Fe(CN)64−/3− indicator between the solution and the base electrode. Under the optimal conditions, the impedance increased with the increasing target PSA in the sample, and exhibited a wide linear range from 10pgmL−1 and 30ngmL−1 with a detection limit of 5.2pgmL−1. A repeatability and intermediate precision of <14% was accomplished. The specificity and method accuracy in comparison with commercial PSA ELISA kit for analysis of human serum specimens were relatively satisfactory.

Visible-light driven biofuel cell based on hierarchically branched titanium dioxide nanorods photoanode for tumor marker detection

In this work, a novel sensing platform based on visible light driven biofuel cell (BFC) has been facilely designed for sensitive detection of prostate-specific antigen (PSA) with the photo-response bioanode, realizing the dual route energy conversion of light energy and chemical energy to electricity. The hierarchical branched TiO2 nanorods (B-TiO2 NRs) decorated with CdS quantum dots (QDs) act as the substrate to confine glucose dehydrogenase (GDH) for the visible light driven glucose oxidation at the bioanode. Three dimensional flowers like hierarchical carbon/gold nanoparticles/bilirubin oxidase (3D FCM/AuNPs/BOD) bioconjugate served as biocatalyst for O2 reduction at the biocathode. With an increase in the concentration of PSA, the amount of BOD labels on biocathode increases, thus leading to the higher current output of the as-proposed visible light driven BFC. Based on this, this sensing platform provide great performance in sensitivity and specificity, increasing linear detection range from 0.3pgmL−1 to 7μgmL−1 with a detection limit of 0.1pgmL−1. Most importantly, our new sensing strategy provided a simple and inexpensive sensing platform for tumor markers detection, suggesting its wide potential applications for clinical diagnostics.

Sensitivity improvement of a sandwich-type ELISA immunosensor for the detection of different prostate-specific antigen isoforms in human serum using electrochemical impedance spectroscopy and an ordered and hierarchically organized interfacial supramolecular architecture

A gold millielectrode (GME) functionalized with a mixed (16-MHA + EG3SH) self-assembled monolayer (SAM) was used to fabricate an indirect enzyme-linked immunosorbent assay (ELISA) immunosensor for the sensitive detection of prostate-specific antigen (PSA), a prostate cancer (PCa) biomarker, in human serum samples. To address and minimize the issue of non-specific protein adsorption, an organic matrix (amine-PEG3-biotin/avidin) was assembled on the previously functionalized electrode surface to build up an ordered and hierarchically organized interfacial supramolecular architecture: Au/16-MHA/EG3SH/amine-PEG3-biotin/avidin. The electrode was then exposed to serum samples at different concentrations of a sandwich-type immunocomplex molecule (BtnAb-AgPSA-HRPAb), and its interfacial properties were characterized using electrochemical impedance spectroscopy (EIS). Calibration curves for polarization resistance (RP) and capacitance (1/C) vs. total and free PSA concentrations were obtained and their analytical quality parameters were determined. This approach was compared with results obtained from a commercially available ELISA immunosensor. The results obtained in this work showed that the proposed immunosensor can be successfully applied to analyze serum samples of patients representative of the Mexican population.

Silver nanoprism etching-based plasmonic ELISA for the high sensitive detection of prostate-specific antigen.

Ultrasensitive and quantitative detection using simple and low-cost assays is critical in clinical diagnostics. In this report, we developed a triangular silver nanoprism (AgNPRs) etching-based plasmonic biosensor for the detection of cancer biomarkers. The triangular AgNPRs-based plasmonic biosensor is an enzyme-linked immunosorbent assay combined with the enzyme-mediated surface plasmon resonance (SPR) of triangular AgNPRs. Triangular AgNPRs uses the immune response of prostate-specific antigen (PSA) to trigger the glucose oxidase (GOx)-catalysed oxidation of glucose (Glu), producing hydrogen peroxide. Hydrogen peroxide acts as an oxidant to etch the triangular AgNPRs into smaller spherical silver nanoparticles, which is accompanied by a substantial blueshift of the SPR peak and a colourimetric blue-to-purple change that can be observed by the naked eye. The SPR peak shift enables the quantitative assessment of PSA due to the remarkable colour change. The triangular AgNPRs-based plasmonic ELISA approach exhibited a quasilinear response to logarithmic PSA concentrations in the range of 10fg/mL to 100pg/mL with a limit of detection (LOD) of 4.1fg/mL. In addition, the LOD of PSA in this approach exceeds that of the conventional HRP-based ELISA (1.25ng/mL) approach by more than 5 orders of magnitude. Patient serum samples from 16 donors were assayed with triangular AgNPRs-based plasmonic ELISA. The results from the triangular AgNPRs-based immunoassay and the time-resolved fluorescence immunoassay showed excellent correlation, and there were no significant differences in the quantified amounts of PSA. The triangular AgNPRs-based plasmonic ELISA approach has advantages (ultrasensitive, cost-effective, ease of operation) that are expected to be of great interest in diagnostics and to be suitable for a point-of-care test.

Target protein induced cleavage of a specific peptide for prostate-specific antigen detection with positively charged gold nanoparticles as signal enhancer.

In this work, a new "signal-on" electrochemical biosensor for sensitive detection of prostate-specific antigen (PSA) was developed on the basis of target protein induced cleavage of a specific peptide with positively charged gold nanoparticles (AuNPs) as signal enhancer.

Novel rolling circle amplification and DNA origami-based DNA belt-involved signal amplification assay for highly sensitive detection of prostate-specific antigen (PSA).

Prostate-specific antigen (PSA) is one of the most important biomarkers for the early diagnosis and prognosis of prostate cancer. Although many efforts have been made to achieve significant progress for the detection of PSA, challenges including relative low sensitivity, complicated operation, sophisticated instruments, and high cost remain unsolved. Here, we have developed a strategy combining rolling circle amplification (RCA)-based DNA belts and magnetic bead-based enzyme-linked immunosorbent assay (ELISA) for the highly sensitive and specific detection of PSA. At first, a 96-base circular DNA template was designed and prepared for the following RCA. Single stranded DNA (ssDNA) products from RCA were used as scaffold strand for DNA origami, which was hybridized with three staple strands of DNA. The resulting DNA belts were conjugated with multiple enzymes for signal amplification and then employed to magnetic bead based ELISA for PSA detection. Through our strategy, as low as 50 aM of PSA can be detected with excellent specificity.

Nanoparticles for Enhanced Sensitivity in Electrochemical Immunoassays

In this manuscript, we report on electrochemical biosensors based on various nanoparticles (NPs) as labels for sensitive detection of protein biomarkers. We used silica nanoparticle as a carrier to loading a large amount of electroactive species such as poly(guanine) for sensitive immunoassay of tumor necrosis factor-alpha (TNF-α). We took the advantages of the unique hollow structure and reconstruction properties of apoferritin to prepare Cd3(PO4)2 nanoparticles as labels for sensitive assay of TNF-α. A novel immunochromatographic/electro-chemical biosensor based on quantum dots as labels has also been developed for rapid and sensitive detection of prostate-specific antigen (PSA) in human serum. These biosensors are quite sensitive with the detection limit at pM level and these approaches based on nanoparticle labels offer a new avenue for sensitive detection of protein biomarkers.

A nanoparticle label/immunochromatographic electrochemical biosensor for rapid and sensitive detection of prostate-specific antigen

We present a nanoparticle (NP) label/immunochromatographic electrochemical biosensor (IEB) for rapid and sensitive detection of prostate-specific antigen (PSA) in human serum. This IEB integrates the immunochromatographic strip with the electrochemical detector for transducing quantitative signals. The NP label, made of CdSe@ZnS, serves as a signal-amplifier vehicle. A sandwich immunoreaction was performed on the immunochromatographic strip. The captured NP labels in the test zone were determined by highly sensitive stripping voltammetric measurement of the dissolved metallic component (cadmium) with a disposable-screen-printed electrode, which is embedded underneath the membrane of the test zone. Several experimental parameters (e.g., immunoreaction time, the amount of anti-PSA-NP conjugations applied) and electrochemical detection conditions (e.g., preconcentration potential and time) were optimized using this biosensor for PSA detection. The analytical performance of this biosensor was evaluated with serum PSA samples according to the “figure-of-merits” (e.g., dynamic range, reproducibility, and detection limit). The results were validated with enzyme-linked immunosorbent assay (ELISA) and showed high consistency. It is found that this biosensor is very sensitive with the detection limit of 0.02 ng mL −1 PSA and is quite reproducible (with a relative standard deviation (R.S.D.) of 6.4%). This method is rapid, clinically practical, and less expensive than other diagnostic tools for PSA; therefore, this IEB coupled with a portable electrochemical analyzer shows great promise for simple, sensitive, quantitative point-of-care testing of disease-related protein biomarkers.