Amplified Electrochemical Detection of a Cancer Biomarker by Enhanced Precipitation Using Horseradish Peroxidase Attached on Carbon Nanotubes

One-Step Electrochemical Sensing of CA-125 Using Onion Oil-Based Novel Organohydrogels as the Matrices

To reduce the high mortality rates caused by ovarian cancer, creating high-sensitivity, quick, basic, and inexpensive methods for following cancer antigen 125 (CA-125) levels in blood tests is of extraordinary significance. CA-125 is known as the exclusive glycoprotein employed in clinical examinations to monitor and diagnose ovarian cancer and detect its relapses as a tumor marker. Elevated concentrations of this antigen are linked to the occurrence of ovarian cancer. Herein, we designed organohydrogels (ONOHs) for identifying the level of CA-125 antigen at fast and high sensitivity with electrochemical strategies in a serum medium. The ONOH structures are synthesized with glycerol, agar, and glutaraldehyde and at distinct ratios of onion oil, and then, the ONOHs are characterized with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). Electrochemical measurements are performed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) in the absence and presence of CA-125 on the designed ONOHs. For the prepared ONOH-3 electrode, two distinct linear ranges are determined as 0.41-8.3 and 8.3-249.0 U/mL. The limit of quantitation and limit of detection values are calculated as 2.415 and 0.805 μU/mL, respectively, (S/N = 3). These results prove that the developed electrode material has high sensitivity, stability, and selectivity for the detection of the CA-125 antigen. In addition, this study can be reasonable for the practical detection of CA125 in serum, permitting early cancer diagnostics and convenient treatment.

Nanoprecipitation-Enhanced Sensitivity in Enzymatic Nanofluidic Biosensors

Single nanochannels show unique transport properties due to nanoconfinement. It has been demonstrated that at submillimolar concentrations of divalent cations, a nanoprecipitation reaction can occur in nanochannels. Although several reports have shown, described, and modeled the nanoprecipitation process, no further advantages have been taken from this phenomenon. Here, we show that the nanoprecipitation reaction can be incorporated into enzyme-modified nanochannels to enhance the performance of small-molecule biosensors via in situ amplification reactions. Contrary to the working principle of previous enzymatic nanofluidic biosensors, the nanofluidic biosensor described in this work operates on the basis of concerted functions: pH-shifting enzymatic activity and nanoprecipitation. We show that the simple addition of Ca2+ and Mg2+ ions in the working analyte solution containing urea can lower the detection limit from the nanometer to the subnanometer regime and modulate the dynamic linear range. This approach enables the implementation of more sensitive real-time nanofluidic detection methods without increasing the complexity of the nanofluidic platform or the sensing approach. We envision that the integration of concerted functions in nanofluidic architectures will play a key role in expanding the use of these nanoscale devices for analytical purposes.

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.

Advances in nanomaterial-based immunosensors for prostate cancer screening

Prostate cancer is one of the most common health hazards for men worldwide, specifically in Western countries. Rapid prostate cancer screening by analyzing the prostate-specific antigen present in male serum has brought about a sharp decline in the mortality index of this disease. Immunoassay technology quantifies the target analyte in the sample using the antigen-antibody reaction. Immunoassays are now pivotal in disease diagnostics, drug monitoring, and pharmacokinetics. Recently, immunosensors have gained momentum in delivering better results with high specificity and lower limit of detection (LOD). Nanomaterials like gold, silver, and copper exhibit numerous exceptional features and their use in developing immunosensors have garnered excellent results in the diagnostic field. This review highlights the recent and different immunoassay techniques used to detect prostate-specific antigens and discusses the advances in nanomaterial-based immunosensors to detect prostate cancer efficiently. The review also explores the importance of specific biomarkers and nanomaterials-based biosensors with good selectivity and sensitivity to prostate cancer.

Development of electrochemical aptasensors detecting phosphate ions on TMB substrate with epoxy-based mesoporous silica nanoparticles

This study, it is aimed to develop an electrochemical aptasensor that can detect phosphate ions using 3.3'5.5' tetramethylbenzidine (TMB). It is based on the principle of converting the binding affinity of the target molecule phosphate ion (PO₄^3-) into an electrochemical signal with specific aptamer sequences for the aptasensor to be developed. The aptamer structure served as a gate for the TMB to be released and was used to trap the TMB molecule in mesoporous silica nanoparticles (MSNPs). The samples for this study were characterized by transmission electron spectroscopy (TEM), Brunner-Emmet-Teller, dynamic light scattering&electrophoretic light scattering, and induction coupled plasma atomic emission spectroscopy. According to TEM analysis, MSNPs have a morphologically hexagonal structure and an average size of 208 nm. In this study, palladium-carbon nanoparticles (Pd/C NPs) with catalytic reaction were used as an alternative to the biologically used horseradish peroxidase (HRP) enzyme for the release of TMB in the presence of phosphate ions. The limit of detection (LOD) was calculated as 0.983 μM, the limit of determination (LOQ) was calculated as 3.276 μM, and the dynamic linear phosphate range was found to be 50-1000 μM. The most important advantage of this bio-based aptasensor assembly is that it does not contain molecules such as a protein that cannot be stored for a long time at room temperature, so its shelf life is very long compared to similar systems developed with antibodies. The proposed sensor shows good recovery in phosphate ion detection and is considered to have great potential among electrochemical sensors.

Novel electrochemical PMI marker biosensor based on quantum dot dissolution using a double-label strategy

A novel and facile post-mortem interval (PMI) biosensor was fabricated using a double-label strategy to detect the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) biomarker. A monoclonal anti-GAPDH antibody was immobilized on a surface label containing cadmium selenide quantum dots (CdSe QDs) on a cysteamine graphene oxide (Cys-GO) self-assembled monolayer. Glucose oxidase (GOx) was used as a signal label to conjugate with GAPDH. GAPDH recognition was achieved through the dissolution of the surface-attached CdSe QDs by hydrogen peroxide generated through GAPDH-conjugated GOx-catalyzed β-glucose oxidation. To enhance sensitivity, a competitive interaction was introduced between free and conjugated GAPDH to the active site of the anti-GAPDH antibody. The electrochemical response due to CdSe dissolution decreased proportionally with the concentration of free GAPDH. Differential pulsed voltammetry was conducted to determine the analytical characteristics of the immunosensor, including the limit of detection, linear dynamic range, target selectivity, system stability, and applicability toward the analysis of real samples.

A novel affinity peptide-antibody sandwich electrochemical biosensor for PSA based on the signal amplification of MnO2-functionalized covalent organic framework

This work describes a novel affinity peptide-antibody sandwich electrochemical strategy for the ultrasensitive detection of prostate-specific antigen (PSA). Herein, polydopamine-coated boron-doped carbon nitride (Au@PDA@BCN) was synthesized and used as a sensing platform to anchor gold nanoparticles and immobilize primary antibody. Meanwhile, AuPt metallic nanoparticle and manganese dioxide (MnO₂)-functionalized covalent organic frameworks (AuPt@MnO₂@COF) was facilely synthesized to serve as a nanocatalyst and ordered nanopore for the enrichment and amplification of signal molecules (methylene blue, MB). PSA affinity peptide was bound to AuPt@MnO₂@COF to form Pep/MB/AuPt@MnO₂@COF nanocomposites (probe). The peptide-PSA-antibody sandwich biosensor was constructed, and the redox signal of MB was measured with the existence of PSA. The fabricated sensor exhibited a linear response (0.00005-10 ng mL^-1) with a low detection limit of 16.7 fg mL^-1 under the optimum condition. Additionally, the sensor showed an excellent selectivity, ideal repeatability, and good stability for PSA detection in real samples. Furthermore, the porous structure of COF can enrich more MB molecules and increase the sensitivity of the biosensor. This study provides an efficient and ultrasensitive strategy for PSA detection and broadens the use of organic/inorganic porous nanocomposite in biosensing.

High-Sensitivity Dual-Probe Detection of Urinary miR-141 in Cancer Patients via a Modified Screen-Printed Carbon Electrode-Based Electrochemical Biosensor

The screening and diagnosis of cancer are hallmarks of medicine in the aging population. Recently, microRNAs have shown potential for use as biomarkers, which could advance the field of diagnostics. The presence of miRNA-141 in the serum has been well described in several malignancies. However, the invasive approach used for sampling represents the major limitation for its practical application and, hence, its notable absence as a method for screening the general population. In light of this, we aimed to develop a high-sensitivity microRNA (miR) biosensor for application in the diagnosis of all miR-141-associated cancers, such as colorectal cancer (CRC) and breast cancer (BC). The novelty lies in our dual-probe design, which is reliant on the hybridization of the fluorescein isothiocyanate (FITC) targeting probe onto an existing sample of urinary miR-141 in the first step, followed by complementary binding with a biotinylated probe that has been coated on a modified screen-printed carbon electrode (SPCE). The hybridization of the probe and sensor produces signals via the catalytic reduction of H₂O₂ at HRP-modified SPCEs in the presence of H₂O, which was measured by either cyclic voltammetry or chronoamperometry (CA) currents. In our study, the detection and expression of miR-141 in a cohort of colorectal cancer (n = 6) and breast cancer (n = 4) samples showed that its levels were significantly higher than in a healthy cohort (n = 9) (p < 0.004). Moreover, our miR sensor demonstrated high stability, reliability, and sensitivity (p < 0.0001). This work hopefully provides new information for the detection and monitoring of de novo and existing cancers.

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.

An Electrochemical Sensor Based on Chalcogenide Molybdenum Disulfide-Gold-Silver Nanocomposite for Detection of Hydrogen Peroxide Released by Cancer Cells

Hydrogen peroxide (H₂O₂) as a crucial signal molecule plays a vital part in the growth and development of various cells under normal physiological conditions. The development of H₂O₂ sensors has received great research interest because of the importance of H₂O₂ in biological systems and its practical applications in other fields. In this study, a H₂O₂ electrochemical sensor was constructed based on chalcogenide molybdenum disulfide-gold-silver nanocomposite (MoS₂-Au-Ag). Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) were utilized to characterize the nanocomposites, and the electrochemical performances of the obtained sensor were assessed by two electrochemical detection methods: cyclic voltammetry and chronoamperometry. The results showed that the MoS₂-Au-Ag-modified glassy carbon electrode (GCE) has higher sensitivity (405.24 µA mM^-1 cm^-2), wider linear detection range (0.05-20 mM) and satisfactory repeatability and stability. Moreover, the prepared sensor was able to detect the H₂O₂ discharge from living tumor cells. Therefore, this study offers a platform for the early diagnosis of cancer and other applications in the fields of biology and biomedicine.

Electrochemically Controlled ATRP for Cleavage-Based Electrochemical Detection of the Prostate-Specific Antigen at Femtomolar Level Concentrations

As a single-chain glycoprotein with endopeptidase activity, the prostate-specific antigen (PSA) is valuable as an informative serum marker in diagnosing, staging, and prognosis of prostate cancer. In this report, an electrochemical biosensor based on the target-induced cleavage of a specific peptide substrate (PSA peptide) is designed for the highly selective detection of PSA at the femtomolar level, using electrochemically controlled atom transfer radical polymerization (eATRP) as a method for signal amplification. The PSA peptides, without free carboxyl sites, are attached to the gold surface via the N-terminal cysteine residue. The target-induced cleavage of PSA peptides results in the generation of carboxyl sites, to which the alkyl halide initiator α-bromophenylacetic acid (BPAA) is linked via the Zr(IV) linkers. Subsequently, the potentiostatic eATRP of ferrocenylmethyl methacrylate (FcMMA, as the monomer) leads to the surface-initiated grafting of high-density ferrocenyl polymers. As a result, a large amount of Fc redox tags can be recruited for signal amplification, through which the limit of detection (LOD) for PSA can be down to 3.2 fM. As the recognition element, the PSA peptide is easy to synthesize, chemically and thermally stable, and low-cost. Without the necessity of enzyme or nanoparticle labels, the eATRP-based amplification method is easy to operate and low-cost. Results also show that the cleavage-based electrochemical PSA biosensor is highly selective and applicable to PSA detection in complex biological samples. In view of these merits, the integration of the eATRP-based amplification method into cleavage-based recognition is believed to hold great promise for the electrochemical detection of PSA in clinical applications.

Fabrication of a sensitive label free electrochemical immunosensor for detection of prostate specific antigen using functionalized multi-walled carbon nanotubes/polyaniline/AuNPs

The aim of this research is to introduce a novel label free electrochemical immunosensor based on glassy carbon electrode (GCE) modified with carboxylated carbon nanotubes (COOH-MWCNTs)/polyaniline (PANI)/gold nanoparticles (AuNPs) for the detection of prostate specific antigen (PSA). The AuNPs were utilized as a connector for PSA antibody immobilization through NH₂ groups on antibody. Investigations on modified electrode surface were performed by FT-IR spectrum, scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) to evaluate the synthesized nanocomposite and modified electrode surface. As a sensitive analytical method for the detection of PSA, differential pulse voltammetry (DPV) was employed in different ranges of antigen concentration, 1.66 ag·mL^-1 to 1.3 ng·mL^-1. In addition, the detection limit was obtained 0.5 pg·mL^-1, from the linear relationship between antigen concentration log and peak current. Also, the proposed immunosensor was carried out for the determination of PSA in human serum samples, indicating recoveries ranging from 92 to 104%. Finally, it should be noted that the reproducibility and specificity, along with the stability of the present immunosensor were examined, and satisfactory findings were obtained, thus proving it as a promising PSA immunosensor.

A novel label-free colorimetric aptasensor for sensitive determination of PSA biomarker using gold nanoparticles and a cationic polymer in human serum

In this colorimetric assay for sensitive detection of prostate specific antigen (PSA) tumor marker, adsorbed non-thiolated poly-Adenine aptamer (polyA Apt) on the gold nanoparticles (AuNPs) surface was used. By incubating the AuNPs and the PSA specific aptamer prior to target addition, polyA Apt adsorbed on the gold nanoparticles and could bind the target while preventing non-specific interactions. Adsorbed polyA Apt on the AuNPs prevents aggregation of them by poly(diallyldimethylammoniumchloride) (PDDA). Upon the addition of PSA, it bind to the polyA Apt and induce the formation of a secondary structure. Therefore, interaction between polyA Apt and PDDA is repressed and PDDA induce the aggregation of the AuNPs. This analytical platform produces a remarkable optical signal in the absence and presence of PSA that accompanied by a color change from red to blue. This effect as a sensing strategy can be observed with naked eyes and quantified by colorimetry via measurement of the ratio of absorbances at 680 nm and 520 nm. Fabricated aptasensor for detection of PSA is linear in the concentration range of 0.1-100 ng/ml with 20 pg/ml as the limit of detection (S/N = 3). Because of the selectively recognized for PSA in the presence of other interfering substances, this proposed assay applied to real samples for the rapid screening of PSA.

Novel Ce(III)-Metal Organic Framework with a Luminescent Property To Fabricate an Electrochemiluminescence Immunosensor

We designed a novel luminescent metal-organic framework (MOF) named Ce-TCPP-LMOF (CTM) through a simple one-pot solvothermal method. CTM was synthesized by using the emerging electrochemiluminescent (ECL) material (4,4',4″,4‴-(porphine-5,10,15,20-tetrayl)tetrakis(benzoic acid) as the organic ligand and Ce(III) as the metal node. We found that CTM not only has the remarkable ability to emit light but also has a uniform "sandwich biscuit" shape and suitable nanoscale size, which are promising for further applications. We also applied CTM to construct a novel ECL immunosensor and achieve sensitive detection of the proprotein convertase subtilisin/kexin type 9 (PCSK9), a biomarker related to cardiovascular diseases. To further amplify the ECL signal of CTM, a novel dual-amplified signal strategy was established by inducing a polyamidoamine dendrimer (PAMAM) and gold nanoparticles (AuNPs). Importantly, we first proved that the ECL signal of the CTM/S₂O₈^2- system could be enhanced by the PAMAM electric field. As the electron transfer rate was accelerated by the AuNP layer, this ECL signal was further enhanced in AuNP-modified electrodes. The ECL immunosensor showed desirable performance for PCSK9 analysis within a detection range of 50 fg mL^-1 to 10 ng mL^-1 and a low limit of detection of 19.12 ± 2.69 fg mL^-1. Real sample detection suggested that the immunosensor holds great potential for analyzing clinical serum samples.

Enzyme-free amplified SERS immunoassay for the ultrasensitive detection of disease biomarkers

We developed an enzyme-free, amplified SERS immunoassay by combining AgNP-linked immunoreaction and SERS transduction for the ultrasensitive detection of disease biomarkers.

An ethnobotanical study of medicinal plants used to treat skin diseases in northern Pakistan

Background

Skin diseases are a major health concern especially in association with human immune deficiency syndrome and acquired an immune deficiency. The aim of this study was to document the ethnomedicinal information of plants used to treat skin diseases in Northern Pakistan. This is the first quantitative ethnobotanical study of therapeutic herbs utilized by the indigenous people of Northern Pakistan for skin diseases.

Methods

Interviews were taken to obtain information from 180 participants. Quantitative methods including fidelity level (FL), Frequency of citation (FC), Use-value (UV), Jaccard indices (JI), Family importance value (FIV), Relative frequency of citation (RFC) and Chi-square test were applied. Medicinal plants uses are also compared with 50 national and international publications.

Results

In this study, we recorded 106 plant species belonged to 56 floral families for treatment of skin ailments. The dominant life form reported was herb while the preferred method of utilization was powder, along with leaf as the most used plant part. RFC ranges from 0.07 to 0.25% whereas the highest FIV was recorded for family Pteridaceae. FL values range from 36.8 to 100%. The study reported 88% of new plant reports for the treatment of skin diseases.

Conclusion

The present study revealed the importance of several plants used to treat skin diseases by the local communities of Northern Pakistan. The available literature supported the evidence of plant dermatological properties. Plants having high UV and RFC can be considered for further scientific analysis. There is dire need to create awareness among local, government and scientific communities for the preservation of medicinal species and ethnomedicinal knowledge in Northern Pakistan.

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2605-6) contains supplementary material, which is available to authorized users.

An electrochemical immunosensor for the prostate specific antigen based on the use of reduced graphene oxide decorated with gold nanoparticles

The authors describe an immunosensor for the prostate specific antigen (PSA). It was obtained by modifying a glassy carbon electrode (GCE) first modified with gold nanoparticles and then with reduced graphene oxide that was decorated with gold nanoparticles. The AuNPs on reduced graphene oxide provide a suitable surface for attachment of antibodies. On binding of the antigen, the square wave voltammetric signal (measured by using hexacyanoferrate as a probe) reduced. This method has two logarithmically linear analytical ranges that extend from 25 to 55 fg.mL^-1 and from 1 to 36 ng.mL^-1, respectively. The lowest detection limit is 2 pg.mL^-1. Electrochemical impedance spectroscopy was also carried out for PSA determination. EIS works in the 0.0018 to 41 ng.mL^-1 concentration range and has an LOD of 60 pg.mL^-1. This method was applied to the determination of PSA in (spiked) human serum samples. In order to survey the selectivity of immunosensor, determination of PSA was performed in human serum samples, and finally sensitivity and reproducibility were examined. Graphical abstract Facile label free immunosensor based on reduced graphene oxide decorated with gold nanoparticles for early diagnosis prostate cancer via ultrasensitive detection of PSA biomarker: application in human serum.

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.

Sensitive discrimination of single nucleotide variants using a PDA microtube waveguide platform with heterogeneous CHA amplification and competitive inhibition strategy

The CHA system preferentially amplifies the target signal while the competitive system preferentially inhibits the SNV signal using PDA microtubes.

A novel mass spectrometry method based on competitive non-covalent interaction for the detection of biomarkers

We report a novel biosensor platform based on competitive non-covalent interaction between ssDNA and a mass tag towards AuNPs, which detects PSA biomarkers sensitively, observed using MALDI MS. A detection limit of 57 pg mL-1 has been achieved, showing an improvement of two orders of magnitude compared to the traditional spectroscopic method.

Sandwich pair nanobodies, a potential tool for electrochemical immunosensing serum prostate-specific antigen with preferable specificity

Prostate-Specific Antigen (PSA) is a crucial biomarker for screening prostate cancer, but a sensitive and selective immunosensor for rapid quantification of serum PSA remains to be developed. In this study, a sandwich pair of nanobodies (Nbs) (i.e., Nb2 and Nb40) against PSA surface antigen was obtained from an alpaca-derived immune phage display library. A sandwich-type immunosensor for the sensitive and selective detection of PSA in serum samples was ingeniously designed based on the pair of Nbs. The small size of Nb40 allowed high capture densities on the surface of reduced graphene oxide (rGO) nanocomposed with massive Au nanoparticles (rGO@AuNPs), which significantly improved the conductivity and provided a large area to anchor many primary antibodies. The secondary antibody Nb2 fused with streptavidin -binding peptide (SBP) cooperated with Nb40 for PSA sandwiching. Accompanying introduction of horseradish peroxidase-streptavidin (HRP-SA) coupled with Nb2-SBP, the faradaic current was linearly correlated with the logarithm of PSA concentration in a range of 0.1-100 ng mL^-1. More importantly, this immunosensor exhibited excellent selectivity, stability, and reproducibility due to the sandwich pair Nbs. The proposed immunosensor was successfully applied in determining PSA in serum samples and could be used for the sensitive and specific detection of PSA.

Ultrasensitive colorimetric immunoassay for hCG detection based on dual catalysis of Au@Pt core-shell nanoparticle functionalized by horseradish peroxidase

In this paper, an ultrasensitive colorimetric biosensor for human chorionic gonadotrophin (hCG) detection was designed from bottom-up method based on the dual catalysis of the horseradish peroxidase (HRP) and Au@Pt nanoparticles (NPs) relative to H₂O₂-TEM system. HRP and monoclonal mouse anti-hCG antibody (β-submit, mAb₁) were co-immobilized onto the Au@Pt NP surface to improve catalytic efficiency and specificity, which formed a dual functionalized Au@Pt-HRP probe with the mean size of 42.8nm (D₅₀). The colorimetric immunoassay was developed for the hCG detection, and the Au@Pt-HRP probe featured a higher sensitivity in the concentration range of 0.4-12.8IUL^-1 with a low limit of detection (LOD) of 0.1IUL^-1 compared with the LODs of 0.8IUL^-1 for BA-ELISA and of 2.0IUL^-1 for Au@Pt, which indicated that the Au@Pt-HRP probe possessed higher catalytic efficiency with 2.8-fold increase over Au@Pt and 33.8-fold increase over HRP. Also, the Au@Pt-HRP probe exhibited good precision and reproducibility, high specificity and acceptable accuracy with CV being less than 15%. The dual functionalized Au@Pt-HRP probe as a type of signal amplified method was firstly applied in the colorimetric immunoassay for the hCG detection.

Ultrasensitive detection of prostate specific antigen by electrochemical aptasensor using enzyme-free recycling amplification via target-induced catalytic hairpin assembly

Based on the target-induced catalytic hairpin assembly and bimetallic catalyst, the enzyme-free recycling amplification strategy for sensitive detection of prostate specific antigen (PSA) has been designed. The aptamer and its complementary DNA (C-apt) are modified on the magnetic particles. The aptamer-PSA binding event can release the C-apt that triggers the catalytic assembly between hairpin capture DNA and hairpin help DNA. Then the catalytic hairpin assembly leads to cyclic reuse the C-apt and the generation of many opened hairpin capture DNA, which can associate with the prepared Au/Pt-polymethylene blue (PMB) probes to yield electrochemical signal. Meanwhile, the Au/Pt-PMB probes exhibit excellent electrocatalytic ability for H₂O₂ to magnify the response current. The designed sensor possesses a wide dynamic range of 10fgmL^-1 to 100ngmL^-1 and ultra-low detection limit of 2.3fgmL^-1. The present method has good performance in real serum sample analysis. This strategy is promising to be extended to provide a highly sensitive platform for various target analytes.

Nanomaterial-based biosensors for detection of prostate specific antigen

Screening serum for the presence of prostate specific antigen (PSA) belongs to the most common approach for the detection of prostate cancer. This review (with 156 refs.) addresses recent developments in PSA detection based on the use of various kinds of nanomaterials. It starts with an introduction into the field, the significance of testing for PSA, and on current limitations. A first main section treats electrochemical biosensors for PSA, with subsections on methods based on the use of gold electrodes, graphene or graphene-oxide, carbon nanotubes, hybrid nanoparticles, and other types of nanoparticles. It also covers electrochemical methods based on the enzyme-like activity of PSA, on DNA-, aptamer- and biofuel cell-based methods, and on the detection of PSA via its glycan part. The next main section covers optical biosensors, with subsections on methods making use of surface plasmon resonance (SPR), localized SPR and plasmonic ELISA-like schemes. This is followed by subsections on methods based on the use of fiber optics, fluorescence, chemiluminescence, Raman scattering and SERS, electrochemiluminescence and cantilever-based methods. The most sensitive biosensors are the electrochemical ones, with lowest limits of detection (down to attomolar concentrations), followed by mass cantilever sensing and electrochemilumenescent strategies. Optical biosensors show lower performance, but are still more sensitive compared to standard ELISA. The most commonly applied nanomaterials are metal and carbon-based ones and their hybrid composites used for different amplification strategies. The most attractive sensing schemes are summarized in a Table. The review ends with a section on conclusions and perspectives.

Highly sensitive immunosensing of prostate specific antigen using poly cysteine caped by graphene quantum dots and gold nanoparticle: A novel signal amplification strategy

A mediator-free electrochemical immunosensor for quantitation of prostate specific antigen (PSA) based on dual signal amplification strategy was fabricated. In this work, PSA-antibody (anti-PSA) was immobilized onto a green and biocompatible nanocomposite containing poly l-cysteine (P-Cys) as conductive matrix and graphene quantum dots (GQDs)/gold nanoparticles (GNPs) as dual signal amplification elements. Therefore, a novel multilayer film based on P-Cys, GQDs, and GNPs was exploited to develop a highly sensitive amperometric immunosensor for detection of PSA. Fully electrochemical methodology was used to prepare a new transducer on a gold surface which provided a high surface area to immobilize a high amount of the anti-PSA. Importantly, GNPs prepared by soft template synthesized method lead to compact morphology was achieved. The surface morphology of electrode surface was characterized by high-resolution field emission scanning electron microscope (FE-SEM) and energy dispersive spectroscopy (EDX). Chemical compositions of the gold nanoparticles were analysed by an EDX. The immunosensor was employed for the detection of PSA in physiological pH. Under optimized condition the calibration curve for PSA concentration was linear up to 2-9pgmL^-1 with lower limit of quantification of 1.8pgmL^-1.

Recent Progress in Nanomaterial-Based Electrochemical Biosensors for Cancer Biomarkers: A Review

This article reviews recent progress in the development of nanomaterial-based electrochemical biosensors for cancer biomarkers. Because of their high electrical conductivity, high affinity to biomolecules, and high surface area-to-weight ratios, nanomaterials, including metal nanoparticles, carbon nanotubes, and graphene, have been used for fabricating electrochemical biosensors. Electrodes are often coated with nanomaterials to increase the effective surface area of the electrodes and immobilize a large number of biomolecules such as enzymes and antibodies. Alternatively, nanomaterials are used as signaling labels for increasing the output signals of cancer biomarker sensors, in which nanomaterials are conjugated with secondary antibodies and redox compounds. According to this strategy, a variety of biosensors have been developed for detecting cancer biomarkers. Recent studies show that using nanomaterials is highly advantageous in preparing high-performance biosensors for detecting lower levels of cancer biomarkers. This review focuses mainly on the protocols for using nanomaterials to construct cancer biomarker sensors and the performance characteristics of the sensors. Recent trends in the development of cancer biomarker sensors are discussed according to the nanomaterials used.

Nanomaterials for Electrochemical Immunosensing

Electrochemical immunosensors resulting from a combination of the traditional immunoassay approach with modern biosensors and electrochemical analysis constitute a current research hotspot. They exhibit both the high selectivity characteristics of immunoassays and the high sensitivity of electrochemical analysis, along with other merits such as small volume, convenience, low cost, simple preparation, and real-time on-line detection, and have been widely used in the fields of environmental monitoring, medical clinical trials and food analysis. Notably, the rapid development of nanotechnology and the wide application of nanomaterials have provided new opportunities for the development of high-performance electrochemical immunosensors. Various nanomaterials with different properties can effectively solve issues such as the immobilization of biological recognition molecules, enrichment and concentration of trace analytes, and signal detection and amplification to further enhance the stability and sensitivity of the electrochemical immunoassay procedure. This review introduces the working principles and development of electrochemical immunosensors based on different signals, along with new achievements and progress related to electrochemical immunosensors in various fields. The importance of various types of nanomaterials for improving the performance of electrochemical immunosensor is also reviewed to provide a theoretical basis and guidance for the further development and application of nanomaterials in electrochemical immunosensors.