Prostate-specific Antigen Assay Research Articles

Prostate-Specific Antigen as an Ultrasensitive Biomarker for Patients with Early Recurrent Prostate Cancer: How Low Shall We Go? A Systematic Review.

Serum prostate-specific antigen (PSA) needs to be monitored with ultrasensitive PSA assays (uPSAs) for oncologists to be able to start salvage radiotherapy (SRT) while PSA is <0.5 µg/L for patients with prostate cancer (PCa) relapsing after a radical prostatectomy (RP). Our systematic review (SR) aimed to summarize uPSAs for patients with localized PCa. The SR was registered as InPLASY2023110084. We searched for studies on Google Scholar, PUBMED and reference lists of reviews and studies. We only included studies on uPSAs published in English and excluded studies of women, animals, sarcoidosis and reviews. Of the 115 included studies, 39 reported PSA assay methods and 76 reported clinical findings. Of 67,479 patients, 14,965 developed PSA recurrence (PSAR) and 2663 died. Extremely low PSA nadir and early developments of PSA separated PSAR-prone from non-PSAR-prone patients (cumulative p value 3.7 × 1012). RP patients with the lowest post-surgery PSA nadir and patients who had the lowest PSA at SRT had the fewest deaths. In conclusion, PSA for patients with localized PCa in the pre-PSAR phase of PCa is strongly associated with later PSAR and survival. A rising but still exceedingly low PSA at SRT predicts a good 5-year overall survival.

Predictive Value of Transrectal Ultrasonic Doppler and Elastographic Features in Prostate Cancer Detection in Lagos University Teaching Hospital.

This study aimed at determining the predictive value (PV) of transrectal ultrasonic Doppler and elastographic features in prostate cancer (PCa) detection among patients in Lagos University Teaching Hospital. This prospective study involved patients that underwent evaluation for PCa. Participants had digital rectal examination (DRE), prostate-specific antigen (PSA) assay, and transrectal ultrasound-guided prostate biopsy using colour Doppler (CD) and elastography. All cores were sent for histopathology. Data were analysed using Statistical Package for the Social Sciences Version 22.0. CD and elastography PV in PCa detection and their relationships to the Gleason score (GS) were analysed (P < 0.05). Seventy men (aged between 45 and 87 years) were enrolled. Forty-three (61.4%) patients had PCa with a mean age of 69.37 ± 8.22years. The sensitivity, specificity, positive PV (PPV), negative PV (NPV) and accuracy of CD were 8.50%, 97.44%, 64.10%, 66.42% and 66.31%, respectively. The sensitivity, specificity, PPV, NPV and accuracy of elastography were 84.21%, 94.59%, 88.89%, 92.11% and 91.07%, respectively. There is a significant association between decreased elasticity (elastography) and PCa detection but a weak association between increased vascularity (CD) and PCa detection. A positive correlation exists between extent of prostatic stiffness and GS.

Bio-conjugated carbon dots for the bimodal detection of prostate cancer biomarkers via sandwich fluorescence and electrochemical immunoassays.

Bimodal detection facilitates the accurate and reliable detection of cancer biomarkers, which can assist in the early diagnosis of cancer. Herein, S-doped carbon dots (OCDs) with a size of 3 nm and blue emission were synthesized by the hydrothermal treatment of onion extract. The S-doped carbon dots were bioconjugated with an antibody (OCDs@PSAAbHRP) to design a nanoprobe for the detection of prostate specific antigen (PSA), an important serum based prostate cancer biomarker. The detection probe enabled the biomodal assay of PSA via fluorescence immunoassay (FIA) and electrochemical immunoassay (ECIA). In both assays, polyethylenimine stabilized polyaniline nanoparticles (PNPs) were used as the immobilization matrix, which played a major role in widening the linear range of biosensors (0.1 to 100 ng ml-1 for ECIA and 5 to 120 ng ml-1 for FIA). Paper-based and smartphone-integrated fluorescence immuno-array developed using the OCDs@PSAAbHRP detection probe provided cost-effective and rapid detection, while the electrochemical immunoassay provided a high sensitivity (7.8 μA ng-1 ml-1 cm-2) and low detection limit (38 pg ml-1) for PSA detection. The role of OCDs in enhancing the sensor performance was deciphered by carrying out detailed electrochemical studies with HRP enzyme-loaded OCDs. The biosensor was used to detect PSA in human blood serum samples and the results were consistent with conventional techniques. Owing to its analytical properties coupled with simplicity, cost-effectiveness, and portability, the bimodal sensor system has potential for application in clinical analysis.

Population-based Organised Prostate Cancer Testing: Results from the First Invitation of 50-year-old Men

BackgroundThe European Union recently recommended evaluation of the feasibility of organised prostate cancer screening. In Sweden, regional population-based organised prostate cancer testing (OPT) programmes were introduced in 2020. ObjectiveTo describe initial participation rates and diagnostic outcomes. Design, setting, and participantsThe three most populated Swedish regions invited all men aged 50 yr to OPT by a letter in 2020–2022. Men with prostate-specific antigen (PSA) ≥3 ng/ml were referred for prostate magnetic resonance imaging (MRI). PSA assays differed across regions. Men with Prostate Imaging Reporting and Data System (PI-RADS) 1–3 and PSA density ≥0.15 ng/ml/cm3 or PI-RADS 4–5 were referred for a biopsy. Data were obtained from the Swedish Register for Organised Prostate Cancer Testing. Outcome measurements and statistical analysisOverall and regional participation rates, PSA distributions, PI-RADS score distributions, cancer detection, and treatment were evaluated. Results and limitationsA total of 23 855 (35%) of 68 060 invited men participated; 696 (2.9%) had PSA ≥3 ng/ml, and of them, 306 (44%) had a biopsy indication and 221 (32%) had a biopsy. On biopsy, 93 (42%) had Gleason grade group ≥2 (0.39% of PSA-tested men) and 44 (20%) Gleason grade group 1 cancer. Most men with cancer had treatment with curative intent (70%) or were under active surveillance (28%). Across regions, proportions of men with PSA ≥3 ng/ml ranged from 2.3% to 4.0%, and those with PI-RADS score 4–5 ranged from 12% to 21%. A limitation is that results are applicable only to first testing of men in their early 50s. ConclusionsThe OPT programmes are feasible with good compliance to the diagnostic pathway. The use of MRI and PSA density avoided a biopsy for over half of the men with PSA ≥3 ng/ml. Inter-regional differences in diagnostic outcomes show a need for standardisation of the diagnostic pathway’s components. Patient summaryWe report the diagnostic outcomes of inviting 68 000 50-yr-old men to organised prostate cancer testing.

Photocurrent-polarity switching between methylene blue-loaded liposome and iodine-doped BiOCl for in-situ amplified immunoassay

This work designed a liposome-mediated photocurrent polarity switching immunosensor depending on the reversed photocurrent of iodine-doped BiOCl (I-BOC) nanoflowers induced by the released methylene blue (MB) for the detection of prostate-specific antigen (PSA). Initially, MB-loaded liposomes as indicators were confined within the microplates to participate in the sandwiched immunoreaction and lysed under the treatment of Triton X-100 to release numerous MB. Owing to the host-guest recognition between β-cyclodextrin (β-CD) and MB, the released MB was immobilized on the β-CD-modified I-BOC/FTO electrode and triggered the photocurrent polarity reversal from cathodic photocurrent to anodic photocurrent. The sensing platform realized an accurate and sensitive assay of PSA due to the effective elimination of false-positive/negative signals in a linear range of 0.02–50 ng mL−1 with a limit of detection of 12 pg mL−1. Furthermore, this work not only conjugated liposome-assisted signal amplification strategy with the photocurrent polarity switching system but also provided a novel pathway for various protein determinations.

B-042 Evaluation of the Analytical Performance of Three Prostate-specific Antigen Immunoassays on the Atellica CI 1900 Analyzer

Abstract Background The Atellica® CI 1900 Analyzer is an automated, mid-throughput, integrated chemistry and immunoassay analyzer employing both Atellica CH and Atellica IM assays. This study was designed to evaluate the analytical performance of the Atellica IM Prostate-Specific Antigen (PSA)*, Complexed Prostate-Specific Antigen (cPSA)*, and Free Prostate-Specific Antigen (fPSA)* assays on the Atellica CI 1900 Analyzer. Methods The Atellica CI 1900 PSA, cPSA, and fPSA assays use the same reagents and calibrators as the comparable Atellica IM assays. Limit of quantitation (LoQ), precision, and method comparison (MC) were used as performance indicators for the Atellica CI 1900 Analyzer. LoQ studies were performed in accordance with CLSI EP17-A2 using native and contrived human serum samples. Precision studies were performed according to CLSI EP05-A3 using contrived human serum samples. One aliquot of each sample pool was tested in duplicate in two runs per day &amp;gt;2 hours apart on each analyzer for &amp;gt;20 days. MC studies were performed according to CLSI EP09-A3. Individual native human serum samples were analyzed using the Atellica IM assays on both the Atellica IM and Atellica CI 1900 Analyzers. Results LoQ is defined as the lowest amount of analyte in a sample at which the within-laboratory %CV is ≤20%. Representative precision and MC results for each assay across indicated sample ranges are listed in the table. Over the three assays tested, repeatability and within-lab %CVs were ≤8.0% and ≤15.5%, respectively. Slopes determined by the Deming linear regression model were approximately equal to 1. Conclusion Evaluation of the Atellica IM PSA, cPSA, and fPSA assays using the Atellica CI 1900 Analyzer demonstrated good precision and equivalent performance compared to the same assays on the Atellica IM Analyzer. *The products/features mentioned here are not commercially available in all countries. Their future availability cannot be guaranteed. fPSA assay is not available for sale in US.

Versatile FeMoOv nanozyme bipolar electrode electrochemiluminescence biosensing and imaging platform for detection of H2O2 and PSA

In this work, a unique FeMoOv nanozyme-bipolar electrode (NM-BPE) electrochemiluminescence (ECL) biosensing and imaging platform was proposed for the first time to realize sensitive detection of target hydrogen peroxide (H2O2) and prostate specific antigen (PSA). Considering the advantage that the cathode and anode poles of the bipolar electrode (BPE) can be modified respectively, this work was carried out using anode equipped with ECL reagent bipyridine ruthenium (Ru(bpy)32+), and cathode equipped with the Fe-doped molybdenum oxide/Au nanoparticles (FeMoOv/AuNPs) with excellent peroxidase (POD) and catalase (CAT)-like activity. Because FeMoOv/AuNPs show efficient enzyme catalysis effect and can greatly promote the decomposition of H2O2, thus the electron transfer rate in the NM-BPE system would be much accelerated to enhance the ECL signal of Ru(bpy)32+. Based on this principle, this work not only realized sensitive detection of H2O2, but also ingeniously designed an sandwich immunosensor using FeMoOv/AuNPs as recognition probe to mediate the ECL response on the anode, achieving highly sensitive detection of PSA. Furthermore, a unique mobile phone ECL imaging system was developed for assay of PSA at different concentrations, which opened a new portable imaging sensing device for bioassays. This work was the first time to combine nanozymes with bipolar electrodes for ECL analysis and imaging, which not only broadened the applications of nanozymes, but also pioneered the new joint ECL research technique of bipolar electrode and ECL imaging in bioassays, showing great application prospect for multiple detection of proteins, nucleic acids and cancer cells.

A label-free and ratiometric fluorescent immunosensor by integrating CRISPR/Cas 12a and 3D DNA nanomachine

Sensitive, selective, especially label-free detection of disease relevant protein biomarkers is highly valuable for clinical diagnosis and disease process monitoring but remains a challenge. Herein, with prostate specific antigen (PSA) as a model target, we have designed a label-free ratiometric fluorescent immunosensor based on three-dimensional (3D) DNA walker and the powerful clustered regularly interspaced short palindromic repeat (CRISPR)/Cas system, with poly(thymine) templated Cu nanoclusters and DAPI as signals. The aptamer-linked activator DNA was designed to convert target recognition event into activate deoxyribonuclease activity of CRISPR/Cas12a system and further cleave oligonucleotides. The cleavage behavior leads to the quenching of copper nanoclusters and stagnation of the cascade amplification progress of 3D DNA nanomachine. The DNA machine is constructed from primer DNA and silica nanospheres loaded by double-stranded DNA (dsDNA) with prominent 3′ end, and movement of the primer DNA is powered by exonuclease (Exo) III via a burnt-bridge mechanism. Without primer DNA, the dyes (DAPI) were embedded in the complementary DNA and emit strong fluorescence. The practical applicability of the biosensor was demonstrated by assay of PSA in human serum with satisfactory result. In addition, this completely label-free method, reduced consumption of antibody, greatly simplify the procedures and saving cost.

A Comparative Study of Prostate Specific Antigen (PSA) Point-of-Care-Testing (POCT) Techniques

Background: Prostate Specific Antigen (PSA) testing is widely used to diagnose and monitor clinical progress in patients with prostate cancer. The availability of various new Point-of-Care-Testing (POCT) equipment for PSA demands that the performance characteristics of these equipment be assessed before introducing them into clinical use to ensure accuracy and reliability. Objectives: To compare the i-CHROMA® automated immunofluorescence serum total PSA assay with the Accubind® Enzyme Linked Immuno-Sorbent Assay (ELISA) as POCT among patients with suspected prostate cancer. Methods: The study was conducted at the Obafemi Awolowo University Teaching Hospitals Complex (OAUTHC), Ile-Ife, Nigeria. Blood samples drawn from 20 consecutively selected patients were analysed for PSA using the i-CHROMA® immunofluorescence kit once and with the Accubind® ELISA protocol twice. Results: The mean PSA using Accubind® ELISA was 12.9ng/ml, while it was 14.5ng/ml with the i-CHROMA® immunofluorescence assay. The bias between the two methods was 1.6ng/ml. The two methods had a good correlation: Passing Bablok regression equation was y = 1.264604x – 0.0300469, and the Spearman correlation coefficient between the two measurements was high (r = 0.956; Confidence Interval 0.889 - 0.983; p&lt;0.0001). Agreement between the two methods was statistically satisfactory as the mean values of the samples fell within the 95% Confidence Interval of the differences on the Bland Altman plot. Conclusion: The i-CHROMA® POCT assay showed good correlation and agreement with the well-known ELISA method. Therefore, the method is recommended for use in monitoring PSA in patients with prostatic cancer.

Potential New Approaches for Prostate Cancer Management in Resource-Limited Countries in Africa.

Prostate cancer is a major male malignancy in many sub-Saharan countries in Africa. Because of resource limitations, screening, early detection, diagnosis, and curative treatments are not available for many men on the subcontinent, and there are even barriers to the treatment of advanced-stage metastatic prostate cancer. We are making the case for new approaches to the detection, diagnosis, and treatment of this malignancy in sub-Saharan Africa and other low-resource regions-approaches that differ from the ones available and used in high-income countries. The development of one-step dipstick-type detection assays of serum prostate-specific antigen (PSA) offers an approach to prostate cancer detection, treatment and monitoring that circumvents issues related to laboratory quality control and is also low-cost. Curative-intent treatments of early-stage prostate cancer are often unavailable in low-resource contexts, and most prostate cancers are not detected in Africa until they are at an advanced stage. Hence, androgen deprivation treatments, including orchiectomy and older low-cost drugs, offer feasible and affordable approaches to prolong survival and sustain a reasonable quality of life. However, clinical trials are needed to identify which of these androgen deprivation treatments are most efficacious and best tolerated to make progress in providing medical care for men with prostate cancer in sub-Saharan Africa and other low- and lower-middle-income areas around the world.

Bioorthogonal chemistry-based high-efficient quantum dots binding boosts the detection sensitivity of plasmon-enhanced fluorescence platform for immunoassay

Although plasmon-enhanced fluorescence (PEF) technology has been demonstrated its potential in protein detection for disease early diagnosis, its detection sensitivity still has a big gap compared to that of methods featured with single-molecule detection ability. Herein, inspired by the properties of catalyst-free bioorthogonal chemistry between 1,2,4,5-tetrazine (Tz) and trans-cyclooctene (TCO) being capable of improving the nanoparticle binding efficiency, we initially incorporate semiconductor quantum dots (QDs) into PEF-based suspension microarray platform as the signal reporter and evaluate its performance for biomarker prostate-specific antigen (PSA) detection by comparing with traditional fluorescence protein-based methods. In our assay, Tz-tagged QDs could be readily absorbed onto the sandwich immunocomplex composed of capture antibody, target PSA and TCO-labelled detection antibody for signal output. To improve the QDs binding efficiency, detection performance obtained from QDs-conjugated detection antibody as the reporter prepared by the same bioorthogonal chemistry reaction was also evaluated. For the evaluation of its potential in practical application, the performance including detection sensitivity and dynamic range of the proposed method for PSA assay in clinical sera samples using commercially-available PEF-based planar microarray as the control was discussed, which revealed that the nanoparticle-binding efficiency base on traditional SA/avidin method could be dramatically improved by the proposed method.

Consistency and diagnostic accuracy of 4 assays in the detection of the total and free prostate-specific antigen.

The lack of interchangeability among prostate-specific antigen (PSA) assays causes difficulties in clinical interpretation. The currently available mainstream assays for PSA were based on Western populations, but it is not clear whether these assays yield different results in prostate cancer (PCa) screening in Chinese populations. A total of 163 men with a total PSA (tPSA) level of 2-10 µg/L scheduled for prostate biopsy were enrolled in this study. The levels of the tPSA and free PSA (fPSA) were detected by the Beckman (using the Hybritech calibration), Roche, Abbott, and Mindray (using the World Health Organization's calibration). Methodological comparison were performed according to EP9-A3 of the Clinical and Laboratory Standards Institute, USA. With pathological diagnosis as the gold standard, the predictive accuracy of the biomarkers was quantified as the area under the receiver operating characteristic curve (AUC) for each of the four methods. A total of 32 PCa patients and 131 patients with benign prostate disease were included in this study. The tPSA levels detected by the Roche, Abbott, and Mindray showed good consistency with Beckman but not of the fPSA levels. Compared to the Beckman tPSA values, the measured values were 1.1% higher for Roche, 2.1% higher for Abbott, and 6.7% higher for Mindray. The fPSA levels measured by Roche, Abbott, and Mindray were 5.4% lower, 22.1% higher, and 4.6% higher than Beckman, respectively. When the tPSA was 4 ng/mL, the diagnostic performance (sensitivity, specificity, positive predictive value, negative predictive value, and missed diagnosis rate) was similar among these 4 assays. When the %fPSA was 16%, Abbott had the highest missed diagnosis rate (37.50%), while Mindray had a sensitivity of 81.25%, the highest negative predictive value (93.88%), and the lowest missed diagnosis rate (18.75%). When the tPSA level is 2-10 ng/mL, the Mindray, like the Roche and Abbott, has good consistency with the Beckman in detecting tPSA, which makes it possible to relieve the pressure of clinical interpretation. However, 4 assays using the same %fPSA cut-off may lead to diverse missed diagnosis rates for PCa screening in China.

Association of Haplotypes in Exon 4 of KLK2 Gene with Raised Serum Prostate-Specific Antigen

The standard diagnostic modalities for Prostate Cancer (PC) include serum Prostate-Specific Antigen (PSA) assay, Digital Rectal Examination (DRE), and histological examination of prostate biopsy. They are limited by low predictive potential and inability to predict which patients are at risk of developing metastatic disease. The aim of this study is to investigate the exon 4 of the KLK2 gene of subjects for changes in its nucleotide sequences (SNPs) and determine the correlation of these changes with serum PSA in an Igbo population of Nigeria. One hundred male subjects aged 40 years and above, who gave their consent, were used for the study. Their PSA determinations were done using ELISA technique while genetic studies were carried out using real-time PCR. tPSA, fPSA, and % fPSA of the subjects ranged between 0.8% - 18.30%, 0.10% - 1.60% and 0.0% - 0.7% respectively. Of the 100 subjects, 28 subjects had tPSA levels above 4.0 ng/ml with a mean of 7.10 (±3.30) ng/ml. Those with tPSA less than 4 ng/ml had a mean of 1.87 (±0.85) ng/m. 15 subjects showed SNPs with a mean tPSA of 6.87 (±4.82) ng/ml while the remaining 85 subjects without SNPs had a mean of 1.86 (±0.80) ng/ml. Results from direct DNA sequencing showed 11 SNPs. Ten subjects are curated in SNP database while one is uncurated. The Chi-square test showed significant association (p = 0.00) between tPSA levels and SNPs mutation (X2 = 17.35, p = 0.00). A Kruskal-Wallis test demonstrated that the positional arrangement of the SNP mutations had no effect on PSA-total or free-values (H (10) = 10.92, p = 0.28; H (10) = 10.07, p = 0.38 respectively). Two SNPs: rs6072 and rs74478031 were associated with elevated PSA levels (p < 0.05). Their presence, therefore, has the potential to serve, in conjunction with raised PSA, as biomarkers of prostate cancer in the study population.

Managing the impact of inter-method bias of prostate specific antigen assays on biopsy referral: the key to move towards precision health in prostate cancer management.

We assessed the inter-method bias of total (tPSA) and free (fPSA) prostate-specific antigen (PSA) immunoassays to establish if tPSA-based risk thresholds for advanced prostate cancer (PCa), obtained from one method (Roche) can be converted into the corresponding concentrations assayed by other methods. Then we evaluated the impact of the bias of tPSA and fPSA on theestimation of the %f/tPSA ratio and performed a re-calibration of the proposed thresholds for the %f/tPSA ratio according to the assay used. tPSA and fPSA were measured in 135 and 137 serum samples, respectively by Abbott Alinity i, Beckman Access Dxl, Roche Cobas e801, and Siemens Atellica IManalytical platforms. Scatterplots, Bland-Altman diagrams, Passing-Bablok (PB) were used to inspect and estimate the systematic and proportional bias between the methods. The linear equations with confidence intervals of the parameter estimates were used to transform the tPSA risk thresholds for advanced PCa into the corresponding concentrations measurable by the other analytical methods. To construct a correction coefficient for converting the %f/tPSA ratio from one method to the other, PB and non-parametric boostrapping were used. The inter-method bias is not constant but strictly linear allowing the conversion of PSA results obtained from Roche into the other assays, which underestimate tPSA vs. Roche. Siemens and Abbott vs. Roche and Beckman assays, being characterized by a positive and a negative proportional bias for tPSA and fPSA measurements, tend to overestimate the %f/tPSA ratio. There is a consistent risk to miss advanced PCa, if appropriate conversion factors are not applied.

Optical fiber peptide-sensor for ultrasensitive detection of prostate specific antigen

We develop the first optical fiber-based peptisensor with chemiluminescent detection, and apply it for ultrasensitive detection of prostate-specific antigen (PSA), an important biomarker for early diagnosis of prostate disease. Optical fiber is used not only as the carrier of the biological recognition elements (the specific biotinylated peptides, bio-KQLKSSHC), but also for the excellent light conduction for chemiluminescence signal output. The peptisensor is easily fabricated and gold nanoparticles (AuNPs) modified with horseradish peroxidase (HRP) are employed as the signal label for chemiluminescent detection. By combining the streptavidin-biotin system and the large surface area of AuNPs, both the peptide loading amount and the chemiluminescence signal are enhanced, thus the response of the peptisensor is greatly improved with a wide linear range of 0.80 pg/mL −100 ng/mL (2.42 ×10−9-3.03 ×10−4 nmol) and a low limit-of-detection of 0.30 pg/mL (9.09 ×10−10 nmol). The HRP@AuNPs@peptide optical fiber peptisensor exhibiting good reproducibility and selectivity for PSA assays. Our study indicates that the optical fiber-based peptisensors would be of value for sensitive detection of biomarkers with advantages of low-cost, easy operation and possibly for miniaturization, thus would they have great potential application in vitro diagnosis.

Fluorescent Immunoassay with a Copper Polymer as the Signal Label for Catalytic Oxidation of O-Phenylenediamine.

This work suggested that Cu2+ ion coordinated by the peptide with a histidine (His or H) residue in the first position from the free N-terminal reveals oxidase-mimicking activity. A biotinylated polymer was prepared by modifying His residues on the side chain amino groups of lysine residues (denoted as KH) to chelate multiple Cu2+ ions. The resulting biotin-poly-(KH-Cu)20 polymer with multiple catalytic sites was employed as the signal label for immunoassay. Prostate specific antigen (PSA) was determined as the model target. The captured biotin-poly-(KH-Cu)20 polymer could catalyze the oxidation of o-phenylenediamine (OPD) to produce fluorescent 2,3-diaminophenazine (OPDox). The signal was proportional to PSA concentration from 0.01 to 2 ng/mL, and the detection limit was found to be eight pg/mL. The high sensitivity of the method enabled the assays of PSA in real serum samples. The work should be valuable for the design of novel biosensors for clinical diagnosis.

Oxidase-mimicking peptide-copper complexes and their applications in sandwich affinity biosensors

This work reported that the peptide-Cu2+ complexes reveal oxidase-mimicking activities for oxygen reduction and ascorbate oxidation. The peptide features a histidine (His) residue in the first position with respect to the free N-terminal amine. The complexes can be easily integrated with nanomaterials such as gold nanoparticles (AuNPs) to form nanocatalysts or nanozymes, which allows for the fabrication of sensitive sensing platforms. To explore the analytical performances of the peptide-Cu2+ complexes in biosensing, sandwich electrochemical and fluorescent immunoassays of prostate specific antigen (PSA) were performed with AuNP/peptide-Cu2+ conjugates as the nanolabels. In the electrochemical immunoassays, the nanolabels coined as nanocatalysts promoted the electrocatalytic reduction of oxygen. For the fluorescent assays of PSA, the nanolabels coined as nanozymes catalyzed the oxidation of ascorbic acid (AA), and the resulting oxidization product dehydroascorbic acid (DHA) was reacted with o-phenylenediamine (OPD) to form fluorescent 3-(dihydroxyethyl)furo [3,4-b]quinoxaline-1-one (DFQ). The electrochemical and fluorescent signals are proportional to the concentration of PSA in the linear range of 0.001–0.50 and 0.001–2.00 ng/mL, respectively. The low detection limits of the methods (0.40 and 1.00 pg/mL) enabled clinical detection of PSA in serum samples. The findings should be valuable for understanding the biological functions of peptide-Cu2+ complexes, and provide new insight to develop optical and electrochemical sensing platforms for clinical diagnosis.

Synthesis and Application of Albumin Nanoparticles Loaded with Prussian Blue Nanozymes

Prussian blue nanozymes exhibit peroxidase-like catalytic activity and are therefore considered a stable and inexpensive alternative to natural peroxidases in the enzyme-linked immunosorbent assay (ELISA). In this work, we propose a robust method of Prussian blue nanozyme functionalization, which relies on the entrapment of nanozymes into albumin nanoparticles. The principle of the method is the addition of ethanol to a solution that contains albumin and nanozymes. At a high ethanol concentration solubility of albumin decreases, resulting in the formation of albumin nanoparticles loaded with nanozymes. The hydrodynamic diameter of nanoparticles was between 120 and 230 nm and depended on the nanozyme-to-BSA ratio. Encapsulation efficiency of nanozymes reached 96–99% and up to 190 μg of nanozymes were loaded per 1 mg of nanoparticles. Nanoparticles were stable at pH 5.5–7.5 and upon long-term storage in deionized water. Excellent reproducibility of the synthesis procedure was confirmed by the preparation of three individual batches of Prussian-blue-loaded BSA nanoparticles with almost identical properties. Nanoparticles were functionalized with monoclonal antibodies using glutaraldehyde cross-linking. The resulting conjugates were applied as labels in an ELISA-like assay of tumor marker prostate-specific antigen (PSA). The lower limit of detection was below 1 ng/mL, which enables measurement of PSA in the range of clinically relevant concentrations.

The combination of highly efficient resonance energy transfer in one nanocomposite and ferrocene-quenching for ultrasensitive electrochemiluminescence bioanalysis

Sensitive and accurate detection of prostate-specific antigen (PSA) is of great significance since it is regarded as a biomarker for prostate diseases. Herein, a facile strategy for the design of highly efficient electrochemiluminescence (ECL) sensor was proposed for PSA assay. Carboxylated graphitic carbon nitride (g-C3N4) nanosheet (CCN) and tris (2, 2’-Bipyridyl) ruthenium (II) (Ru(bpy)32+) encapsulated in silica nanospheres (RuSi NPs) were employed as the donor and acceptor, respectively. CCN and RuSi NPs were covalently bound within one nanocomposite (CCN@RuSi) through the amide bond, which greatly shortened the electron-transfer path. Thus, the resonance energy transfer (RET) efficiency was remarkably increased, providing a high initial ECL intensity for the ECL assay. After the successive introducing of aptamer, PSA, and ferroceneboronic acid (FcBA) on the surface of CCN@RuSi modified electrode, the ECL signal remarkably decreased, which was caused by the steric hindrance of PSA and electron transfer quenching between Fc+ and excited-state Ru(bpy)32+*. Therefore, a highly efficient ECL platform was constructed, which achieved the ultrasensitive detection of PSA with a linear range and a limit of detection of 100 fg/mL - 50 ng/mL and 1.2 fg/mL, respectively. Furthermore, the dual-affinity of the aptamer and FcBA to PSA endowed the sensor with a high selectivity for the determination of PSA in human serum samples. The present work provides an important reference for the integration of RET and quenching strategy in the ECL study with rapid, ultrasensitive, and highly selective detection performances.

A dual-mode immunosensing strategy for prostate specific antigen detection: Integration of resonance Raman scattering and photoluminescence properties of ZnS:Mn2+ nanoprobes

Luminescence-based methods are widely used for the detection of prostate specific antigen (PSA), for example during the diagnosis of prostate cancer. However, the accuracy of these methods is sub-optimal. The aim of this study was to develop an accurate and sensitive dual-mode immunosensing technique using a combination of resonance Raman scattering (RRS) and photoluminescence (PL) signals for the detection of PSA. A ZnS:Mn2+ nanoprobe was used as the signal reporter, which exhibits both multi-phonon RRS and PL properties. The RRS signal intensity at 348 cm−1 and the PL signal intensity at 590 nm were used for the quantitative assay of PSA. The reproducibility, selectivity and specificity of this dual-mode immunosensing strategy demonstrated an improvement compared with commercial PSA ELISA kits in the analysis of serum samples. Therefore, the RRS-PL immunosensing technique developed in this study shows potential as a reliable technique to be used in the clinical diagnosis of prostate cancer.