Analytical performance of the Roche total and free PSA assays on the Elecsys 2010 immunoanalyzer

Evaluation of Plasma Circulating Cell Free DNA Concentration and Integrity in Patients with Prostate Cancer in Jamaica: A Preliminary Study

Background: Cell free circulating DNA (cfcDNA) is a promising diagnostic tool for prostate cancer (PCa). This study aimed to measure the cfcDNA concentration and integrity in PCa patients using quantitative polymerase chain reaction (qPCR) analysis. This study also assessed the correlation between these molecular biomarkers with total prostate-specific antigen (PSA), Gleason score, prostate volume, and age. Methods: Eleven PCa patients and 9 persons with benign prostatic hyperplasia (BPH) were recruited. Blood samples were collected before prostate biopsy and plasma quantified by qPCR amplification of the ALU 115 DNA sequence, with the ratio of ALU 247 to ALU 115 reflecting cfcDNA integrity. Results: There were no significant differences in median, interquartile range (IQR) cfcDNA concentration or cfcDNA integrity between the patients with PCa (47.9 (214.93) ng/mL; 0.61 (0.49)) and persons with BPH (41.5 (55.13) ng/mL, p = 0.382; 0.67 (0.45), p = 0.342). A weakly positive correlation exists between cfcDNA concentration and total PSA (r = 0.200, p = 0.555) but not with age or Gleason score in PCa patients. Conclusion: cfcDNA concentration was relatively nonsignificantly higher in PCa patients in comparison to persons with BPH, whereas cfcDNA integrity was similar in both groups. Though limited in sample size, this study shows that cfcDNA concentration may be a potentially valuable noninvasive biomarker for the diagnosis of PCa.

Investigation on core-fucosylated prostate-specific antigen as a refined biomarker for differentiation of benign prostate hyperplasia and prostate cancer of different aggressiveness

Prostate cancer represents a major cause of cancer death in men worldwide. Novel non-invasive methods are still required for differentiation of non-aggressive from aggressive tumors. Recently, changes in prostate-specific antigen glycosylation pattern, such as core-fucosylation, have been described in prostate cancer. The objective of this study was to evaluate whether the core-fucosylation determinant of serum prostate-specific antigen may serve as refined marker for differentiation between benign prostate hyperplasia and prostate cancer or identification of aggressive prostate cancer. A previously developed liquid chromatography-mass spectrometry/mass spectrometry-based strategy was used for multiplex analysis of core-fucosylated prostate-specific antigen (fuc-PSA) and total prostate-specific antigen levels in sera from 50 benign prostate hyperplasia and 100 prostate cancer patients of different aggressiveness (Gleason scores, 5-10) covering the critical gray area (2-10 ng/mL). For identification of aggressive prostate cancer, the ratio of fuc-PSA to total prostate-specific antigen (%-fuc-PSA) yielded a 5%-8% increase in the area under the curve (0.60) compared to the currently used total prostate-specific antigen (area under the curve = 0.52) and %-free prostate-specific antigen (area under the curve = 0.55) tests. However, our data showed that aggressive prostate cancer (Gleason score > 6) and non-aggressive prostate cancer (Gleason score ≤ 6) could not significantly (p-value = 0.08) be differentiated by usage of %-fuc-PSA. In addition, both non-standardized fuc-PSA and standardized %-fuc-PSA had no diagnostic value for differentiation of benign prostate hyperplasia from prostate cancer. The %-fuc-PSA serum levels could not improve the differentiation of non-aggressive and aggressive prostate cancer compared to conventional diagnostic prostate cancer markers. Still, it is unclear whether these limitations come from the biomarker, the used patient cohort, or the imprecision of the applied method itself. Therefore, %-fuc-PSA should be further investigated, especially by more precise methods whether it could be clinically used in prostate cancer diagnosis.

Analysis of urinary PSA glycosylation is not indicative of high-risk prostate cancer

The levels of core fucosylation and α2,3-linked sialic acid in serum Prostate Specific Antigen (PSA), using the lectins Pholiota squarrosa lectin (PhoSL) and Sambucus nigra agglutinin (SNA), can discriminate between Benign Prostatic Hyperplasia (BPH) and indolent prostate cancer (PCa) from aggressive PCa. In the present work we evaluated whether these glycosylation determinants could also be altered in urinary PSA obtained after digital rectal examination (DRE) and could also be useful for diagnosis determinations. For this purpose, α2,6-sialic acid and α1,6-fucose levels of urinary PSA from 53 patients, 18 biopsy-negative and 35 PCa patients of different aggressiveness degree, were analyzed by sandwich ELLA (Enzyme Linked Lectin Assay) using PhoSL and SNA. Changes in the levels of specific glycosylation determinants, that in serum PSA samples were indicative of PCa aggressiveness, were not found in PSA from DRE urine samples. Although urine is a simpler matrix for analyzing PSA glycosylation compared to serum, an immunopurification step was necessary to specifically detect the glycans on the PSA molecule. Those specific glycosylation determinants on urinary PSA were however not useful to improve PCa diagnosis. This could be probably due to the low proportion of PSA from the tumor in urine samples, which precludes the identification of aberrantly glycosylated PSA.

Microfluidic Immuno-Biochip for Detection of Breast Cancer Biomarkers Using Hierarchical Composite of Porous Graphene and Titanium Dioxide Nanofibers

We report on a label-free microfluidic immunosensor with femtomolar sensitivity and high selectivity for early detection of epidermal growth factor receptor 2 (EGFR2 or ErbB2) proteins. This sensor utilizes a uniquely structured immunoelectrode made of porous hierarchical graphene foam (GF) modified with electrospun carbon-doped titanium dioxide nanofibers (nTiO2) as an electrochemical working electrode. Due to excellent biocompatibility, intrinsic surface defects, high reaction kinetics, and good stability for proteins, anatase nTiO2 are ideal for electrochemical sensor applications. The three-dimensional and porous features of GF allow nTiO2 to penetrate and attach to the surface of the GF by physical adsorption. Combining GF with functional nTiO2 yields high charge transfer resistance, large surface area, and porous access to the sensing surface by the analyte, resulting in new possibilities for the development of electrochemical immunosensors. Here, the enabling of EDC-NHS chemistry covalently immobilized the antibody of ErbB2 (anti-ErbB2) on the GF-nTiO2 composite. To obtain a compact sensor architecture, the composite working electrode was designed to hang above the gold counter electrode in a microfluidic channel. The sensor underwent differential pulse voltammetry and electrochemical impedance spectroscopy to quantify breast cancer biomarkers. The two methods had high sensitivities of 0.585 μA μM(-1) cm(-2) and 43.7 kΩ μM(-1) cm(-2) in a wide concentration range of target ErbB2 antigen from 1 × 10(-15) M (1.0 fM) to 0.1 × 10(-6) M (0.1 μM) and from 1 × 10(-13) M (0.1 pM) to 0.1 × 10(-6) M (0.1 μM), respectively. Utilization of the specific recognition element, i.e., anti-ErbB2, results in high specificity, even in the presence of identical members of the EGFR family of receptor tyrosine kinases, such as ErbB3 and ErbB4. Many promising applications in the field of electrochemical detection of chemical and biological species will derive from the integration of the porous GF-nTiO2 composite into microfluidic devices.

Improvement of Prostate Cancer Diagnosis by Detecting PSA Glycosylation-Specific Changes

New markers based on PSA isoforms have recently been developed to improve prostate cancer (PCa) diagnosis. However, novel approaches are still required to differentiate aggressive from non-aggressive PCa to improve decision making for patients.

PSA glycoforms have been shown to be differentially expressed in PCa. In particular, changes in the extent of core fucosylation and sialylation of PSA N-glycans in PCa patients compared to healthy controls or BPH patients have been reported. The objective of this study was to determine these specific glycan structures in serum PSA to analyze their potential value as markers for discriminating between BPH and PCa of different aggressiveness.

In the present work, we have established two methodologies to analyze the core fucosylation and the sialic acid linkage of PSA N-glycans in serum samples from BPH (29) and PCa (44) patients with different degrees of aggressiveness. We detected a significant decrease in the core fucose and an increase in the α2,3-sialic acid percentage of PSA in high-risk PCa that differentiated BPH and low-risk PCa from high-risk PCa patients. In particular, a cut-off value of 0.86 of the PSA core fucose ratio, could distinguish high-risk PCa patients from BPH with 90% sensitivity and 95% specificity, with an AUC of 0.94. In the case of the α2,3-sialic acid percentage of PSA, the cut-off value of 30% discriminated between high-risk PCa and the group of BPH, low-, and intermediate-risk PCa with a sensitivity and specificity of 85.7% and 95.5%, respectively, with an AUC of 0.97. The latter marker exhibited high performance in differentiating between aggressive and non-aggressive PCa and has the potential for translational application in the clinic.

Analytical performance of the VITROS® Immunodiagnostic Products total PSA II and free PSA assays

OBJECTIVES

To assess the precision and the performance of the VITROS(®) total PSA II (tPSA) and free PSA (fPSA) assays on the VITROS(®) ECi/ECiQ Immunodiagnostic system.

DESIGN AND METHODS

The precision of the tPSA and fPSA assays was evaluated following the Clinical and Laboratory Standards Institute (CLSI)-guideline EP5-A2. During a 20-day period, 2 runs of 5 quality control (QC) samples were performed daily. Results of tPSA (n=292) and fPSA (n=289) were compared between VITROS(®) ECi/ECiQ Immunodiagnostic system and Roche Cobas 8000 e602 system (Cobas tPSA and fPSA assays). A modified CLSI-guideline EP9-A2 was used to correlate the results based on a Deming regression correlation study.

RESULTS

A within-run and within-calibration imprecision of ≤2% was obtained for all 5 QC concentration levels for both tPSA and fPSA. Method comparison revealed a constant bias of 17% for tPSA and 6% for fPSA. These values are within the desirable bias of 18.7% suggested by the Westgard Biological Variation Database Specifications. A high agreement was found between the two methods, with correlation coefficients of 0.997 and 0.993 for tPSA and fPSA respectively.

CONCLUSION

The VITROS(®) tPSA and fPSA assays showed an excellent precision and bias and a good correlation with the Roche method.

Microfluidic electrochemical immunoarray for ultrasensitive detection of two cancer biomarker proteins in serum

A microfluidic electrochemical immunoassay system for multiplexed detection of protein cancer biomarkers was fabricated using a molded polydimethylsiloxane channel and routine machined parts interfaced with a pump and sample injector. Using off-line capture of analytes by heavily-enzyme-labeled 1 μm superparamagnetic particle (MP)-antibody bioconjugates and capture antibodies attached to an 8-electrode measuring chip, simultaneous detection of cancer biomarker proteins prostate specific antigen (PSA) and interleukin-6 (IL-6) in serum was achieved at sub-pg mL⁻¹ levels. MPs were conjugated with ∼90,000 antibodies and ∼200,000 horseradish peroxidase (HRP) labels to provide efficient off-line capture and high sensitivity. Measuring electrodes feature a layer of 5 nm glutathione-decorated gold nanoparticles to attach antibodies that capture MP-analyte bioconjugates. Detection limits of 0.23 pg mL⁻¹ for PSA and 0.30 pg mL⁻¹ for IL-6 were obtained in diluted serum mixtures. PSA and IL-6 biomarkers were measured in serum of prostate cancer patients in total assay time 1.15 h and sensor array results gave excellent correlation with standard enzyme-linked immunosorbent assays (ELISA). These microfluidic immunosensors employing nanostructured surfaces and off-line analyte capture with heavily labeled paramagnetic particles hold great promise for accurate, sensitive multiplexed detection of diagnostic cancer biomarkers.

Single-wall carbon nanotube forest arrays for immunoelectrochemical measurement of four protein biomarkers for prostate cancer

Protein arrays that measure multiple protein cancer biomarkers in clinical samples hold great promise for reliable early cancer detection. Herein, we report a prototype 4-unit electrochemical immunoarray based on single-wall carbon nanotube forests for the simultaneous detection of multiple protein biomarkers for prostate cancer. Immunoarray procedures were designed to measure prostate specific antigen (PSA), prostate specific membrane antigen (PSMA), platelet factor-4 (PF-4), and interleukin-6 (IL-6) simultaneously in a single serum sample. All of these proteins are elevated in serum of patients with prostate cancer, but they have widely different relative levels of serum concentration. Horseradish peroxidase (HRP) was used as label on detection (secondary) antibodies in a sandwich immunoassay scheme. Biotinylated secondary antibodies (Ab(2)) that bind specifically to streptavidin-HRP conjugates provided 14-16 labels per antibody and gave the necessary higher sensitivity required for PF-4 and IL-6 detection at physiological levels. Conventional singly labeled Ab(2)-HRP conjugates were sufficient for PSA and PSMA detection. Immunoarrays were used to measure four biomarkers in clinical human serum samples of prostate cancer patients and controls with excellent correlation to referee enzyme-linked immunosorbent (ELISA) assays.

Carbon nanotube amplification strategies for highly sensitive immunodetection of cancer biomarkers

We describe herein the combination of electrochemical immunosensors using single-wall carbon nanotube (SWNT) forest platforms with multi-label secondary antibody-nanotube bioconjugates for highly sensitive detection of a cancer biomarker in serum and tissue lysates. Greatly amplified sensitivity was attained by using bioconjugates featuring horseradish peroxidase (HRP) labels and secondary antibodies (Ab(2)) linked to carbon nanotubes (CNT) at high HRP/Ab(2) ratio. This approach provided a detection limit of 4 pg mL(-)(1) (100 amol mL(-)(1)), for prostate specific antigen (PSA) in 10 microL of undiluted calf serum, a mass detection limit of 40 fg. Accurate detection of PSA in human serum samples was demonstrated by comparison to standard ELISA assays. PSA was quantitatively measured in prostate tissue samples for which PSA could not be differentiated by the gold standard immunohistochemical staining method. These easily fabricated SWNT immunosensors show excellent promise for clinical screening of cancer biomarkers and point-of-care diagnostics.

Engineering Camel Single-Domain Antibodies and Immobilization Chemistry for Human Prostate-Specific Antigen Sensing

The specificity and affinity characteristics of antibodies make them excellent probes in biosensor applications. Unfortunately, their large size, unstable behavior, and random immobilization properties create numerous problems. The single-domain antigen-binding fragment derived from heavy-chain antibodies of camelids (termed VHH) offers special advantages in terms of size, stability, and ease of generating different antibody constructs. In this study, we show the potential of those VHHs in sensing human prostate-specific antigen (hPSA) by SPR technology. Different VHH constructs were immobilized onto commercial and custom-built sensor surfaces by metal chelation, biotin-streptavidin interaction, or covalent coupling. The detection of subnanogram per milliliter hPSA concentrations could be attained on a covalently coupled three-dimensional dextran surface. Moreover, the ratio of different hPSA isoform concentrations could be assessed via a sandwich assay and resulted in the detection of clinically significant antigen concentrations within 15 min. In addition, for the first time, the intrinsic protein stability is presented as an important probe design factor, since our results reveal that higher intrinsic stability offers higher resistance to harsh regeneration conditions. In conclusion, we present VHHs as a novel class of biosensor probes rivaling conventional antibodies and their derived antibody fragments.