Biomarker Prostate Specific Antigen Research Articles

Magnetic microbead-based upconversion immunoassay with laser-induced breakdown spectroscopy readout for the detection of prostate-specific antigen.

Laser-induced breakdown spectroscopy (LIBS) is a promising technique for the readout of immunochemical assays utilizing indirect detection of labels (Tag-LIBS), typically based on nanoparticles. We have previously demonstrated that Tag-LIBS immunoassay employing yttrium-based photon-upconversion nanoparticles (UCNPs) can reach sensitivity similar to commonly used enzyme and fluorescence immunoassays. In this study, we report on further increasing the sensitivity of UCNP-based Tag-LIBS immunoassay by employing magnetic microbeads (MBs) as the solid phase in the determinationof cancer biomarker prostate-specific antigen. Due to the possibility of analyte preconcentration, MBs enabled achieving a limit of detection (LOD) of 4.0pg·mL-1, representing two orders of magnitude improvement compared withequivalent microtiter plate-based assay (LOD of 460pg·mL-1). In addition, utilizing MBs opens up the possibility of an internal standardization of the LIBS readout by employing iron spectral lines, which improves the assay robustness by compensating for LIBS signal fluctuations and bead-bound immunocomplexes lost throughout the washing steps. Finally, the practical applicability of the technique was confirmed by the successful analysis of clinical samples, showing a strong correlation with the standard electrochemiluminescence immunoassay. Overall, MB-based Tag-LIBS was confirmed as a promising immunoassay approach, combining fast readout, multiplexing possibilities, and high sensitivity approaching upconversion luminescence scanning while avoiding the requirement of luminescence properties of labels.

Carbon dots functionalized polyaniline as efficient sensing platform for cancer biomarker detection

Implementing simple and rapid detection of cancer biomarker using biosensors has the potential to contribute greatly to basic biological research and early detection of cancer. Tailoring of biosensor matrix based on conducting polymers has gained significant attention in recent years due to its electroactivity, redox property and biocompatibility. Herein, biomass derived carbon dots (CDs) were anchored on polyaniline (PANI) surface to get biocompatible and fluorescent, carbon dots functionalized polyaniline (CDs@PANI) that enable binding of large amount of prostate cancer biomarker, prostate specific antigen (PSA) antibody on its surface via active functional groups. Immobilization efficiency of CDs@PANI was investigated by electrochemical methods which revealed dense immobilization of biomolecules on CDs@PANI as compared to conventional PANI. A sandwich electrochemical biosensor was constructed using CDs@PANI as immobilization matrix for detection of prostate cancer biomarker PSA. The sensor displayed good sensitivity, specificity, stability, reproducibility, wide linear range (0.01–60 ng/ml) and a low detection limit of 20 pg/ml. The importance of CDs in improving the sensor performance was demonstrated by carrying out detailed electrochemical studies using glucose oxidase as a model biomolecule. Biocompatibility of sensing matrix was assessed by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay for cell viability using WI26 cells. The sensing platform demonstrated herein provides great potential for the detection of different cancer biomarkers and metabolites.

Ultrasensitive detection of prostate-specific antigen using a SERS-based magnetic immunosensor

Concentrations of disease biomarkers and their changes are crucial for the diagnosis and monitoring of diseases, so detecting and capturing small changes in biomarkers is especially important. This study demonstrates a surface-enhanced Raman scattering (SERS)-active magnetic immunosensor using a signal amplification strategy for the ultrasensitive detection of prostate-specific antigen (PSA). The sensor consists of a biotin-modified aptamer (B-Apt) and a PSA antibody (Ab) labeled on magnetic beads (MBs), which can immobilize and anchor the target PSA when it is present. After sequential addition of streptavidin and a signal probe, the generated streptavidin-biotin complex reacts to form a three-dimensional network, thereby increasing the number of signal molecules to achieve signal amplification, with the detection limit of 0.87 pg/mL. In addition, this method was also performed to detect PSA in human serum samples. It is believed that this method provides a more sensitive tool for detecting PSA or other biomarkers in clinical samples.

Portable and Rapid Dual-Biomarker Detection Using Solution-Gated Graphene Field Transistors in the Accurate Diagnosis of Prostate Cancer.

Prostate-specific antigen (PSA) is the common serum-relevant biomarker for early prostate cancer (PCa) detection in clinical diagnosis. However, it is difficult to accurately diagnose PCa in the early stage due to the low specificity of PSA. Herein, a new solution-gated graphene field transistor (SGGT) biosensor with dual-gate for dual-biomarker detection is designed. The sensing mechanism is that the designed aptamers immobilized on the surface of the gate electrodes can capture PSA and sarcosine (SAR) biomolecules and induce the capacitance changes of the electric double layers of SGGT. The limit of detections of PSA and SAR biomarkers can reach 0.01 fg mL-1 , which is three-to-four orders of magnitude lower than previously reported assays. The detection time of PSA and SAR is ≈4.5 and ≈13 min, which is significantly faster than the detection time (1-2h) of conventional methods. The clinical serum samples testing demonstrates that the biosensor can distinguish the PCa patients from the control group and the diagnosis accuracy can reach 100%. The SGGT biosensor can be integrated into the portable platform and the diagnostic results can directly display on the smartphone/Pad. Therefore, the integrated portable platform of the biosensor can distinguish cancer types through the dual-biomarker detection.

A multispectroscopic approach for ultra-trace sensing of prostate specific antigen (PSA) by iron nanocomposite fabricated on graphene nanoplatelet

Herein we report an easy, rapid and cost-effective method for spectroscopic sensing of a prostate cancer biomarker prostate specific antigen (PSA) using a novel nanocomposite. The material is a synthetic quinoxaline derivative-based iron nanocomposite fabricated on graphene nanoplatelet surface (1d-Fe-Gr). Presence of graphene enhanced the efficacy of synthesized 1d-Fe-Gr to sense PSA in serum medium with an impressive limit of detection (LOD) value of 0.878 pg/mL compared to 1d-Fe alone (LOD 17.619 pg/mL) using UV–visible absorption spectroscopy. LOD of PSA by 1d-Fe-Gr using Raman spectroscopy is even more impressive (0.410 pg/mL). Moreover, presence of interfering biomolecules like glucose, cholesterol, bilirubin and insulin in serum improves the detection threshold significantly in presence of 1d-Fe-Gr which otherwise cause LOD values of PSA to elevate in control sets. In presence of these biomolecules, the LOD values improve significantly as compared to healthy conditions in the range 0.623–3.499 pg/mL. Thus, this proposed detection method could also be applied efficiently to the patients suffering from different pathophysiological disorders. These biomolecules may also be added externally during analyses to improve the sensing ability. Fluorescence, Raman and circular dichroism spectroscopy were used to study the underlying mechanism of PSA sensing by 1d-Fe-Gr. Molecular docking studies confirm the selective interaction of 1d-Fe-Gr with PSA over other cancer biomarkers.

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.

Chitosan/luminol/AgNPs nanocomposite for electrochemiluminescent determination of prostate-specific antigen.

Agreen, environmentally friendly protocol was developed for ultrasensitive and highly specific recognition of prostate-specific antigen (PSA) based on the ECL effect of luminol supported by chitosan-silver nanoparticles (CS/AgNPs) nanocomposites. The transducing surface was fabricated through two consecutive electrodeposition steps of gold nanoparticles (AuNPs) and chitosan (CS)-AgNPs-luminol electrochemiluminophore onto the glassy carbon electrode. In addition to anappropriate desirable biocompatibility, theelectrochemical synthesis presents low-cost preparation and ultrafast determination opportunity. AgNPs play a linking role to attach luminol, as an ECL agent to the CS support via donor-acceptor bonds between Ag atoms with NH groups of luminol and CS. Also, AgNPs can amplify the ECL intensity as a consequence of their excellent specific surface area and conductivity. To enhance the performance of the nanobiosensor, AuNPs were also used due totheir high-specific surface area and excellent affinity toward amine groups of CS. Based on this high-performance analysis strategy, ultrasensitive screening of PSA was attained with a desirable limit of detection of 0.6 ng mL-1 and a broad linear range between 1 pg mL-1 and 10 ng⋅mL-1 (R2=0.994). Approximately, the same results were recorded for the analysis of the unprocessed serum samples of patients with prostate cancer at different stages. This research provided significant insight into electrografting methods to construct ECL transducers for clinical monitoring of PSA and other tumor biomarkers in the clinical setting.

Unamplified and Real-Time Label-Free miRNA-21 Detection Using Solution-Gated Graphene Transistors in Prostate Cancer Diagnosis.

The incidence of prostate cancer (PCa) in men globally increases as the standard of living improves. Blood serum biomarker prostate-specific antigen (PSA) detection is the gold standard assay that do not meet the requirements of early detection. Herein, a solution-gated graphene transistor (SGGT) biosensor for the ultrasensitive and rapid quantification detection of the early prostate cancer-relevant biomarker, miRNA-21 is reported. The designed single-stranded DNA (ssDNA) probes immobilized on the Au gate can hybridize effectively with the miRNA-21 molecules targets and induce the Dirac voltage shifts of SGGT transfer curves. The limit of detection (LOD) of the sensor can reach 10-20 M without amplification and any chemical or biological labeling. The detection linear range is from 10-20 to 10-12 M. The sensor can realize real-time detection of the miRNA-21 molecules in less than 5 min and can well distinguish one-mismatched miRNA-21 molecule. The blood serum samples from the patients without RNA extraction and amplification are measured. The results demonstrated that the biosensor can well distinguish the cancer patients from the control group and has higher sensitivity (100%) than PSA detection (58.3%). Contrastingly, it can be found that the PSA level is not directly related to PCa.

Influence of Label and Solid Support on the Performance of Heterogeneous Immunoassays.

Conventional immunochemical methods used in clinical analysis are often not sensitive enough for early-stage diagnosis, resulting in the need for novel assay formats. Here, we provide a detailed comparison of the effect of different labels and solid supports on the performance of heterogeneous immunoassays. When comparing three types of streptavidin-modified labels─horseradish peroxidase, carboxyfluorescein, and photon-upconversion nanoparticles (UCNPs)─UCNPs led to the most sensitive and robust detection of the cancer biomarker prostate-specific antigen. Additionally, we compared the immunoassay formats based on conventional microtiter plates and magnetic microbeads (MBs). In both cases, the highest signal-to-background ratios and the lowest limits of detection (LODs) were obtained by using the UCNP labels. The MB-based upconversion-linked immunosorbent assay carried out with a preconcentration step provided the lowest LOD of 0.46 pg/mL in serum. The results demonstrate that the use of UCNPs and MBs can significantly improve the sensitivity and working range of heterogeneous immunoassays for biomarker detection.

Serum CCL2 Is a Prognostic Biomarker for Non-Metastatic Castration-Sensitive Prostate Cancer.

Purpose: Prostate-specific antigen (PSA) is a useful prostate cancer (PC) biomarker, but some cases reported that PSA does not correlate with the Gleason score. Serum chemokine (CC motif) ligand 2 (CCL2) has been reported to be a potential complementary PSA biomarker, but it remains unclear whether it can be applied to non-metastatic castration-sensitive prostate cancer (nmCSPC) or each section of the stages. Serum CCL2′s usefulness was investigated as a prognostic nmCSPC biomarker in this study. Methods: Serum samples were collected from 379 patients who underwent prostate biopsy at Kanazawa University Hospital from 2007 to 2013. A total of 230 patients with nmCSPC were included in this study of the 255 patients with histologically diagnosed prostate cancer. The serum CCL2 efficacy as a prognostic nmCSPC biomarker was investigated retrospectively. Results: An independent significant predictor of worse OS was CCL2 ≥ 280 pg/dL and CRP ≥ 0.5 mg/dL in multivariate analysis. Gleason score ≥ 8 and CCL2 ≥ 280 pg/dL were independent significant predictors of CRPC-free survival (CFS) worsening in multivariate analysis. Serum CCL2 was a predictive biomarker for OS and CFS in nmCSPC. Furthermore, CCL2 ≥ 280 pg/mL patients had significantly worse visceral metastasis-free survival than those with CCL2 < 280 pg/mL. Conclusion: This study is the first to demonstrate serum CCL2 utility as a biomarker to predict OS and CFS in nmCSPC.

Detection of prostate cancer biomarkers via a SERS-based aptasensor

The overexpression of specific biomarkers in serum is closely related to diseases, and accurate and sensitive detection of them is beneficial for the early diagnosis and treatment of cancer. In this study, we developed a novel surface-enhanced Raman spectroscopy (SERS)-based aptasensor to detect the prostate-specific antigen biomarkers, consisting of total prostate-specific antigen (PSA) and free prostate-specific antigen (f-PSA). A composite structure containing arrays of polystyrene colloidal sphere @Ag shell (PS@Ag) was fabricated as a SERS-active chip. A complementary DNA probe (SH-DNA) and PSA aptamer (Apt) were immobilised stepwise on the chip, followed by the binding of a Raman reporter methylene blue (MB) to the guanine base of the aptamer. PSA-Apt recognition causes the release of MB-Apt and a decrease in the SERS intensity of MB on the chip, which correlates with the PSA concentration. The proposed biosensor has high spectral reproducibility, selectivity, and sensitivity and successfully determines the PSA levels in serum samples collected from prostate cancer patients, demonstrating great potential for clinical diagnosis.

Sensitive recognition of prostate-specific antigen using biotinylated antibody encapsulated on D-penicillamine decorated wrinkled silicate nanoparticles (WSN): An innovative sandwich-type biosensor toward diagnosis of prostate cancer.

In this study, a new sandwich-type biosensor was developed to specific recognition of prostate-specific antigen (PSA) and early-stage diagnosis of prostate cancer using encapsulation of biotinylated antibody (Ab1) of prostate-specific antigen on D-penicillamine decorated wrinkled silicate nanoparticles (WSN). For the first time, KCC-1-NH-DPA was synthesized and used to immobilization of biomacromolecules. So, fabricated immunosensor was performed by on sandwich-type strategy. After fabrication of immunosensor, cyclic voltammetry, differential pulse voltammetry, and square wave voltammetry techniques were used to electrochemical evaluation of immune-platform for PSA detection. The proposed biocompatibility immune-platform provided a novel interface toward sensitive bioanalysis of PSA biomarker in human plasma samples. Due to the use of gold nanoparticles functionalized Cysteamine (Cys A) in the structure of the secondary antibody (Ab2 [HRP-Ab2]), the intensity of the electrochemical signal has increased, resulting in a more accurate detection of the target molecules. Under the right conditions, the engineering immunosensor provides good bioanalytical performance for determining the PSA biomarker in the linear range of 0.002 to 60 μg L-1 which low limit of quantification was 0.002 μg L-1 . As a result, it is suggested to use these immune-devices in the clinical pre-diagnosis of prostate cancer.

Biocompatible Osmium Telluride-Polypyrrole Nanocomposite Material: Application in Prostate Specific Antigen Immunosensing

Prostate cancer is a dominant global threat to society. It affects nearly 4000 men in South Africa annually, making it the second most threatening cancerous disease after lung cancer. A potential serological biomarker to monitor early diagnosis of prostate cancer is prostate specific antigen (PSA). We used the PSA biomarker in our work to develop an extremely sensitive electrochemical immunosensor to achieve low detection limits. The fabrication steps followed with the combination of thioglycolic acid capped osmium telluride quantum dots (TGA-OsTe2QD)-polypyrrole (PPy) nanocomposite and prostate specific antigen modified on a glassy carbon electrode. The UV-Vis signatures of TGA-OsTe2QD-PPy showed an absorption band at 262 nm which is attributed to the PPy and TGA-OsTe2QD composite. This band corresponds to the energy band gap of 4.4 and 5.4 eV. The CV responses of BSA|Ab|TGA-OsTe2QD|PPy|GCE modified electrode to prostate specific antigen (PSA) was studied within a range of 0–16 ng/mL PSA that was linear, herein referred to as liner range (LR), which produced a limit of detection (LOD) value of 0.36 ng/mL PSA. The values of the immunosensor’s calibration parameters (LR and LOD) make them suitable for real sample application, due to their coverage of the PSA concentration range (0–14 ng/mL) that is of clinical importance.

Clinical Relevance of Circulating Tumor Cells in Prostate Cancer Management.

Given the low specificity of the routinely used biomarker prostate-specific antigen, circulating tumor cell (CTC) enumeration seems to be particularly useful in the monitoring of prostate cancer. In this review, we focused on a few aspects of CTC enumeration in prostate malignancies: prognostic value in metastatic and non-metastatic tumors, role in the monitoring of treatment outcomes, use as a surrogate marker for survival, and other applications, mostly for research purposes. CTC enumeration, without a doubt, offers an attractive perspective in the management of prostate cancer. However, the vast majority of available data about the role of CTC in this malignancy originate from randomized studies of anticancer agents and do not necessarily translate into real-world clinical practice. Further, most studies on the application of CTC in prostate cancer patients were limited to advanced stages of this malignancy. Meanwhile, the role of CTC in the early stages of prostate cancer, in which some patients may present with occult disseminated disease, is still relatively poorly understood, and should thus be studied extensively. Other obstacles in the widespread application of CTC enumeration in routine clinical practice include considerable discrepancies in the number of cells determined with various commercially available systems.

An Innovative Immunoanalysis Strategy towards Sensitive Recognition of PSA Biomarker in Human Plasma Samples Using Flexible and Portable Paper Based Biosensor: A New Platform towards POC Detection of Cancer Biomarkers Using Integration of Pen-on Paper Technology with Immunoassays Methods

Background: The prostate-specific antigen (PSA) is one of the best markers for detecting prostate cancer. Rapid and real time recognition of PSA biomarker could be helpful in the early diagnosis and efficient treatment of prostate cancer. One of the usual methods to identify this biomarker is ELISA, which has a picomolar detection range but requires specialized personnel and also this technique is time-consuming and expensive. Methods: Cost-effective POC devices are great solutions because they are very cost-effective, sensitive and simple, do not require expert operators and have a high response time in a short time. With that in mind, in this work, a novel and simple label-free paper-based electrochemical immunosensor were designed by using conductive Ag-ink and designed directly by pen on paper technique on the surface of photographic paper, which is a suitable substrate for antibody immobilization, for rapid detection of PSA. Results: Based on the obtained results, under the optimum conditions, the synthesized Ag ink has a great substrate for antibody (Ab) and antigen (Ag) immobilization. The linear range was from 0.001 to 30 μg/L and the obtained low limite of quantification (LLOQ) was 0.001μg/L. This immunosensor also tested in human plasma samples, which had good analytical power. Conclusion: The proposed paper-based immunoassay could be a hopefully new and cheap tool for the diagnosis of other biomarkers.

Biomarkers in Prostate Cancer Diagnosis: From Current Knowledge to the Role of Metabolomics and Exosomes.

Early detection of prostate cancer (PC) is largely carried out using assessment of prostate-specific antigen (PSA) level; yet it cannot reliably discriminate between benign pathologies and clinically significant forms of PC. To overcome the current limitations of PSA, new urinary and serum biomarkers have been developed in recent years. Although several biomarkers have been explored in various scenarios and patient settings, to date, specific guidelines with a high level of evidence on the use of these markers are lacking. Recent advances in metabolomic, genomics, and proteomics have made new potential biomarkers available. A number of studies focused on the characterization of the specific PC metabolic phenotype using different experimental approaches has been recently reported; yet, to date, research on metabolomic application for PC has focused on a small group of metabolites that have been known to be related to the prostate gland. Exosomes are extracellular vesicles that are secreted from all mammalian cells and virtually detected in all bio-fluids, thus allowing their use as tumor biomarkers. Thanks to a general improvement of the technical equipment to analyze exosomes, we are able to obtain reliable quantitative and qualitative information useful for clinical application. Although some pilot clinical investigations have proposed potential PC biomarkers, data are still preliminary and non-conclusive.

Elevated Expression of Glycerol-3-Phosphate Phosphatase as a Biomarker of Poor Prognosis and Aggressive Prostate Cancer.

Simple SummaryA number of diseases, including cancers, can be diagnosed with “biomarkers”, such as specific proteins, hormones, or mutations in some genes. These molecules reflect abnormal processes in the affected organs, and are useful for diagnosis and disease treatment options. The need exists to have reliable markers for various types of cancers such as prostate cancer (PC). Many cancers show high utilization of glucose for their growth; we recently identified an enzyme, glycerol 3-phosphate phosphatase (G3PP), that can modulate glucose utilization by cells. Our work revealed a high expression of G3PP in prostate cancer cells in patients with aggressive tumors. With further validation, G3PP expression in prostate cancer tumors may become a useful prognostic biomarker and aid in the management of patients with PC.The limitations of the biomarker prostate-specific antigen (PSA) necessitate the pursuit of biomarkers capable of better identifying high-risk prostate cancer (PC) patients in order to improve their therapeutic management and outcomes. Aggressive prostate tumors characteristically exhibit high rates of glycolysis and lipogenesis. Glycerol 3-phosphate phosphatase (G3PP), also known as phosphoglycolate phosphatase (PGP), is a recently identified mammalian enzyme, shown to play a role in the regulation of glucose metabolism, lipogenesis, lipolysis, and cellular nutrient-excess detoxification. We hypothesized that G3PP may relieve metabolic stress in cancer cells and assessed the association of its expression with PC patient prognosis. Using immunohistochemical staining, we assessed the epithelial expression of G3PP in two different radical prostatectomy (RP) cohorts with a total of 1797 patients, for whom information on biochemical recurrence (BCR), metastasis, and mortality was available. The association between biomarker expression, biochemical recurrence (BCR), bone metastasis, and prostate cancer-specific survival was established using log-rank and multivariable Cox regression analyses. High expression of G3PP in PC epithelial cells is associated with an increased risk of BCR, bone metastasis, and PC-specific mortality. Multivariate analysis revealed high G3PP expression in tumors as an independent predictor of BCR and bone metastasis development. High G3PP expression in tumors from patients eligible for prostatectomies is a new and independent prognostic biomarker of poor prognosis and aggressive PC for recurrence, bone metastasis, and mortality.

One-photon excited photoluminescence of gold nanospheres and its application in prostate specific antigen detection via fluorescence correlation spectroscopy (FCS)

Gold nanoparticles are known to exhibit appealing intrinsic plasmon-modulated photoluminescence (PL) properties which can be explored in various fluorescence-based sensing applications. In this paper, we evaluate the PL of different-sized gold nanospheres (AuNSs) under one-photon excitation (1PE) and develop a sensitive homogeneous immunoassay for the detection of prostate specific antigen (PSA) in colloidal suspension via fluorescence correlation spectroscopy (FCS). The 1PE PL of AuNSs of three different sizes are evaluated in solution phase under excitation at 405 nm via steady-state fluorescence spectroscopy measurements, while FCS analysis emphasizes the feasibility of using 1PE PL properties to monitor their diffusion behavior. Fluorescence lifetime imaging microscopy (FLIM) assays coupled with PL spectral profile analysis performed on single-particles-like structures conform the plasmonic origin of the detected PL and validate their potential of synthesized AuNSs as fluorescent probes in bioimaging and bioassays. Finally, to the best of our knowledge, we provide the first demonstration of the successful use of the 1PE PL of the synthesized AuNSs as probes for the FCS-based one-step label-free sensitive optical detection of PSA biomarker. The approach consisting in monitoring the diffusion of the AuNSs-oligomers induced by the interaction of anti-PSA-conjugated AuNSs with PSA molecules is successfully validated for the detection of PSA levels as low as 4.4 ng/ml in solution. Considering that the development of rapid, efficient and label-free biosensing methods is of continuous interest nowadays, we are confident that our results may have a strong impact on medicine towards more efficient, sensitive and reliable diagnosis.

Prostate-Specific antigen: An overview and its current status in the diagnosis of prostate cancer

Prostate-Specific Antigen (PSA), which has high organ specificity and poor cancer specificity, has been widely utilized for the diagnosis and treatment of prostate cancer; though it is not an ideal tumor marker. Its extensive usage in screening programs has resulted in a large number of unwanted biopsies, over-diagnosis and over-treatment of indolent cancers as well. Hence, various PSA derivatives and PSA-based tests have evolved to improve the accuracy of prostate cancer diagnosis. This article provides an overview of PSA and PSA-based biomarkers and their current role in the screening and diagnosis of prostate cancer.

Enzyme-Free Colorimetric Immunoassay for Protein Biomarker Enabled by Loading and Disassembly Behaviors of Polydopamine Nanoparticles

In this work, a mussel-inspired polydopamine (PDA) nanoparticle with biocompatible and reactive surface characteristics was desirably incorporated with high loading capacity and pH-induced disassembly-releasing behavior toward Fe(III) ions to develop an enzyme-free colorimetric immunoassay. The catechol functional network of PDA can act as a scaffold to coordinate with large amounts of Fe(III) ions to form the PDA-Fe(III) NPs whose coordination state can be tailored by changing the pH values. In detail, PDA-Fe(III) NPs can be maintained in a disassembled tri-coordinate state under alkaline conditions while the highly loaded Fe(III) ions can be easily released under acid conditions to react with ferrocyanide for the in situ generation of Prussian blue (PB) NPs. The detection sensitivity of prostate-specific antigen (PSA) was significantly improved, owing to the high peroxidase-like activity of PB NPs that triggered excellent catalytic effect by the colorimetric reaction. In addition, favorable linearity was found in the range of 0.0005-20 ng mL-1 with a low detection limit of 0.84 pg mL-1 (S/N = 3). Furthermore, excellent selectivity and reproducibility were exhibited by the developed enzyme-free colorimetric immunoassay. It is believed that this proposed PDA-Fe(III) NP-based enzyme-free colorimetric system will offer a facile and reliable tool for the sensitive detection of PSA and other cancer biomarkers in human serum.