Magnetic-particle-based, ultrasensitive chemiluminescence enzyme immunoassay for free prostate-specific antigen

Dual chemical bonding construction of electrochemical peptide sensor based on GDY/MOFs(Fe) composite for ultra-low determination of prostate-specific antigen

A novel "double chemical bonding" electrochemical peptide biosensor 2FcP-GA-GDY(Fe)@NMIL-B was developed for highly selective, ultrasensitive, and ultrastable identification of prostate-specific antigen (PSA). The C-Fe-O chemical bond linking Fe-Graphdiyne (Fe-GDY) with NH2-MIL88B(Fe) (NMIL88B) as the first chemical bonding of electrode carrier Fe-GDY@NH2-MIL88B(Fe) (GDY(Fe)@NMIL) significantly accelerates electron transport. With glutaraldehyde (GA) as a crosslinking agent, the Schiff-base -NC- formed by GDY(Fe)@NMIL nanocomposites links the two Fc molecules labeled peptides (2FcP) as the second chemical bonding, facilitating high-density attachment of peptides to the electrode carrier in a firm manner. When the PSA analyte is introduced to identify and cleave the specific peptide, the release of ferrocene from its head leads to a decrease in the electrical signal, enabling sensitive detection. The prepared sensing platform exhibits exceptional analytical performance for PSA with an extended linear response range from 10 fg mL-1 to 50 ng mL-1. Additionally, the detection limit has been significantly reduced to an ultra-low level of only 0.94 fg mL-1, surpassing those reported in most literature by several orders of magnitude. Moreover, the 2FcP-GA-GDY(Fe)@NMIL-B sensor has excellent selectivity and stability while also showcasing great potential for practical application of PSA detection in human serum using the standard addition method.

Point-of-Care Prostate Specific Antigen Testing: Examining Translational Progress toward Clinical Implementation

Prostate cancer (PCa) is the second most common male cancer and is attributable to over 375,000 deaths annually. Prostate specific antigen (PSA) is a key biomarker for PCa and therefore measuring patient PSA levels is an important aspect of the diagnostic pathway. Automated immunoassays are currently utilized for PSA analysis, but they require a laboratory setting with specialized equipment and trained personnel. This results in high diagnostic costs, extended therapeutic turnaround times, and restrictions on testing capabilities in resource-limited settings. Consequently, there is a strong drive to develop point-of-care (PoC) PSA tests that can offer accurate, low-cost, and rapid results at the time and place of the patient. However, many emerging PoC tests experience a trade-off between accuracy, affordability, and accessibility which distinctly limits their translational potential. This review comprehensively assesses the translational advantages and limitations of emerging laboratory-level and commercial PoC tests for PSA determination. Electrochemical and optical PSA sensors from 2013 to 2023 are systematically examined. Furthermore, we suggest how the translational potential of emerging tests can be optimized to achieve clinical implementation and thus improve PCa diagnosis globally.

Overview on the Development of Alkaline-Phosphatase-Linked Optical Immunoassays

The drive to achieve ultrasensitive target detection with exceptional efficiency and accuracy requires the advancement of immunoassays. Optical immunoassays have demonstrated significant potential in clinical diagnosis, food safety, environmental protection, and other fields. Through the innovative and feasible combination of enzyme catalysis and optical immunoassays, notable progress has been made in enhancing analytical performances. Among the kinds of reporter enzymes, alkaline phosphatase (ALP) stands out due to its high catalytic activity, elevated turnover number, and broad substrate specificity, rendering it an excellent candidate for the development of various immunoassays. This review provides a systematic evaluation of the advancements in optical immunoassays by employing ALP as the signal label, encompassing fluorescence, colorimetry, chemiluminescence, and surface-enhanced Raman scattering. Particular emphasis is placed on the fundamental signal amplification strategies employed in ALP-linked immunoassays. Furthermore, this work briefly discusses the proposed solutions and challenges that need to be addressed to further enhance the performances of ALP-linked immunoassays.

Comparison of performance and clinical utility of different methods for detecting anti-PLA2R antibody

OBJECTIVES

This study aimed to compare the performance of enzyme-linked immunosorbent assay (ELISA) and magnetic particle chemiluminescence immunoassay (MP-CLIA) for detecting anti-phospholipase A2 receptor (PLA2R) antibody and their clinical significance in idiopathic membranous nephropathy (IMN) patients.

METHODS

Serum samples from 448 patients with different types of nephropathy, including 222 with IMN, were tested using both methods. Sensitivity, specificity, and prognostic significance of PLA2R antibody levels were evaluated.

RESULTS

Similar sensitivity and specificity of ELISA and MP-CLIA in identifying IMN patients was found. However, MP-CLIA performed better than ELISA in predicting the prognosis of IMN patients. Adjusting the cutoff value reduced the false-negative rate in both methods. Logistic regression analysis identified six variables, including MP-CLIA-PLA2R levels, eGFR, lymphocyte count, B lymphocyte count, NK cell count, and complement 4, as predictors of renal function outcomes in IMN patients.

CONCLUSIONS

Both ELISA and MP-CLIA are reliable methods for detecting anti-PLA2R antibodies in IMN patients. However, MP-CLIA is more accurate in predicting the prognosis of IMN. Combining MP-CLIA-PLA2R with other variables can help predict renal function outcomes in IMN patients. Our study emphasizes the importance of considering both analytical performance and clinical utility when selecting a PLA2R antibody assay kit.

A novel carboxyl polymer-modified upconversion luminescent nanoprobe for detection of prostate-specific antigen in the clinical gray zonebase by flow immunoassay strip

Prostate specific antigen (PSA) is a widely-used biomarker for the diagnosis, screening, and prognosis of prostate cancer (PCa). It is critical to develop a rapid and convenient method to accurately detect PSA levels, especially when the PSA levels are in the clinical gray area of 4-10 ng/mL. We developed a novel upconversion nanoparticle (UCNP)-based fluorescence lateral flow test strip for qualitatively and quantitatively detecting PSA. The carboxyl group-modified UCNPs (UCNP-COOH) were labeled with anti-PSA antibodies via 1-ethyl-3-(3-(dimethylamino)propyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) as labeling probes to recognize PSA. The fluorescence intensity of the UCNP-probe was then measured with a laser fluorescence scanner. A total of 1397 serum and 20 fingertip blood samples were collected to validate the UCNP strip. A reliable correlation between the area ratio (TC), reflecting the fluorescence intensity of the test/control line, and the PSA concentration was observed (r = 0.9986). The dose-dependent luminescence enhancement showed good linearity in the PSA concentration range from 0.1 to 100.0 ng/mL with a detection limit of 0.1 ng/mL. Our UCNP POCT strip demonstrated excellent accuracy, anti-interference and stability in the gray zone (4-10 ng/mL) of PSA clinical application and outperformed other PSA test strips. The UCNP strip showed good consistency with the Roche chemiluminescence assay in 1397 serum samples. It also showed good performance for PSA detection using fingertip blood samples. This novel UCNP-based test strip could be a sensitive and reliable POCT assay to detect PSA, facilitating the diagnosis and surveillance of PCa.

Detection of Carbohydrate Antigen 50 Based on a Novel Miniaturized Chemiluminescence Analyzer Enables Large-Scale Cancer Early Screening in Grassroots Community

Early screening of cancer can effectively prolong survival time and reduce cancer mortality. However, the existing health-monitoring devices can only be carried out in professional laboratories, so large-scale early cancer screening in resource-limited settings is hardly achieved. To embrace the challenge, we developed a novel chemiluminescence immunoassay (CLIA) analyzer that does not require a professional operation. Then, it was applied to detect carbohydrate antigen 50 (CA50), a non–organ-specific tumor marker for screening various cancers. As a result, the analyzer exhibited excellent performance that the total assay time was only 15 min, and the detection limit reached 0.057 U ml⁻¹. A coefficient of variance (CV) less than 15% was well-controlled for both intra- and inter-assay precision, and the linear range was 0–500 U ml⁻¹. More importantly, this analyzer can continuously detect 60 samples per hour without any professional paramedic. Finally, this analyzer has been applied to evaluate clinical samples and the detected results showed a good correlation with the clinical test results (correlation coefficient, 0.9958). These characteristics exactly meet large-scale and high-throughput early screening of cancer. Thus, this miniaturized analyzer for CA50 detection is promising to achieve early large-scale screening of cancer in the resource-limited grassroots community.

An Automated and Highly Sensitive Chemiluminescence Immunoassay for Diagnosing Mushroom Poisoning

Mushrooms containing Amanita peptide toxins are the major cause of mushroom poisoning, and lead to approximately 90% of deaths. Phallotoxins are the fastest toxin causing poisoning among Amanita peptide toxins. Thus, it is imperative to construct a highly sensitive quantification method for the rapid diagnosis of mushroom poisoning. In this study, we established a highly sensitive and automated magnetic bead (MB)-based chemiluminescence immunoassay (CLIA) for the early, rapid diagnosis of mushroom poisoning. The limits of detection (LODs) for phallotoxins were 0.010 ng/ml in human serum and 0.009 ng/ml in human urine. Recoveries ranged from 81.6 to 95.6% with a coefficient of variation <12.9%. Analysis of Amanita phalloides samples by the automated MB-based CLIA was in accordance with that of HPLC-MS/MS. The advantages the MB-based CLIA, high sensitivity, repeatability, and stability, were due to the use of MBs as immune carriers, chemiluminescence as a detection signal, and an integrated device to automate the whole process. Therefore, the proposed automated MB-based CLIA is a promising option for the early and rapid clinical diagnosis of mushroom poisoning.

Proximity binding induced nucleic acid cascade amplification strategy for ultrasensitive homogeneous detection of PSA

In this work, based on the powerful cycle amplification cascades of proximity hybridization-induced hybridization chain reaction and catalyzed hairpin assembly, we engineered a nonenzymatic and ultrasensitive method which combined the Mg²⁺-DNAzyme recycling signal amplification for the analysis of the human prostate specific antigen. Herein, we adopted PSA-conjugates as triggers in the self-assembly process of two hairpin DNAs (H1, H2) into the products of the CHA which could activate the HCR to induce repeated hybridization. And both ends of each adjacent sequence of the HCR products could form a unit of Mg²⁺-DNAzyme which in presence of cofactor Mg²⁺ could recognize and cyclically cleave the hairpin probes in the solution and thus generate observably enhanced fluorescent signal. Benefit from the nucleic acid circuit amplification strategy, PSA of concentration low to 0.73 pg mL^-1 was detected in this system. This homogeneous sensing method in solution avoid the use of the sophisticated equipment and complex operation, as well as addition of artificial enzyme, thus greatly reducing the constraints and complexity of experimental conditions. Moreover, considering most protein biomarkers in serum don't have their corresponding aptamers, this sensing method provide a general sensing approach for homogeneous sensitive detection of these important protein biomarkers which transfer rough antigen-antibody interactivity to smart signal amplification sensing strategies, thus exhibiting a remarkable prospect in clinical application.

Directional immobilization of antibody onto magnetic nanoparticles by Fc-binding protein-assisted photo-conjugation for high sensitivity detection of antigen

Immobilized antibodies with site-specific, oriented, and covalent pattern are of great significance to improve the sensitivity of solid-phase immunoassay. Here, we developed a novel antibody conjugation strategy that can immobilize antibodies in a directional and covalent manner. In this study, an IgG-Fc binding protein (Z domain) carrying a site-specific photo-crosslinker, p-benzoyl-L-phenylalanine, and a single C-terminal cysteine (Cys) handle was genetically engineered. Upon UV irradiation, the chimeric protein enables the Cys handle to couple with the native antibody in Fc-specific and covalent conjugation pattern, resulting in a novel thiolated antibody. Thus, an approach for the covalent, directional immobilization of antibodies to maleimide-modified magnetic nanoparticles (MNPs) was developed on the basis of the crosslinking between sulfhydryl and maleimide groups. The antibody-conjugated MNPs were applied in MNP-based enzyme-linked immunosorbent assay (ELISA) for the detection of carcinoembryonic antigen. The MNP-based ELISA presented a quantification linear range of 0.1-100 ng mL^-1 and detection limit of 0.02 ng mL^-1, which was approximately 100 times more sensitive than the traditional microplate ELISA (2.0 ng mL^-1). Thus, the proposed antibody immobilization approach can be used in surface functionalization for the sensitive detection of various biomarkers.

A point-of-care chemiluminescence immunoassay for pepsinogen I enables large-scale community health screening

Pepsinogen I (PGI) can reflect the morphology and function of the gastric mucosa. Accordingly, the large-scale community health screening of PGI can dramatically increase the early diagnosis rate of gastric cancer. However, PGI testing can only be carried out in comprehensive hospitals and health examination centers. To ameliorate this issue, a point-of-care chemiluminescent immunoassay for PGI was developed in a fully automated miniaturized instrument. This instrument was especially developed for health check-ups in the grassroots communities; its volume of which is only 0.18 m³. Critically, the entire detection process for a single sample only requires 20 min, and the samples can be loaded continuously, making the method suitable for high-throughput analysis. The assay displayed an excellent detection limit of 0.048 ng/mL with a broad detection range of 0-200 ng/mL. Furthermore, this assay exhibited high sensitivity and specificity, had low intra- and inter-assay coefficients of variation (<10%), and was not affected after storage at 37 °C for 7 days. The assay was used to detect PGI in 95 clinical serum samples, and the results were highly correlated with those that were clinically tested (correlation coefficient, R² = 0.998). Hence, the method established in this work has great application value and can be broadly applied for the large-scale screening of gastric cancer in resource-limited areas.

A quantitative detection of Cardiotrophin-1 in chronic heart failure by chemiluminescence immunoassay

Background

Cardiotrophin‐1 (CT‐1) is a cytokine that could induce cardiomyocytes hypertrophy and dysfunction. Plasma CT‐1 might serve as a cardiac biomarker both in diagnosis, staging, and prognostic assessment of heart failure.

Methods

In this study, a one‐step paramagnetic particles‐based chemiluminescence immunoassay (MPs‐CILA) for rapid and sensitive detection of plasma CT‐1 was established. Plasma samples were directly incubated with biotin‐labeled anti‐CT‐1 antibody (bio‐Ab) and acridine ester labeled anti‐CT‐1 antibody (AE‐Ab) to form sandwiched complex. The sandwiched CT‐1 was then captured by streptavidin modified paramagnetic particles (MPs‐SA) for rapid separation and signal generation.

Results

The proposed MPs‐CLIA presents a laudable linear relationship ranging from 7.8 pg/mL to 200 ng/mL with a detection limit of 1.0 pg/mL. The recoveries of spiked human plasma samples at low (10pg/mL), medium (100 pg/mL), and high (800 pg/mL) levels of CT‐1 were 96%, 104%, and 110% respectively. The intra‐analysis coefficient variation (CVs) of the 3 samples was 8.92%, 6.69%, and 3.54%, respectively. And the inter‐analysis coefficient variation (CVs) was 9.25%, 10.9%, and 4.3%, respectively. These results strongly indicate high sensitivity, wide linear range, acceptable precision, and applicable reproducibility of the proposed method to detect plasma level of CT‐1. Finally, Plasma CT‐1 from 140 subjects with or without chronic heart failure was analyzed to assess the clinical application of MPs‐CILA.

Conclusions

Noteworthily, the MPs‐CLIA method is highly automated such that it is suitable for high‐throughput detection of CT‐1 in clinical inspection.

Sensitive Detection of C-Reactive Protein by One-Step Method Based on a Waveguide-Mode Sensor

One-step biosensing methods enable the quick and simplified detection of biological substances. In this study, we developed a sensitive one-step method on the basis of a waveguide-mode sensor, which is an optical sensor utilizing waveguide-mode resonance and evanescent light. Streptavidin-conjugated and gold-nanoparticle-conjugated antibodies were reacted with a target substance and applied onto a biotinylated sensing plate. The target substance was detected by observing changes in sensor signals caused by binding the immunocomplex to the sensing surface. Performance of the developed one-step method was examined using a C-reactive protein (CRP) as a target substance. A sensor signal corresponding to the concentration of CRP was obtained. The minimal detectable CRP concentration of the developed method was 10 pM. The developed method greatly simplifies quantitative protein detection without reducing sensitivity.

A sensitive and rapid chemiluminescence immunoassay for point-of-care testing (POCT) of copeptin in serum based on high-affinity monoclonal antibodies via cytokine-assisted immunization

Purpose: Antibodies are key reagents in the development of immunoassay. We attempted to develop high-performance CPP immunoassays using high-affinity monoclonal antibodies prepared via cytokine-assisted immunization.

Methods: We used fetal liver tyrosine kinase 3 ligand (Flt3L), CC subtype chemokine ligand 20 (CCL20), and granulocyte-macrophage colony-stimulating factor (GM-CSF) to assist traditional subcutaneous immunization of preparing high-affinity monoclonal antibodies, and further to develop high-performance immunoassay methods for CPP.

Results: This novel immune strategy significantly enhanced immune response against CPP. Six anti-CPP monoclonal antibodies (mAbs) with high affinity were successfully screened and selected for application in a fully automated magnetic chemiluminescence immunoassay (CLIA). This robust and rapid assay can efficiently detect CPP in the range of 1.2–1250 pmol L^–1 with a detection limit of 6.25 pmol L^–1. Significantly, the whole incubation process can be completed in 30 min as compared to about 4.5 hr for the control ELISA kit. Furthermore, this assay exhibited high sensitivity and specificity, low intra-assay and inter-assay coefficients of variation (CVs < 15%). The developed assay was applied in the detection of CPP in 115 random serum samples and results showed a high correlation with data obtained using a commercially available ELISA kit (correlation coefficient, 0.9737).

Conclusion: Our assay could be applied in the point-of-care testing of CPP in the serum samples, and also the method developed in this study could be adopted to explore the detection and diagnosis of other biomarkers for various diseases.

Fabrication of a novel and ultrasensitive label-free electrochemical aptasensor for detection of biomarker prostate specific antigen

In this study, a novel and efficient aptasensor based on immobilization of thiol terminated prostate specific antigen (PSA) binding DNA aptamer onto Au nanoparticles/fullerene C₆₀-chitosan-ionic liquid/multiwalled carbon nanotubes/screen printed carbon electrode has been fabricated for ultrasensitive aptasensing of biomarker PSA. Formation of PSA-aptamer complex caused a variation in electrochemical impedance spectroscopic (EIS) and differential pulse voltammetric (DPV) responses of the aptasensor which enabled us to aptasensing of the PSA by EIS and DPV methods. Morphology and electrochemical properties of the fabricated aptasensor were examined by scanning electron microscopy (SEM), cyclic voltammetry (CV) and EIS. The aptasensor was successfully applied to the determination of PSA by EIS and DPV in the range of 1-200 pg mL^-1 with a limit of detection (LOD) of 0.5 pg mL^-1 and 2.5-90 ng mL^-1 with a LOD of 1.5 ng mL^-1, respectively. This aptasensor exhibited outstanding anti-interference ability towards co-existing molecules with good stability, sensitivity, repeatability and reproducibility. Practical application of the aptasensor was examined with analysis of the PSA levels in serum samples obtained from patients with prostate cancer using both the aptasensor and a reference method. The results revealed the proposed system to be a promising candidate for clinical analysis of PSA.

Selected landscape phage probe as selective recognition interface for sensitive total prostate-specific antigen immunosensor

The level of total prostate-specific antigen (t-PSA) is generally known as the key index of prostate cancer. Here, phage probes against t-PSA were selected from f8/8 landscape phage library. After three rounds of biopanning, four t-PSA-binding phage clones were isolated and identified by the DNA sequencing. Based on the phage capture assay, the phage clone displaying the fusion peptide ATRSANGM showed highest affinity and specificity against t-PSA. Subsequently, the t-PSA-specific phage was used as t-PSA capture probe in a sandwich enzyme-linked immunosorbent assay (ELISA) and differential pulse voltammetry (DPV) assay systems. Both assay methods showed high specificity and acceptable reliability for real serum samples analysis. By comparison, DPV method showed wider linear range (0.01-100 ng mL^-1) and lower limit of detection (3 pg mL^-1) than those (3.3-330 ng mL^-1 and 1.6 ng mL^-1) of ELISA. Moreover, DPV system showed smaller distinction to the authoritative method in real samples assay. Excitingly, the phage probe based DPV immunosensor showed high sensitivity for the detection of t-PSA and LOD achieved the pg mL^-1 level, which was far lower than those values (usually above 0.1 ng mL^-1) for reported immunosensors based on antibodies. Due to the biocompatibility, multivalency, stability, and high structural homogeneity, the t-PSA-specific landscape phage demonstrates as a novel specific interface in biosensors.

Target-activatable gold nanoparticle-based aptasensing for protein biomarkers using stimuli-responsive aggregation

An ultrasensitive and selective light-scattering (LS) aptasensor for prostate specific antigen (PSA) was developed based on bifunctional DNA decorated gold nanoparticles (Au NPs) by use of target stimuli-responsive assembly. Both binding sequence poly adenine (poly(dA), Domain I) and the recognition sequence aptamer (Domain II) of bifunctional ssDNA were in favor of the sensitivity for the fabricated light-scattering aptasensor due to modulated the lateral spacing of DNA on Au NPs surface and possessed strong antigen binding affinity, respectively. And they efficiently promoted the Au NPs aggregation and activated the signal of light-scattering of aptasensor. The formation of aptamer-PSA complex induced conformational transformation of the aptamer on the surface of the Au NPs-based aptasensor and then tuned the interparticle distance of gold nanoparticle assemblies. The larger scattering particles, the higher light-scattering intensity. Target stimuli-responsive aggregation behavior of Au NPs lit up the light-scattering signal of aptasensor. As the concentration of PSA increased, the light-scattering intensity gradually enhanced. The aptasensor response for PSA detection was in the linear range from 0.01 ng/mL to 20 ng/mL with the detection limit of 2 pg/mL. The thiol-free Au NPs-based light-scattering aptasensor has exceptional performances with ultrasensitivity and high selectivity besides the advantage of economic and facile fabrication. Moreover, the proposed target-activated aptasensor was applied for the detection of PSA in serum samples and demonstrated great potential in clinical applications.

A full-automated magnetic particle-based chemiluminescence immunoassay for rapid detection of cortisol in milk

A sensitive full-automated micromagnetic particles (MMPs) based competitive chemiluminescent immunoassay (CLIA) was developed to detect cortisol in milk. Polyclonal antibody (pAb) with good specificity against cortisol was produced. The antigen (cortisol-OVA) was labeled with acridinium ester (cortisol-OVA-AE) as signal tracer. During the detection, the free cortisol in sample will compete with cortisol-OVA-AE for binding to pAb. To capture pAb, MMPs conjugated with goat anti-rabbit IgG was added. The whole immunoassay process (exclude sample pretreatment) was performed by automatic chemiluminescence immunoassay instrument, which could consume less test time (within 40 min) and avoid error from manual operation. The method showed a good detection limit of 0.12 ng/mL, a broad linear range from 0.42 to 72.27 ng/mL for cortisol detection, negligible cross-reactivity with related analogues and satisfied recovery (84.3%-102.3%) for spiked milk samples test. Simultaneously, since the results of proposed method had no significant difference with those of LC-MS/MS, the proposed method was confirmed to have a potential applicability for rapidly monitoring cortisol in the food.

Development of a phage chemiluminescent enzyme immunoassay with high sensitivity for the determination of imidaclothiz in agricultural and environmental samples

In this study, we isolated six phage-displayed peptides by biopanning phage-displayed peptide libraries on an immobilized anti-imidaclothiz monoclonal antibody. After analyzing the relative sensitivity of the individual phage-displayed peptides, we subsequently developed and optimized both a phage enzyme immunoassay (P-ELISA) and a phage chemiluminescent enzyme immunoassay (P-CLEIA) to improve the sensitivity and linear range of imidaclothiz assays. The P-CLEIA (50% inhibition concentration (IC₅₀) of 0.86ngmL^-1, linear range of 0.13-5.84ngmL^-1) was more sensitive and had a wider linear range compared to the P-ELISA (IC₅₀ of 1.45ngmL^-1, linear range of 0.55-3.82ngmL^-1). Besides, the sensitivities of the P-ELISA and P-CLEIA were increased by >4-fold and 8-fold, respectively as compared to homologous immunoassays developed using the same monoclonal antibody. Neither method had significant cross-reactivity with the analogues of imidaclothiz except for imidacloprid. Recoveries of the P-ELISA and P-CLEIA for imidaclothiz in paddy water, soil, cabbage, rice, apple, pakchoi, pear and tomato samples were 72.3-101.3% and 73.9-102.6%, respectively. The P-ELISA and P-CLEIA detected imidaclothiz in the authentic samples, and showed good correlation with results obtained from high-performance liquid chromatography (HPLC).

Plasma from exercised rats administered to sedentary rats induces systemic and tissue inflammation

Recent studies have consistently supported the active role of blood in mediating biochemical and physiological tissue adaptations. However, no study has investigated the possible contribution of circulating factors in an exercise setting. The aim of the study was to investigate the role of circulating factors in exercise adaptations by chronically administering to sedentary animals blood plasma collected from acutely exercised animals. Phase 1: Blood plasma was collected from rats that swam to exhaustion and from sedentary rats. Phase 2: Other rats were divided into two groups (n = 20 per group): the first group involved rats that were injected intravenously with blood plasma originating from rats that previously swam to exhaustion, the second group consisted of rats that were injected intravenously with blood plasma originating from sedentary rats. Tail‐vein injections (2 mL/kg) were performed daily for 21 consecutive days. Inflammatory markers (C‐reactive protein, interleukins‐1α, 2, 6, 8, 10 and tumor necrosis factor‐a) were measured in blood plasma, muscle, and adipose tissue. Sedentary rats administered with plasma from exercised rats had significantly higher levels in all inflammatory markers measured in blood, skeletal muscle and adipose tissue, compared to the sedentary rats administered with resting plasma. Our data demonstrate that administration of “exercised” blood to sedentary rats induced inflammation in plasma, muscle and adipose tissue. Exercise adaptations are not solely due to intrinsic processes in muscle or adipose tissue. Blood factors also play a crucial role in mediating signals for tissue adaptations.

Nanomaterial-based biosensors for detection of prostate specific antigen

Screening serum for the presence of prostate specific antigen (PSA) belongs to the most common approach for the detection of prostate cancer. This review (with 156 refs.) addresses recent developments in PSA detection based on the use of various kinds of nanomaterials. It starts with an introduction into the field, the significance of testing for PSA, and on current limitations. A first main section treats electrochemical biosensors for PSA, with subsections on methods based on the use of gold electrodes, graphene or graphene-oxide, carbon nanotubes, hybrid nanoparticles, and other types of nanoparticles. It also covers electrochemical methods based on the enzyme-like activity of PSA, on DNA-, aptamer- and biofuel cell-based methods, and on the detection of PSA via its glycan part. The next main section covers optical biosensors, with subsections on methods making use of surface plasmon resonance (SPR), localized SPR and plasmonic ELISA-like schemes. This is followed by subsections on methods based on the use of fiber optics, fluorescence, chemiluminescence, Raman scattering and SERS, electrochemiluminescence and cantilever-based methods. The most sensitive biosensors are the electrochemical ones, with lowest limits of detection (down to attomolar concentrations), followed by mass cantilever sensing and electrochemilumenescent strategies. Optical biosensors show lower performance, but are still more sensitive compared to standard ELISA. The most commonly applied nanomaterials are metal and carbon-based ones and their hybrid composites used for different amplification strategies. The most attractive sensing schemes are summarized in a Table. The review ends with a section on conclusions and perspectives.

Quantitative determination of VEGF165 in cell culture medium by aptamer sandwich based chemiluminescence assay

In this work, we have developed a sensitive and selective chemiluminescence (CL) assay for vascular endothelial growth factor (VEGF165) quantitative detection based on two specific VEGF165 binding aptamers (Apt). VEGF is a predominant biomarker in cancer angiogenesis, and sensitive detection method of VEGF are highly demanded for both academic study and clinical diagnosis of multiple cancers. In our experiment, VEGF165 was captured in a sandwich structure assembled by two binding aptamers, one capture aptamer was immobilized on streptavidin-coated magnetic beads (MBs) and another VEGF-binding aptamer was labeled by biotin for further phosphatase conjunction. After Apt-VEGF-Apt sandwich was formed on MBs surface, alkaline phosphatase (ALP) was modified to the second aptamer to catalyze CL reaction. By applying 4-methoxy-4-(3-phosphatephenyl)-spiro-(1,2-dioxetane-3,2-adamantane) (AMPPD) as CL substrate, strong signal intensity was achieved. VEGF165 content as low as 1ng/mL was detected in standard spiked samples by our assay, and linear range of working curve was confirmed from 1 to 20ng/mL. Then our method was successfully applied for cell culture medium analysis and on-chip hypoxic HepG2-HUVEC co-culture model study with excellent accuracy equal to ELISA Kit. Our developed assay demonstrated an outstanding performance in VEGF165 quantification and may be further extended to clinical testing of important biomarkers as well as probing microchip cell culture model.

Simultaneous determination of free and total prostate-specific antigen by a magnetic particle-based time-resolved fluoroimmunoassay

OBJECTIVES

In this paper, a novel, sensitive and rapid method to simultaneously determine the free and total prostate-specific antigen (fPSA and tPSA) in serum by combining a time-resolved fluoroimmunoassay (TRFIA) and immunomagnetic separation was described.

METHODS

The new approach uses magnetic particles as an immobilization matrix and means of separation, whereas the luminescent europium (Eu) and samarium (Sm) chelates are used as probes. The proposed method was evaluated via a single-step, sandwich-type TRFIA immunoassay of tPSA and fPSA as model analytes in serum.

RESULTS

A new one-step method to simultaneously detect fPSA and tPSA in less than 15 minutes was built up with the detection limits 0.006 ng/mL for fPSA and 0.05 ng/mL for tPSA. The assay ranges for fPSA and tPSA were both 0.5-100 ng/mL, whereas the average recovery of those two obtained by our original mode were 95.9% and 95.3%, respectively. The present new TRFIA method carrying larger reproducibility, higher recovery, and sensitive specificity was demonstrated to be widely acceptable.

CONCLUSIONS

This simultaneous determination method containing a fast and sensitive approach can be put into an important position to screening large quantities of specimen, and be commonly applied to the clinical determination of fPSA and tPSA in human serum.

Electrochemical bioassay development for ultrasensitive aptasensing of prostate specific antigen

A densely packed gold nanoparticles on the rGO-MWCNT platform was used as the basis for an ultrasensitive label-free electrochemical aptasensor to detect the biomarker prostate specific antigen (PSA) in serum. The detection was based on that the variation of electron transfer resistance (R_ct) and differential pulse voltammetry (DPV) current were relevant to the formation of PSA-aptamer complex at the modified electrode surface. Compared with pure AuNPs, rGO-MWCNT and MWCNT/AuNPs, the rGO-MWCNT/AuNPs nanocomposite modified electrode was the most sensitive aptasensing platform for the determination of PSA. Two calibration curves were prepared from the data obtained from the DPV and electrochemical impedance spectroscopy (EIS) by plotting the peak current and R_ct against PSA concentration, respectively. The proposed aptasensor had an extremely low LOD of 1.0pgmL^-1 PSA within the detection range of 0.005-20ngmL^-1 and 0.005-100ngmL^-1 for DPV and EIS calibration curves, respectively. This sensor exhibited outstanding anti-interference ability towards co-existing molecules with good stability, sensitivity, and reproducibility. Clinical application was performed with analysis of the PSA levels in serum samples obtained from patients with prostate cancer using both the aptasensor and Immunoradiometric assay. The results revealed the proposed system to be a promising candidate for clinical analysis of PSA.

A portable chemiluminescence imaging immunoassay for simultaneous detection of different isoforms of prostate specific antigen in serum

A multianalyte chemiluminescence (CL) imaging immunoassay strategy for sensitive detection of different isoforms of prostate specific antigen (PSA) was developed. The microtiter plates were fabricated by simultaneously immobilizing of free-PSA (f-PSA) and total-PSA (t-PSA) capture antibody on nitrocellulose (NC) membrane. Each of the array were spotted in replicates of six spots within a spacing of 2mm. 16 or 48 detection wells were integrated on a single NC membrane and each well could be used as a microreactor and microanalysis chamber. Under a sandwiched immunoassay, the CL signals on each sensing site were collected by a charge-coupled device (CCD), presenting an array-based chemiluminescence imaging. Soybean peroxidase (SBP) was used to label f-PSA or t-PSA monoclonal antibody. With the amplification effects of two enhancers, 3-(10'-phenothiazinyl) propane-1-sulfonate (SPTZ) and 4-morpholinopyridine (MORP), the CL intensity could significantly enhanced, which improved the sensing sensitivity and detection limit. Under the optimal conditions, the linear response to the analyte concentration ranged from 0.01-36.7ng/mL and 0.02-125ng/mL for f-PSA and t-PSA, respectively. The results for the detection of forty serum samples from prostate cancer patients and cancer-free patients showed good agreement with the clinical data, suggesting that the proposed assay had acceptable accuracy. The proposed CL imaging immunoassay possess high throughput and acceptable reproducibility, stability and accuracy, which made it great potential to available to distinguish different isoforms of PSA in serum samples.

The rat closely mimics oxidative stress and inflammation in humans after exercise but not after exercise combined with vitamin C administration

PURPOSE

The purpose of the present study was to directly compare oxidative stress and inflammation responses between rats and humans.

METHODS

We contrasted rat and human oxidative stress and inflammatory responses to exercise (pro-oxidant stimulus) and/or vitamin C (anti-oxidant stimulus) administration. Vitamin C was administered orally in both species (16 mg kg(-1) of body weight). Twelve redox biomarkers and seven inflammatory biomarkers were determined in plasma and erythrocytes pre- and post-exercise or pre- and post-exercise combined with vitamin C administration.

RESULTS

Exercise increased oxidative stress and induced an inflammatory state in rats and humans. There were only 1/19 significant species × exercise interactions (catalase), indicating similar responses to exercise between rats and humans in redox and inflammatory biomarkers. Vitamin C decreased oxidative stress and increased antioxidant capacity only in humans and did not affect the redox state of rats. In contrast, vitamin C induced an anti-inflammatory state only in rats and did not affect the inflammatory state of humans. There were 10/19 significant species × vitamin C interactions, indicating that rats poorly mimic human oxidative stress and inflammatory responses to vitamin C administration. Exercise after acute vitamin C administration altered redox state only in humans and did not affect the redox state of rats. On the contrary, inflammation biomarkers changed similarly after exercise combined with vitamin C in both rats and humans.

CONCLUSIONS

The rat adequately mimics human responses to exercise in basic blood redox/inflammatory profile, yet this is not the case after exercise combined with vitamin C administration.

Ultrafast immunoassays by coupling dielectrophoretic biomarker enrichment in nanoslit channel with electrochemical detection on graphene

Heterogeneous immunoassays usually require long incubation times to promote specific target binding and several wash steps to eliminate non-specific binding. Hence, signal saturation is rarely achieved at detection limit levels of analyte, leading to significant errors in analyte quantification due to extreme sensitivity of the signals to incubation time and methodology. The poor binding kinetics of immunoassays at detection limit levels can be alleviated through creating an enriched analyte plug in the vicinity of immobilized capture probes to enable signal saturation at higher levels and at earlier times, due to higher analyte association and its faster replenishment at the binding surface. Herein, we achieve this by coupling frequency-selective dielectrophoretic molecular dam enrichment of the target biomarker in physiological media to capture probes immobilized on graphene-modified surfaces in a nanoslit to enable ultrafast immunoassays with near-instantaneous (<2 minutes) signal saturation at dilute biomarker levels (picomolar) within ultra-low sample volumes (picoliters). This methodology is applied to the detection of Prostate Specific Antigen (PSA) diluted in serum samples, followed by validation against a standard two-step immunoassay using three de-identified patient samples. Based on the ability of dielectrophoretic molecular dam analyte enrichment methods to enable the detection of PSA at 1-5 pg mL(-1) levels within a minute, and the relative insensitivity of the signals to incubation time after the first two minutes, we envision its application for improving the sensitivity of immunoassays and their accuracy at detection limit levels.

Electrogenerated Chemiluminescence Bioanalytic System Based on Biocleavage of Probes and Homogeneous Detection

A novel electrogenerated chemiluminescence (ECL) bioanalytic system based on biocleavage of a ECL probe and homogeneous detection was designed and utilized for the first time for highly sensitive quantification of proteases to overcome drawbacks from probes directly immobilized on electrodes and commercial ECL biosystems, based on bioaffinity reactions. Prostate-specific antigen (PSA) was taken as a model analyte and ruthenium complex-tagged specific peptide (CHSSKLQK) was designed as an ECL probe (peptide-Ru1). ECL bioconjugated magnetic beads were synthesized through a simple solid-phase synthesis. When analyte PSA was introduced into the suspension of ECL bioconjugated magnetic beads, a biocleavage of the peptide occurred and the cleaved Ru1 part was released from the magnetic beads. ECL measurement was carried out in the presence of co-reactant tripropylamine, using two models. One is homogeneous ECL detection on a bare graphite pencil electrode (PGE), and the other is enriching ECL detection after the cleaved Ru1 part of the peptide was concentrated into the surface film of Nafion/gold nanoparticles modified PGE (AuNPs/Nafion/PGE). The extremely low detection limit of 80 fg/mL and high reproducibility (relative standard deviation (RSD) of 5.4% for six measurements of 0.5 pg/mL) for the detection of PSA were achieved at AuNPs/Nafion/PGE. This work demonstrates that the bioanalytic system designed can not only quantify proteases with high sensitivity and selectivity, but also diminish the complicated electrode process and improve the reproducibility by conducting the biocleavage and transduction steps at different surfaces. It can be easily extended for ECL analysis of other proteases in this system and other detection techniques, including optics and electrochemistry.

Evaluation of a magnetic particles-based chemiluminescence enzyme immunoassay for Golgi protein 73 in human serum

BACKGROUND

Golgi protein 73 (GP73) is regarded as a potential serum biomarker for early diagnosis of hepatocellular carcinoma (HCC). We developed a rapid magnetic particles-based chemiluminescence enzyme immunoassay (MPs-CLEIA) for the determination of serum GP73.

METHODS

Fluorescein isothiocyanate (FITC) and alkaline phosphatase (ALP) were used to label 2 different monoclonal antibodies to GP73. Serum GP73 was captured with labeled antibodies and formed a sandwiched immunoreaction. The magnetic particles (MPs) coated with anti-FITC antibody were used as a means of separation of the GP73 protein from other serum proteins. After adding the enzyme substrate solution, the relative light unit (RLU) was measured. A MPs-CLEIA for serum GP73 was established and evaluated.

RESULTS

The RLU was directly proportional to the concentration of GP73. The method linearity was 5-600 μg/l. Limit of the blank was 2.19 μg/l. The intra- and inter-assay imprecision was <3% and <5%, respectively. The average recoveries were between 95% and 105%. The proposed method showed a good correlation with a commercial ELISA assay (r=0.983, p<0.001). We also evaluated the efficiency of serum GP73 measurement for the diagnosis of HCC using this assay. The area under the receiver operating characteristic curve was 0.822 (95% CI, 0.73-0.89), and the sensitivity and specificity, with cut-off value of 115.6 μg/l, were 75.4% and 92.1%, respectively.

CONCLUSIONS

The proposed method demonstrates an acceptable performance for quantifying serum GP73. This assay could be appropriate for routine use in clinical laboratories.

3D sandwich-type prostate specific antigen (PSA) immunosensor based on rGO–MWCNT–Pd nanocomposite

A signal amplifying sandwich-type immunosensor with a wide linear range and a low detection limit is developed with potential clinical and diagnostic applications.

Voltammetric aptasensor combined with magnetic beads assay developed for detection of human activated protein C

A sensitive and selective label free voltammetric aptasensor based on magnetic beads assay was performed for the first time in our study for monitoring of human activated protein C (APC), which is a serine protease (i.e., key enzyme of the protein C pathway). An amino modified DNA aptamer (DNA APT) was covalently immobilized onto the surface of carboxylated magnetic beads (MBs), and then, the specific interaction between DNA APT and its cognate protein, APC, was performed at the surface of MBs. Similarly a biotinylated DNA APT was immobilized onto the surface of streptavidin coated MBs. Before and after interaction process, the oxidation signal of guanine was measured at disposable pencil graphite electrode (PGE) surface in combination with differential pulse voltammetry (DPV) technique and accordingly, the decrease at the guanine signal was evaluated. The biomolecular recognition of APC was successfully achieved with a low detection limit found as 2.35 µg mL(-1) by using MB-COOH based assay. Moreover, the selectivity of this aptasensor assay was tested in the presence of numerous proteins and other biomolecules: protein C (PC), thrombin (THR), bovine serum albumin (BSA), factor Va (FVa) and chromogenic substrate (KS).