An Ultra-Rapid Biosensory Point-of-Care (POC) Assay for Prostate-Specific Antigen (PSA) Detection in Human Serum

Development of a Portable Cell-Based Biosensor for the Ultra-Rapid Screening for Boscalid Residues in Lettuce

Fungal plant pathogens have posed a significant threat to crop production. However, the large-scale application of pesticides is associated with possible risks for human health and the environment. Boscalid is a widely used fungicide, consistently implemented for the management of significant plant pathogens. Conventionally, the detection and determination of boscalid residues is based on chromatographic separations. In the present study, a Bioelectric Recognition Assay (BERA)-based experimental approach combined with MIME technology was used, where changes in the electric properties of the membrane-engineering cells with anti-boscalid antibodies were recorded in response to the presence of boscalid at different concentrations based on the maximum residue level (MRL) for lettuce. The membrane-engineering Vero cells with 0.5 μg/mL of antibody in their surface were selected as the best cell line in combination with the lowest antibody concentration. Furthermore, the biosensor was tested against another fungicide in order to prove its selectivity. Finally, the BERA cell-based biosensor was able to detect the boscalid residue, below and above the MRL, in spiked lettuce leaf extracts in an entirely distinct and reproducible manner. This study indicates that the BERA-based biosensor, after further development and optimization, could be used for the routine, high-throughput detection of boscalid residue in lettuce, and not only that.

Nanomaterials-Based Targeting of Long Non-Coding RNAs in Cancer: A Cutting-Edge Review of Current Trends

This review article spotlights the burgeoning potential of using nanotherapeutic strategies to target long non-coding RNAs (lncRNAs) in cancer cells. This updated discourse underlines the prominent role of lncRNAs in instigating cancer, facilitating its progression, and metastasis, validating lncRNAs' potential for being effective diagnostic biomarkers and therapeutic targets. The manuscript offers an in-depth examination of different strategies presently employed to modulate lncRNA expression and function for therapeutic purposes. Among these strategies, Antisense Oligonucleotides (ASOs), RNA interference (RNAi) technologies, and the innovative clustered regularly interspaced short palindromic repeats (CRISPR)-based gene editing tools garner noteworthy mention. A significant section of the review is dedicated to nanocarriers and their crucial role in drug delivery. These nanocarriers' efficiency in targeting lncRNAs in varied types of cancers is elaborated upon, validating the importance of targeted therapy. The manuscript culminates by reaffirming the promising prospects of targeting lncRNAs to enhance the accuracy of cancer diagnosis and improve treatment efficacy. Consequently, new paths are opened to more research and innovation in employing nanotherapeutic approaches against lncRNAs in cancer cells. Thus, this comprehensive manuscript serves as a valuable resource that underscores the vital role of lncRNAs and the various nano-strategies for targeting them in cancer treatment. Future research should also focus on unraveling the complex regulatory networks involving lncRNAs and identifying fundamental functional interactions to refine therapeutic strategies targeting lncRNAs in cancer.

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.

Electrochemical Biosensors for Whole Blood Analysis: Recent Progress, Challenges, and Future Perspectives

Whole blood, as one of the most significant biological fluids, provides critical information for health management and disease monitoring. Over the past 10 years, advances in nanotechnology, microfluidics, and biomarker research have spurred the development of powerful miniaturized diagnostic systems for whole blood testing toward the goal of disease monitoring and treatment. Among the techniques employed for whole-blood diagnostics, electrochemical biosensors, as known to be rapid, sensitive, capable of miniaturization, reagentless and washing free, become a class of emerging technology to achieve the target detection specifically and directly in complex media, e.g., whole blood or even in the living body. Here we are aiming to provide a comprehensive review to summarize advances over the past decade in the development of electrochemical sensors for whole blood analysis. Further, we address the remaining challenges and opportunities to integrate electrochemical sensing platforms.

An Electrochemical Immunosensor Based on Carboxylated Graphene/SPCE for IgG-SARS-CoV-2 Nucleocapsid Determination

The COVID-19 pandemic has emphasized the importance and urgent need for rapid and accurate diagnostic tests for detecting and screening this infection. Our proposal was to develop a biosensor based on an ELISA immunoassay for monitoring antibodies against SARS-CoV-2 in human serum samples. The nucleocapsid protein (N protein) from SARS-CoV-2 was employed as a specific receptor for the detection of SARS-CoV-2 nucleocapsid immunoglobulin G. N protein was immobilized on the surface of a screen-printed carbon electrode (SPCE) modified with carboxylated graphene (CG). The percentage of IgG-SARS-CoV-2 nucleocapsid present was quantified using a secondary antibody labeled with horseradish peroxidase (HRP) (anti-IgG-HRP) catalyzed using 3,3',5,5'-tetramethylbenzidine (TMB) mediator by chronoamperometry. A linear response was obtained in the range of 1:1000-1:200 v/v in phosphate buffer solution (PBS), and the detection limit calculated was 1:4947 v/v. The chronoamperometric method showed electrical signals directly proportional to antibody concentrations due to antigen-antibody (Ag-Ab) specific and stable binding reaction.

A Novel, Quick, and Reliable Smartphone-Based Method for Serum PSA Quantification: Original Design of a Portable Microfluidic Immunosensor-Based System

Simple Summary

Prostate cancer (PCa) is the most frequently diagnosed malignancy and second most common cause of cancer-related death in males. An early diagnosis is crucial to improve the prognosis. Prostate-Specific Antigen (PSA) is the most widely used biomarker for PCa, but this type of biomarker analysis is performed in centralized laboratories, delaying the diagnosis and initiation of treatment. Our team has developed a miniaturized platform for portable PSA quantification to overcome this shortcoming. It includes a microfluidic chip, immune capture of PSA by magnetic microbeads, and electrochemical quantification. The utilization of a micro-potentiostat allows PSA levels to be read on a smartphone in less than 30 min. This technique was found to offer a fast, easy, specific, sensitive, and reproducible method for PSA quantification. Further research is warranted to verify these findings and explore its potential application at all health care levels.

Abstract

We describe a versatile, portable, and simple platform that includes a microfluidic electrochemical immunosensor for prostate-specific antigen (PSA) detection. It is based on the covalent immobilization of the anti-PSA monoclonal antibody on magnetic microbeads retained in the central channel of a microfluidic device. Image flow cytometry and scanning electron microscopy were used to characterize the magnetic microbeads. A direct sandwich immunoassay (with horseradish peroxidase-conjugated PSA antibody) served to quantify the cancer biomarker in serum samples. The enzymatic product was detected at −100 mV by amperometry on sputtered thin-film electrodes. Electrochemical reaction produced a current proportional to the PSA level, with a linear range from 10 pg mL⁻¹ to 1500 pg mL⁻¹. The sensitivity was demonstrated by a detection limit of 2 pg mL⁻¹ and the reproducibility by a coefficient of variation of 6.16%. The clinical performance of this platform was tested in serum samples from patients with prostate cancer (PCa), observing high specificity and full correlation with gold standard determinations. In conclusion, this analytical platform is a promising tool for measuring PSA levels in patients with PCa, offering a high sensitivity and reduced variability. The small platform size and low cost of this quantitative methodology support its suitability for the fast and sensitive analysis of PSA and other circulating biomarkers in patients. Further research is warranted to verify these findings and explore its potential application at all healthcare levels.

Lateral flow immunoassay based on gold magnetic nanoparticles for the protein quantitative detection: Prostate-specific antigen

Point-of-care testing (POCT) demands for rapidly obtaining test results by means of portable analytical instruments and auxiliary reagents at the sampling site. It's important for tumor marker to be recognized and detected in early clinical diagnosis. Many studies focused on producing small portable devices that would allow fast, accurate, and on-site detection. This study aimed to report a magnetic quantitative lateral flow immunoassay (LFIA) system based on poly (acrylic acid) (PAA)-modified gold magnetic nanoparticles (PGMNs) for detecting prostate-specific antigen (PSA) qualitatively and quantitatively. The result was easily achievable with a portable magnetic reader within 15 min. Under optimal conditions, as low as 0.17 ng/mL PSA could be detected. The method was validated using a well-established Solin electrochemiluminescence immunoassay and showed high consistency in detecting 84 serum samples (R² = 0.98). The quantitative LFIA based on PGMNs established in this study was proven to be rapid, accurate, sensitive, and inexpensive. As a POCT, it can be potentially developed for the quantitative diagnosis of other disease-related protein biomarkers.

A label-free fluorescent aptasensor based on HCR and G-quadruplex DNAzymes for the detection of prostate-specific antigen

Prostate specific antigen (PSA) has been considered as the most potential serological biomarker for the early stage detection of prostate cancer. Here, a label-free fluorescence aptasensing strategy for detecting PSA based on hybridization chain reaction (HCR) and G-quadruplex DNAzymes has been developed. This designed strategy consists of three DNA probes, aptamer probe (AP), hairpin probe 1 (H1) and hairpin probe 2 (H2). In the presence of target PSA, the aptamer sequences in AP specifically recognized PSA to form a PSA-aptamer complex, causing an AP conformation change and thus releasing the initiator, which triggered the chain-like assembly of H1 and H2 that yielded extended nicked double-stranded DNA through HCR. Upon the addition of hemin, the G-rich segments at the end of H1 and H2 self-assembled into the peroxidase-mimicking hemin/G-quadruplex DNAzymes, which catalyzed the hydrogen peroxide-mediated oxidation of thiamine to give a fluorescence signal dependent on the concentration of PSA. Under optimal conditions, a limit of detection of 0.05 nM and a linear range from 0.1 nM to 1 nM (R2 = 0.9942) were achieved by this assay. In addition, other interfering proteins, such as IgG, AFP and CEA, did not produce any significant change in the fluorescence intensity response, indicating good selectivity of this sensor for PSA detection. Finally, this proposed aptasensor was successfully used for diluted serum samples.

Employing an Intercalated Redox Reporter in Electrochemical Aptamer-Based Biosensors to Enable Calibration-Free Molecular Measurements in Undiluted Serum

Electrochemical aptamer-based (E-AB) biosensors suffer from sensor-to-sensor signal variations due to the variation of the total number and the heterogeneity of probes immobilized on the electrode surface, with the former attracting more attention. As such, a calibration process to correct for such variations is required for this type of sensor, causing inconvenience and inaccessibility in harsh sensing environments such as blood samples, which has dramatically limited the widespread clinical use of biosensors. In response, here, we have adopted E-AB sensors to achieve calibration-free measurements of small biological/drug molecules. Specifically, we employ one probe-attached redox reporter and a second intercalated redox reporter to generate two signals, achieving good sensor-to-sensor reproducibility and thus obviating the need for calibration. We first demonstrated the capability of E-AB sensors for the accurate measurement of kanamycin, tobramycin, and adenosine triphosphate (ATP) in phosphate-buffered saline (PBS) buffer, achieving concentration ranges of approximately 4.7 × 10³-, 2.0 × 10³-, and 12.7-fold, respectively. Then, we applied this calibration-free approach to the measurement of these three target molecules directly in undiluted serum, achieving a concentration precision of a few micromolars.

Sensitivity and reproducibility improvements in a human plasma immunoassay with removal of clotting factors

Interferences in human plasma immunoassay are severe challenge that affects the sensitivity and reproducibility of the assay. The clotting factor fibrinogen is a negatively charged protein and is one of the most common sources of interference in immunoassays, and its removal increases the sensitivity and reproducibility. Here, we present a highly sensitive and reproducible method for the detection of prostate specific antigen (PSA) in human plasma immunoassays. Protamine sulfate, a highly positively charged protein, was used to precipitate fibrinogen via ionic interaction to improve the sensitivity and reproducibility of human plasma immunoassay. In a sandwich ELISA for PSA using plasma and protamine-treated plasma samples, the limit of detection was improved from 413 pg/mL in plasma to 235 pg/mL in protamine-treated plasma samples, and the coefficient of variation known as a measure of reproducibility was significantly lowered by protamine treatment. The use of protamine sulfate in human plasma immunoassays for detection of PSA using quartz crystal microbalance (QCM) biosensors resulted in increased sensitivity and reproducibility by about 2-fold and 3-fold, respectively, relative to when not using protamine sulfate. Based on these results, protamine sulfate was the best choice to increase the sensitivity and reproducibility in immunoassays using plasma samples.

Hybridization induced fluorescence enhanced DNA-Ag nanocluster/aptamer probe for detection of prostate-specific antigen

In this work, a label-free Ag nanocluster (AgNC)-based fluorescent probe is proposed to detect tumor marker, prostate-specific antigen (PSA). In the experiments, DNA sequences containing segments complemented to different parts of PSA aptamer were used to synthesize DNA-Ag nanoclusters (DNA-AgNC). Some of the obtained specific DNA-AgNC exhibited significant fluorescence increase after hybridization with PSA aptamer. Based on this, a simple DNA-AgNC/aptamer hybridization probe was fabricated for PSA detection using fluorescence quenching, because competitively specific binding between PSA and its aptamer inhibited the fluorescence enhancement effect of PSA aptamer on DNA-AgNC. The sequence of template DNA, pH and salt concentration of binding buffer, and the concentration of aptamer were optimized. Under optimum conditions, the concentration of PSA within the range of 2-150 ng mL^-1 with the detection limit of 1.14 ng mL^-1 was detected (3σ; n = 7). This approach was also successfully applied to determine PSA in spiked serum samples. As is well known, this was the first report to realize PSA detection using fluorescent AgNC-based probe. This work would provide reference for construction of AgNC-based probes for detecting other proteins.