Integrated microfluidic systems with an immunosensor modified with carbon nanotubes for detection of prostate specific antigen (PSA) in human serum samples

A Quantitative First Passage Time Model for Tubular Microfluidic Immunoassays

Solid-phase immunosorbent reactions, such as ELISA, are widely used for detecting, identifying, and quantifying protein markers. However, traditional centimeter scale well-based immunoreactors suffer from low surface-to-volume (S/V) ratios, leading to large sample consumption and a long assay time. Microfluidic technologies, particularly tubular microfluidic immunoreactors, have emerged as promising alternatives due to their high S/V ratios. Despite experimental advancements, multifactor theoretical studies on tubular microfluidic systems are limited. In this study, we present a theoretical model based on the first passage time method to analyze diffusion-controlled reaction kinetics in tubular microfluidic immunoreactors. We focus on key parameters including binding kinetics, reactor size, and solution viscosity. To validate the model, controlled laboratory experiments were conducted using our in-house developed tip optofluidic immunoassay (TOI). These experimental results confirmed the reliability of theoretical models in the behavior prediction of tubular microfluidic systems under real-world conditions. Our model revealed that accurate and rapid protein biomarker quantification requires not only the development of microscale bioreactors but also the design of next-generation probes with extraordinary binding affinity and specificity. This work offers insights into optimizing critical design parameters in future microfluidic immunoassay development, paving ways for next generation microliter-sized biomolecular analysis.

Extending the Shelf-Life of Immunoassay-Based Microfluidic Chips through Freeze-Drying Sublimation Techniques

Point-of-care testing (POCT) platforms utilizing immunoassay-based microfluidic chips offer a robust and specific method for detecting target antibodies, demonstrating a wide range of applications in various medical and research settings. Despite their versatility and specificity, the adoption of these immunoassay chips in POCT has been limited by their short shelf-life in liquid environments, attributed to the degradation of immobilized antibodies. This technical limitation presents a barrier, particularly for resource-limited settings where long-term storage and functionality are critical. To address this challenge, we introduce a novel freeze-dry sublimation process aimed at extending the shelf-life of these microfluidic chips without compromising their functional integrity. This study elaborates on the mechanisms by which freeze-drying preserves the bioactivity of the immobilized antibodies, thereby maintaining the chip's performance over an extended period. Our findings reveal significant shelf-life extension, making it possible for these POCT platforms to be more widely adopted and practically applied, especially in settings with limited resources. This research paves the way for more accessible, long-lasting, and effective POCT solutions, breaking down previous barriers to adoption and application.

Enzyme-Linked Immunosorbent Assay: Types and Applications

Enzyme-linked immunosorbent assay (ELISA) is an immunological assay widely used in basic science research, clinical application studies, and diagnostics. The ELISA technique relies on the interaction between the antigen (i.e., the target protein) versus the primary antibody against the antigen of interest. The presence of the antigen is confirmed through the enzyme-linked antibody catalysis of the added substrate, the products of which are either qualitatively detected by visual inspection or quantitatively using readouts from either a luminometer or a spectrophotometer. ELISA techniques are broadly classified into direct, indirect, sandwich, and competitive ELISA-all of which vary based on the antigens, antibodies, substrates, and experimental conditions. Direct ELISA relies on the binding of the enzyme-conjugated primary antibodies to the antigen-coated plates. Indirect ELISA introduces enzyme-linked secondary antibodies specific to the primary antibodies bound to the antigen-coated plates. Competitive ELISA involves a competition between the sample antigen and the plate-coated antigen for the primary antibody, followed by the binding of enzyme-linked secondary antibodies. Sandwich ELISA technique includes a sample antigen introduced to the antibody-precoated plate, followed by sequential binding of detection and enzyme-linked secondary antibodies to the recognition sites on the antigen. This review describes ELISA methodology, the types of ELISA, their advantages and disadvantages, and a listing of some multifaceted applications both in clinical and research settings, including screening for drug use, pregnancy testing, diagnosing disease, detecting biomarkers, blood typing, and detecting SARS-CoV-2 that causes coronavirus disease 2019 (COVID-19).

Numerical Study on a Bio-Inspired Micropillar Array Electrode in a Microfluidic Device

The micropillar array electrode (µAE) has been widely applied in microchip-based electrochemical detection systems due to a large current response. However, it was found that amplifying the current through further adjusting geometrical parameters is generally hindered by the shielding effect. To solve this problem, a bio-inspired micropillar array electrode (bµAE) based on the microfluidic device has been proposed in this study. The inspiration is drawn from the structure of leatherback sea turtles' mouths. By deforming a μAE to rearrange the micropillars on bilateral sides of the microchannel, the contact area between micropillars and analytes increases, and thus the current is substantially improved. A numerical simulation was then used to characterize the electrochemical performance of bµAEs. The effects of geometrical and hydrodynamic parameters on the current of bµAEs were investigated. Moreover, a prototypical microchip integrated with bµAE was fabricated for detailed electrochemical measurement. The chronoamperometry measurements were conducted to verify the theoretical performance of bµAEs, and the results suggest that the experimental data are in good agreement with those of the simulation model. This work presents a novel bµAE with great potential for highly sensitive electrochemical detection and provides a new perspective on the efficient configuration of the µAE.

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.

Recent Progress in Graphene- and Related Carbon-Nanomaterial-based Electrochemical Biosensors for Early Disease Detection

Graphene- and carbon-based nanomaterials are key materials to develop advanced biosensors for the sensitive detection of many biomarkers owing to their unique properties. Biosensors have attracted increasing interest because they allow efficacious, sensitive, selective, rapid, and low-cost diagnosis. Biosensors are analytical devices based on receptors for the process of detection and transducers for response measuring. Biosensors can be based on electrochemical, piezoelectric, thermal, and optical transduction mechanisms. Early virus identification provides critical information about potentially effective and selective therapies, extends the therapeutic window, and thereby reduces morbidity. The sensitivity and selectivity of graphene can be amended via functionalizing it or conjoining it with further materials. Amendment of the optical and electrical features of the hybrid structure by introducing appropriate functional groups or counterparts is especially appealing for quick and easy-to-use virus detection. Various techniques for the electrochemical detection of viruses depending on antigen-antibody interactions or DNA hybridization are discussed in this work, and the reasons behind using graphene and related carbon nanomaterials for the fabrication are presented and discussed. We review the existing state-of-the-art directions of graphene-based classifications for detecting DNA, protein, and hormone biomarkers and summarize the use of the different biosensors to detect several diseases, like cancer, Alzheimer's disease, and diabetes, to sense numerous viruses, including SARS-CoV-2, human immunodeficiency virus, rotavirus, Zika virus, and hepatitis B virus, and to detect the recent pandemic virus COVID-19. The general concepts, mechanisms of action, benefits, and disadvantages of advanced virus biosensors are discussed to afford beneficial evidence of the creation and manufacture of innovative virus biosensors. We emphasize that graphene-based nanomaterials are ideal candidates for electrochemical biosensor engineering due to their special and tunable physicochemical properties.

Prostate cancer and microfluids

Microfluidic systems aim to detect sample matter quickly with high sensitivity and resolution, on a small scale. With its increased use in medicine, the field is showing significant promise in prostate cancer diagnosis and management due, in part, to its ability to offer point-of-care testing. This review highlights some of the research that has been undertaken in respect of prostate cancer and microfluidics. Firstly, this review considers the diagnosis of prostate cancer through use of microfluidic systems and analyses the detection of prostate specific antigen, proteins, and circulating tumor cells to highlight the scope of current advancements. Secondly, this review analyses progressions in the understanding of prostate cancer physiology and considers techniques used to aid treatment of prostate cancer, such as the creation of a micro-environment. Finally, this review highlights potential future roles of microfluidics in assisting prostate cancer, such as in exosomal analysis. In conclusion, this review shows the vast scope and application of microfluidic systems and how these systems will ensure advancements to future prostate cancer management.

The electrochemical detection of prostate specific antigen on glassy carbon electrode modified with combinations of graphene quantum dots, cobalt phthalocyanine and an aptamer

Herein, a novel aptasensor is developed for the electrochemical detection of prostate specific antigen (PSA) on electrode surfaces modified using various combinations of a Cobalt phthalocyanine (CoPc), an aptamer and graphene quantum dots (GQDs). Electrochemical impedance spectroscopy (EIS) as well as differential pulse voltammetry (DPV) are employed for the detection of PSA. In both analytical techniques, linear calibration curves were observed at a concentration range of 1.2-2.0 pM. The glassy carbon electrode where CoPc and GQDs are placed on the electrode when non-covalently linked followed by addition of the aptamer (GQDs-CoPc(ππ)-aptamer (sequential)) showed the best performance with a limit of detection (LoD) as low as 0.66 pM when using DPV. The detection limits were much lower than the dangerous levels reported for PSA in males tested for prostate cancer. This electrode showed selectivity for PSA in the presence of bovine serum albumin, glucose and L-cysteine. The aptasensor showed good stability, reproducibility and repeatability, deeming it a promising early detection device for prostate cancer.

Electrochemical prostate-specific antigen biosensors based on electroconductive nanomaterials and polymers

Prostate cancer (PCa), the second most malignant neoplasm in men, is also the fifth leading cause of cancer-related deaths in men globally. Unfortunately, this malignancy remains largely asymptomatic until late-stage emergence when treatment is limited due to the lack of effective metastatic PCa therapeutics. Due to these limitations, early PCa detection through prostate-specific antigen (PSA) screening has become increasingly important, resulting in a more than 50% decrease in mortality. Conventional assays for PSA detection, such as enzyme-linked immunosorbent assay (ELISA), are labor intensive, relatively expensive, operator-dependent and do not provide adequate sensitivity. Electrochemical biosensors overcome these limitations because they are rapid, cost-effective, simple to use and ultrasensitive. This article reviews electrochemical PSA biosensors using electroconductive nanomaterials such as carbon-, metal-, metal oxide- and peptide-based nanostructures, as well as polymers to significantly improve conductivity and enhance sensitivity. Challenges associated with the development of these devices are discussed thus providing additional insight into their analytic strength as well as their potential use in early PCa detection.

Signal-on electrochemical aptasensors with different target-induced conformations for prostate specific antigen detection

Prostate specific antigen (PSA) has become a potential biomarker for detecting prostate cancer (PCa) in the early stage. Herein, we report a target-induced resolution for the detection of PSA sensitively and specifically by amperometric electrochemical measurements. To meet a satisfactory performance, three conformations of pre-design DNA aptamers including two stem-loop structures and a double strand structure have been investigated and compared. All of them are immobilized on gold electrode as capture probes with redox-active molecular. The mechanism of signal transduction depends on molecular recognition events involving aptamer conformational changes, thus influencing the charge transfer. A short, single-stranded DNA (ssDNA) pseudoknot forming two stem-loop structural aptamers with labeled MB at the 3' -terminus was found to posse the highest signal variation than other structure when induced by PSA due to the strong conformational change. With the optimized capture strand, the aptasensor showed the peak current increase of MB by the binding relationship between PSA and the sensor over a wide concentration range of 4 magnitude orders. The proposed aptasensor exhibited a wide detection range from 10 pg/mL to 500 ng/mL with a low detection limit of 1.24 pg/mL (S/N = 3). Moreover, the electrochemical aptasensor demonstrated good reproducibility, sensitivity, selectivity, and reliability for the detection of PSA. We also found the aptasensor had a good response in the human serum samples, making this device easy to operate for the detection of the PSA physiological concentration.

Highly Selective Optical Sensor Eu (TTA)3 Phen Embedded in Poly Methylmethacrylate for Assessment of Total Prostate Specific Antigen Tumor Marker in Male Serum Suffering Prostate Diseases

A low-cost, simple, and highly selective method was used for the assessment of total prostate specific antigen (tPSA) in the serum of prostate cancer patients. This method is based on quenching the intensity of luminescence displayed by the optical sensor Eu (TTA)₃ phen/poly methylmethacrylate (PMMA) thin membrane or film upon adding different concentrations of tPSA. The luminescent optical sensor was synthesized and characterized through absorption, emission, scanning electron microscopy (SEM), and x-ray diffraction (XRD), and is tailored to present red luminescence at 614 nm upon excitation at 395 nm in water. The fabricated sensor fluorescence intensity is quenched in the presence of tPSA in aqueous media. The fluorescence resonance energy transfer (FRET) is the main mechanism by which the sensor performs. The sensor was successfully utilized to estimate tPSA in the serum of patients suffering prostate cancer in a time and cost effective way. The statistical results of the method were satisfactory with 0.0469 ng mL^-1 as a detection limit and 0.99 as a correlation coefficient.

Polymeric immunosensors for tumor detection

Cancer is a broad-spectrum disease which is spread globally, having high mortality rates. This results from genetic, epigenetic and molecular abnormalities caused by various mutations. The main reason behind this critical problem lies in its diagnostics, the late detection of the disease is the root cause of all this. This can be managed well by the timely diagnosis of cancer by means of the tumor biomarkers present in the body fluids such as serum, blood, and urine. These tumor biomarkers are present in normal conditions as well, but their concentrations are altered in the presence of a malignant tumor. Prolonged studies have reported that immunosensors can be used to detect the minimal amount of biomarkers present in the sample and also provides point-of-care detection. The recent investigations demonstrated the use of polymers along with immunosensors for enhancing their selectivity and sensitivity towards the biomarkers and making them even more efficient. This review focuses on the variety of tumor biomarkers, different types of immunosensors and polymeric immunosensors using different polymers like polypyrrole, polyaniline, PHEMA, etc.

Use of data processing for rapid detection of the prostate-specific antigen biomarker using immunomagnetic sandwich-type sensors

Diagnosis of cancer using electroanalytical methods can be achieved at low cost and in rapid assays, but this may require the combination with data treatment for determining biomarkers in real samples. In this paper, we report an immunomagnetic nanoparticle-based microfluidic sensor (INμ-SPCE) for the amperometric detection of the prostate-specific antigen (PSA) biomarker, the data of which were treated with information visualization methods. The INμ-SPCE consists of eight working electrodes, reference and counter electrodes. On the working electrodes, magnetic nanoparticles with secondary antibodies with the enzyme horseradish peroxidase were immobilized for the indirect detection of PSA in a sandwich-type procedure. Under optimal conditions, the immunosensor could operate within a wide range from 12.5 to 1111 fg·L-1, with a low detection limit of 0.062 fg·L-1. Multidimensional projections combined with feature selection allowed for the distinction of cell lysates with different levels of PSA, in agreement with results from the traditional enzyme-linked immunosorbent assay. The approaches for immunoassays and data processing are generic, and therefore the strategies described here may provide a simple platform for clinical diagnosis of cancers and other types of diseases.

Carbon Nanotubes Modified With Au for Electrochemical Detection of Prostate Specific Antigen: Effect of Au Nanoparticle Size Distribution

Different functionalized Multi-Wall Carbon Nanotube and gold nanoparticles (AuNPs) were synthesized as biosensor electrodes. These materials have been applied to the detection of the Prostate Specific Antigen (PSA). The synthesis of AuNPs was carried out using polyvinylpyrrolidone (PVP) as protecting agent. The PVP/Au molar ratio (0.5 and 50) controls the nanoparticle size distribution, obtaining a wide and narrow distribution with an average diameter of 9.5 and 6.6 nm, respectively. Nanoparticle size distribution shows an important effect in the electrochemical performance of the biosensor, increasing the electrochemical active surface area (EASA) and promoting the electron-transfer from the redox probe (Ferrocene/Ferrocenium) to the electrode. Furthermore, a narrow and small nanoparticle size distribution enhances the amount of antibodies immobilized on the transducer material and the performance during the detection of the PSA. Significant results were obtained for the quantification of PSA, with a limit of detection of 1 ng·ml⁻¹ and sensitivities of 0.085 and 0.056 μA·mL·ng⁻¹ for the two transducer materials in only 5 min of detection.

One-Dimensional Nanostructures: Microfluidic-Based Synthesis, Alignment and Integration towards Functional Sensing Devices

Microfluidic-based synthesis of one-dimensional (1D) nanostructures offers tremendous advantages over bulk approaches e.g., the laminar flow, reduced sample consumption and control of self-assembly of nanostructures. In addition to the synthesis, the integration of 1D nanomaterials into microfluidic chips can enable the development of diverse functional microdevices. 1D nanomaterials have been used in applications such as catalysts, electronic instrumentation and sensors for physical parameters or chemical compounds and biomolecules and hence, can be considered as building blocks. Here, we outline and critically discuss promising strategies for microfluidic-assisted synthesis, alignment and various chemical and biochemical applications of 1D nanostructures. In particular, the use of 1D nanostructures for sensing chemical/biological compounds are reviewed.

A signal-on built in-marker electrochemical aptasensor for human prostate-specific antigen based on a hairbrush-like gold nanostructure

A green electrodeposition method was firstly employed for the synthesis of round hairbrush-like gold nanostructure in the presence of cadaverine as a size and shape directing additive. The nanostructure which comprised of arrays of nanospindles was then applied as a transducer to fabricate a signal-on built in-marker electrochemical aptasensor for the detection of human prostate-specific antigen (PSA). The aptasensor detected PSA with a linear concentration range of 0.125 to 128 ng mL-1 and a limit of detection of 50 pg mL-1. The aptasensor was then successfully applied to detect PSA in the blood serum samples of healthy and patient persons.

Prostate Cancer Stem Cells and Nanotechnology: A Focus on Wnt Signaling

Prostate cancer is the most common cancer among men worldwide. However, current treatments for prostate cancer patients in advanced stage often fail because of relapse. Prostate cancer stem cells (PCSCs) are resistant to most standard therapies, and are considered to be a major mechanism of cancer metastasis and recurrence. In this review, we summarized current understanding of PCSCs and their self-renewal signaling pathways with a specific focus on Wnt signaling. Although multiple Wnt inhibitors have been developed to target PCSCs, their application is still limited by inefficient delivery and toxicity in vivo. Recently, nanotechnology has opened a new avenue for cancer drug delivery, which significantly increases specificity and reduces toxicity. These nanotechnology-based drug delivery methods showed great potential in targeting PCSCs. Here, we summarized current advancement of nanotechnology-based therapeutic strategies for targeting PCSCs and highlighted the challenges and perspectives in designing future therapies to eliminate PCSCs.

Target-triggered signal turn-on detection of prostate specific antigen based on metal-enhanced fluorescence of Ag@SiO2@SiO2-RuBpy composite nanoparticles

A three-layer core-shell nanostructure consisting of a silver core, a silica spacer, and a fluorescent dye RuBpy-doped outer silica layer was fabricated, and the optimal metal-enhanced fluorescence (MEF) distance was explored through adjusting the thickness of the silica spacer. The results show that the optimal distance is ∼10.4 nm with the maximum fluorescence enhancement factor 2.12. Then a new target-triggered MEF 'turn-on' strategy based on the optimized composite nanoparticles was successfully constructed for quantitative detection of prostate specific antigen (PSA), by using RuBpy as the energy donor and BHQ-2 as the acceptor. The hybridization of the complementary DNA of PSA-aptamer immobilized on the surface of the MEF nanoparticles with PSA-aptamer modified with BHQ-2, brought BHQ-2 in close proximity to RuBpy-doped silica shell and resulted in the decrease of fluorescence. In the presence of target PSA molecules, the BHQ-PSA aptamer is dissociated from the surface of the nanoparticles with the fluorescence switched on. Therefore, the assay of PSA was achieved by measuring the varying fluorescence intensity. The results show that PSA can be detected in the range of 1-100 ng ml^-1 with a detection limit of 0.20 ng ml^-1 (6.1 pM), which is 6.7-fold increase of that using hollow RuBpy-doped silica nanoparticles. Moreover, satisfactory results were obtained when PSA was detected in 1% serum.

Diagnostics Strategies with Electrochemical Affinity Biosensors Using Carbon Nanomaterials as Electrode Modifiers

Early diagnosis is often the key to successful patient treatment and survival. The identification of various disease signaling biomarkers which reliably reflect normal and disease states in humans in biological fluids explain the burgeoning research field in developing new methodologies able to determine the target biomarkers in complex biological samples with the required sensitivity and selectivity and in a simple and rapid way. The unique advantages offered by electrochemical sensors together with the availability of high affinity and specific bioreceptors and their great capabilities in terms of sensitivity and stability imparted by nanostructuring the electrode surface with different carbon nanomaterials have led to the development of new electrochemical biosensing strategies that have flourished as interesting alternatives to conventional methodologies for clinical diagnostics. This paper briefly reviews the advantages of using carbon nanostructures and their hybrid nanocomposites as electrode modifiers to construct efficient electrochemical sensing platforms for diagnosis. The review provides an updated overview of some selected examples involving attractive amplification and biosensing approaches which have been applied to the determination of relevant genetic and protein diagnostics biomarkers.

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

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

Label-free electrochemical aptasensing of the human prostate-specific antigen using gold nanospears

Gold nanospears were electrodeposited with the assistance of arginine as a soft template and precise selection of experimental parameters. The nanospears were then employed as a transducer to immobilize an aptamer of prostate-specific antigen (PSA) and fabrication of a label-free electrochemical aptasensor. The aptasensor was employed for the detection of PSA with a linear concentration range of 0.125-200ngmL(-1) and a limit of detection of 50pgmL(-1). The aptasensor was successfully applied to detect PSA in blood serum samples of healthy and patient persons.

Cubic Cu2O nanoframes with a unique edge-truncated structure and a good electrocatalytic activity for immunosensor application

In this work, an ultrasensitive sandwich-type electrochemical immunosensor was developed for the quantitative detection of prostate specific antigen (PSA). Gold nanoparticles decorated 3-aminopropyltriethoxysilane functionalized graphene sheets (Au@APTES-GS) with a large specific surface area, good biocompatibility and superior electron transfer ability were employed as the matrix. In addition, cubic Cu2O nanoframes with hollow edges were employed as the label for the first time. Scanning electron microscope (SEM) images were used to confirm the nanostructure of Au@APTES-GS and Cu2O. Using square wave voltammetry (SWV) to monitor the electrocatalytic process, the signal amplification mechanism of the matrix and the label were explored successfully. Here we find that the unique edge-truncated structure of Cu2O nanoframes can load with a larger amount of redox mediators, ferrocenecarboxylic acid (Fc-COOH), offering a higher electrochemical signal response. Apart from that, Cu2O nanoframes have a good electrocatalytic activity towards the Fc-COOH and hydrogen peroxide (H2O2), making a contribution to further enhance the sensitivity of the fabricated immunosensor. Under optimal conditions, the proposed immunosensor achieved an ultrasensitive and specific detection of PSA, and displayed acceptable reproducibility, selectivity and stability. This work may provide an effective method for the clinical monitoring of tumor markers and demonstrate the potential application promising of nanoframes in the fabrication of immunosensors.

Diagnosis of prostate cancer via nanotechnological approach

Prostate cancer is one of the leading causes of cancer-related deaths among the Caucasian adult males in Europe and the USA. Currently available diagnostic strategies for patients with prostate cancer are invasive and unpleasant and have poor accuracy. Many patients have been overly or underly treated resulting in a controversy regarding the reliability of current conventional diagnostic approaches. This review discusses the state-of-the-art research in the development of novel noninvasive prostate cancer diagnostics using nanotechnology coupled with suggested diagnostic strategies for their clinical implication.

Rapid aptasensor capable of simply diagnosing prostate cancer

Using guanine (G)-rich DNA aptamer-conjugated 6-carboxyfluorescein (6-FAM) capable of rapidly capturing prostate specific antigen (PSA) in human serum, cost-effective and simple biosensor with guanine chemiluminescence detection was developed for early diagnosis of prostate cancer. Free G-rich DNA aptamer-conjugated 6-FAM emits bright light in guanine chemiluminescence reaction based on the principle of chemiluminescent resonance energy transfer (CRET). However, G-rich DNA aptamer-conjugated 6-FAM bound with PSA cannot emit light because PSA acts as a strong interference in CRET between 6-FAM and high-energy intermediate formed from the reaction of 3,4,5-trimethoxylphenylglyoxal (TMPG) and guanine of G-rich DNA aptamer. A chemiluminescent biosensor, developed using the different properties of G-rich DNA aptamer-conjugated 6-FAM in the absence and presence of PSA in guanine chemiluminescence reaction, was able to quantify trace levels of PSA in human serum within 30 min without time-consuming and complicated procedures (e.g., multiple incubation and washings) required for conventional immunoassays operated with expensive and intractable antibodies. The limit of detection of chemiluminescent biosensor having a wide linear dynamic range (1.9-125 ng/ml) was 1.0 ng/ml. The excellent correlation (R=0.985) between chemiluminescent biosensor and conventional enzyme immunoassay indicates that the accurate, precise, and rapid chemiluminescent biosensor can be applied as a new method for early diagnosis of prostate cancer.

Nano-Based PSA Biosensors: An Early Detection Technique of Prostate Cancer

Prostate-specific antigen or PSA is a protein biomarker which is produced by the cells of prostate gland. The normal level of PSA in blood is often elevated in men with prostate cancer. In India, prostate cancer is one among the five, mostly cited cancer in men and it is getting increased by 1% every year. The screening test used for prostate cancer is the Prostate Specific Antigen test. The first PSA assay was determined in 1979. Most of the current techniques used for PSA detection are utilizing large analyzers, there by increased time and cost. Increased PSA levels can also because of prostatitis (inflammation of the prostate gland) or due to many other reasons. A proper technique to differential diagnose this disease is also an issue. The benchmark for the PSA level cannot be determined accurately. For this, various types of biosensors are used. This review journal is is trying to analyze variouus Nano-Biosensors used for early detection of PSA from blood in an early stage itself.

Recent progress in prostate-specific antigen and HIV proteases detection

Proteases mediate a wide variety of biological events and have a critical role in the development of many diseases. Protease detection methods can be hindered by the limitation of assay safety, sensitivity, specificity, time constraints and ease of on-site analysis. Notably, the implementation of various detection methods on biosensing platforms translates them into practical biosensing applications. Currently, the detection of prostate cancer and AIDS at the earliest occasion is one of the major research obstacles. Therefore, recent advances focus on the development of portable detection systems toward point-of-care testing. These detection systems should be highly sensitive and specific for the detection of their prognostic biomarkers, such as the prostate-specific antigen and HIV load assay for prostate cancer and AIDS, respectively. These methods will also facilitate decision-making on a treatment regimen.

Post-genomics nanotechnology is gaining momentum: nanoproteomics and applications in life sciences

The post-genomics era has brought about new Omics biotechnologies, such as proteomics and metabolomics, as well as their novel applications to personal genomics and the quantified self. These advances are now also catalyzing other and newer post-genomics innovations, leading to convergences between Omics and nanotechnology. In this work, we systematically contextualize and exemplify an emerging strand of post-genomics life sciences, namely, nanoproteomics and its applications in health and integrative biological systems. Nanotechnology has been utilized as a complementary component to revolutionize proteomics through different kinds of nanotechnology applications, including nanoporous structures, functionalized nanoparticles, quantum dots, and polymeric nanostructures. Those applications, though still in their infancy, have led to several highly sensitive diagnostics and new methods of drug delivery and targeted therapy for clinical use. The present article differs from previous analyses of nanoproteomics in that it offers an in-depth and comparative evaluation of the attendant biotechnology portfolio and their applications as seen through the lens of post-genomics life sciences and biomedicine. These include: (1) immunosensors for inflammatory, pathogenic, and autoimmune markers for infectious and autoimmune diseases, (2) amplified immunoassays for detection of cancer biomarkers, and (3) methods for targeted therapy and automatically adjusted drug delivery such as in experimental stroke and brain injury studies. As nanoproteomics becomes available both to the clinician at the bedside and the citizens who are increasingly interested in access to novel post-genomics diagnostics through initiatives such as the quantified self, we anticipate further breakthroughs in personalized and targeted medicine.

Carbon nanotubes: properties, synthesis, purification, and medical applications

Current discoveries of different forms of carbon nanostructures have motivated research on their applications in various fields. They hold promise for applications in medicine, gene, and drug delivery areas. Many different production methods for carbon nanotubes (CNTs) have been introduced; functionalization, filling, doping, and chemical modification have been achieved, and characterization, separation, and manipulation of individual CNTs are now possible. Parameters such as structure, surface area, surface charge, size distribution, surface chemistry, and agglomeration state as well as purity of the samples have considerable impact on the reactivity of carbon nanotubes. Otherwise, the strength and flexibility of carbon nanotubes make them of potential use in controlling other nanoscale structures, which suggests they will have a significant role in nanotechnology engineering.

Microfluidic chips for immunoassays

The use of microfluidic chips for immunoassays has been extensively explored in recent years. The combination of immunoassays and microfluidics affords a promising platform for multiple, sensitive, and automatic point-of-care (POC) diagnostics. In this review, we focus on the description of recent achievements in microfluidic chips for immunoassays categorized by their detection method. Following a brief introduction to the basic principles of each detection method, we examine current microfluidic immunosensor detection systems in detail. We also highlight interesting strategies for sensitive immunosensing configurations, multiplexed analysis, and POC diagnostics in microfluidic immunosensors.

Contactless conductivity biosensor in microchip containing folic acid as bioreceptor

We report a glass/PDMS-based microfluidic biosensor that integrates contactless conductivity transduction and folic acid, a target for tumor biomarker, as a bioreceptor. The device presents relevant advantages such as direct determination--dismiss the use of redox mediators as in faradaic electrochemical techniques--and the absence of the known drawbacks related to the electrode-solution interface. Characterizations of the functionalization processes and chemical sensor are described in this communication.

Glass/PDMS hybrid microfluidic device integrating vertically aligned SWCNTs to ultrasensitive electrochemical determinations

This communication reports a promising platform for rapid, simple, direct, and ultrasensitive determination of serotonin. The method is related to integration of vertically aligned single-walled carbon nanotubes (SWCNTs) in electrochemical microfluidic devices. The required microfabrication protocol is simple and fast. In addition, the nanomaterial influenced remarkably the obtained limit-of-detection (LOD) values. Our system achieved a LOD of 0.2 nmol L(-1) for serotonin, to the best of our knowledge one of the lowest values reported in the literature.