A palladium-platinum bimetal nanodendritic melamine network for signal amplification in voltammetric sensing of DNA.

A sandwich-type electrochemical DNA sensor is described for the detection of oligonucleotides typical for MECP2 gene mutations. Palladium nanoparticles (PdNPs) and platinum nanoparticles (PtNPs) were used to synthesize flower-like PdPt nanodendrites (NDs) by a one-pot method. The PdPt NDs possess a high specific surface area and excellent catalytic capabilities. They served as the carrier for the signal DNA probe (SP) and simultaneously catalyze the reduction of hydrogen peroxide (H2O2). The PdPt NDs were modified with melamine, and this results in the formation of a PdPt-melamine network through stable interactions between the PdPt NDs and the three amino groups of each melamine molecule. The network exhibits excellent catalytic ability in enhancing the current signal response in the voltammetric detection of MECP2 gene mutation, best measured at -0.4 V vs. SCE and using H2O2 as the electrochemical probe. In addition, gold nanoflowers were electrodeposited on the electrode interface in order to accelerate electron transfer and to capture the capture probe. The sensor is stable and can detect MECP2 gene mutations in the 1 fmol·L-1 to 1 nmol·L-1 concentration range, with a 0.33 fmol·L-1 lower detection limit at an S/N ratio of 3. Graphical abstract Schematic presentation of electrodes for the determination of the X-linked gene methyl-CpG-binding protein 2 (MECP2). The sensor is based on the electrooxidation of added H2O2 by using the melamine modified palladium platinum bimetal nanodendrites as network signal amplification strategy. This versatile platform expands studies on the detection of monogenic disease.

Sandwich-type biosensor for the detection of α2,3-sialylated glycans based on fullerene-palladium-platinum alloy and 4-mercaptophenylboronic acid nanoparticle hybrids coupled with Au-methylene blue-MAL signal amplification.

α2,3-sialylated glycans (α2,3-sial-Gs) are one of the significant tumour biomarkers for the early diagnosis of cancer. In this work, a neoteric sandwich-type biosensor was developed for detecting α2,3-sial-Gs using 4-mercaptophenylboronic acid (4-MPBA) to construct a novel molecular recognition system by the coordination of a boron atom of 4-MPBA to the amide group of Neu5Ac in the α2,3-sial-Gs structure. Amino-functionalized fullerene coupled with palladium-platinum bimetallic alloy nanocrystals (n-C60-PdPt) was synthesized to modify the surface of a glassy carbon electrode (GCE) because the n-C60 nanomaterial affords a large surface area for the on-site reduction of bimetallic alloy nanoparticles and an excellent capacity for electron transfer. Abundant 4-MPBA were immobilized on the n-C60-PdPt, since the 4-MPBA has the mercapto group can combine with PdPt alloy through strong adsorption. Maackia amurensis lectin (MAL) was covalently immobilized on Au-poly (methylene blue) (Au-PMB) acting as the signal amplification components, which was used to recognize the α2, 3-sial-Gs specifically like a second antibody linked on Au-PMB. The differential pulse voltammetry (DPV) current response of the biosensor in 5mL of PBS (0.1M, pH = 7.4) was recorded, and the proposed sandwich-type biosensor showed a wide linear range of 10 fg mL-1 -100ngmL-1 as well as, a low detection limit of 3fgmL-1 (S/N = 3). Furthermore, the proposed method exhibited good recovery and stability, indicating its potential for use in clinical studies.

PdPt nanoparticles anchored on the N-G with the integration of PANI nanohybrids as novel redox probe and catalyst for the detection of rs1801177.

Single nucleotide polymorphism (SNP) in lipoprotein lipase (LPL) gene (rs1801177) is strongly associated with the increased progression of atherosclerosis, threatening global public health. In this work, a relatively simple, specific and ultrasensitive electrochemical DNA biosensor was constructed to detect rs1801177 for the first time. A glass carbon electrode was modified with fullerene (C60)/polyamidoamine (PAMAM)/gold (Au) nanoparticles nanocomposites film. In addition the nitrogen-doped graphene (N-G)/palladium platinum (PdPt) bimetallic nanoparticle/ polyaniline (PANI) nanohybrids were synthesised and used to label the signal probes. These nanohybrids have abundant active groups, and efficient redox and catalytic activity, allowing them to be used as the nanocarrier for a redox nanoprobe without the additional modification of electroactive substance and catalyst, which could effectively simplify the operation procedure and shorten the analysis time. With the catalysis of H2O2 by nanohybrids, the detection signal of N-G/PdPt/PANI itself could be significantly enhanced, lead to the improvement of the sensitivity. Under optimal conditions, the electrochemical DNA biosensor exhibited desirable performance for the determination of rs1801177 with a wide linearity ranging from 10 fM to 10nM and a relatively low detection limit of 3.33 fM (S/N=3). The proposed biosensor showed excellent selectivity to the target DNA compared to possible interfering substances. The results suggested that this method has potential applications in clinical research.

Target triggered cleavage effect of DNAzyme: Relying on Pd-Pt alloys functionalized Fe-MOFs for amplified detection of Pb2.

We designed an amplified detection strategy for the sensitive determination of lead ions (Pb2+) based on a target-triggered nuclear acid cleavage of Pb2+-specific DNAzyme as a selectivity interface combined with Pd-Pt alloys modified Fe-MOFs (Fe-MOFs/PdPt NPs) hybrids acting as the signal tag. Streptavidin modified reduced graphene oxide-tetraethylene pentamine-gold nanoparticles (rGO-TEPA-Au) served as a sensor platform for immobilizing more DNAzyme. In the presence of Pb2+, the substrate DNA strand can be specifically cleaved at the ribonucleotide site by DNAzyme to produce a new single-DNA on the interface. Then, the hairpin DNA with hybrid strand matched by its complement to the single-DNA was employed to modify the Fe-MOFs/PdPt NPs bioconjugates for signal amplification. Fe-MOFs/PdPt NPs catalyze hydrogen peroxide (H2O2) to produce the electrochemical signal which was recorded by chronoamperometry. Benefiting from the Pb2+-dependent DNAzyme, the proposed method can selectively detect Pb2+ in the presence of other metal ions. The newly designed biosensor exhibited a good linear relationship ranging from 0.005 to 1000nmolL-1 with a low detection limit of 2pM (S/N = 3) for Pb2+. This Pb2+-dependent DNAzyme based ultrasensitive biosensor showed high sensitivity and selectivity, providing potential application for Pb2+ detection in naturally contaminated sewage and spiked drinking water samples.

A sensitive sandwich-type immunosensor for the detection of galectin-3 based on N-GNRs-Fe-MOFs@AuNPs nanocomposites and a novel AuPt-methylene blue nanorod.

We are presenting an electrochemical immunosensor for the determination of Galectin-3 (Gal-3), a biomarker of heart failure. A glassy carbon electrode (GCE) was modified with a film of a composite made from the N-doped graphene nanoribbons immobilized Fe-based-Metal-organic frameworks deposited with Au nanoparticles (N-GNRs-Fe-MOFs@AuNPs). Primary antibody against Gal-3 (Gal-3-Ab1) was immobilized on the Au nanoparticles on the surface of the modified GCE which then was blocked with bovine serum albumin. Signal amplification is crucial for obtaining low detection limits in biosensors. Here, a relatively simple and ultrasensitive sandwich-type electrochemical immunosensor based on novel signal generation and amplification was developed for the determination of Gal-3. A kind of novel redox-active species, AuPt-Methylene blue (MB) (AuPt-MB) nanocomposites, was synthesized by a one-pot method for the first time. Wherein, MB as a kind of the electron transfer mediators in an amperometric biosensor is responsible for electron production and signal amplification. The rod-like AuPt-MB nanohybrids displayed uniform morphology and good electrochemical activity and can combine with the second antibodies against Gal-3 (Gal-3-Ab2). And the AuPt-MB-Ab2 coupled with the N-GNRs-Fe-MOFs@AuNPs-Ab1 to form the sandwich type format that can greatly enhance the biosensor's sensitivity. Under optimal conditions, the designed immunosensor exhibited a linear concentration range from 100fgmL-1 to 50ngmL-1, with a low detection limit of 33.33fgmL-1 (S/N = 3) for Gal-3 in spiked serum. Additionally, the designed immunosensor showed acceptable selectivity, reproducibility and stability. The satisfactory results in analyzing human serum samples indicated potential application promising in monitoring biomarkers.

A dual-type responsive electrochemical immunosensor for quantitative detection of PCSK9 based on n-C60-PdPt/N-GNRs and Pt-poly (methylene blue) nanocomposites.

In this study, a dual-type responsive electrochemical immunosensor was developed for the quantitative detection of proprotein convertase subtilisin/kexin type 9 (PCSK9), a potential biomarker of cardiovascular disease in serum. N-doped graphene nanoribbons (N-GNRs) with good conductivity were used as the sensing matrix modifying the glassy carbon electrode. Palladium platinum alloy (PdPt) nanoparticles with high catalytic performance toward the reduction of hydrogen peroxide (H2O2) were reduced onto amino-functionalized fullerene (n-C60-PdPt) and significantly amplified the electrochemical signal recorded by the amperometric i-t curve. Furthermore, staphylococcus protein A (SPA) with antibody orientation function was introduced to improve the immunoreaction efficiency. Accordingly, a label-free immunosensor was fabricated based on n-C60-PdPt/N-GNRs for the quick detection of PCSK9. Meanwhile, to realize ultrasensitive detection of PCSK9, Pt-poly (methylene blue) (Pt-PMB) nanocomposites synthesized by a one-pot method for the first time were used as a novel signal label, which exhibited uniform morphology as well as good conductivity and produced an electrochemical signal recorded by differential pulse voltammetry (DPV). Herein, a novel sandwich-type immunosensor was designed using n-C60-PdPt/N-GNRs as the sensing matrix and Pt-PMB as the signal label for sensitive detection of PCSK9. Under optimal conditions, the label-free immunosensor showed a linear range of 10pgmL-1 to 100ngmL -1 with a detection limit of 3.33pgmL-1 (S/N=3), and the sandwich-type immunosensor exhibited a linear range of 100 fg mL-1 to 100ngmL -1 with a detection limit of 0.033pgmL-1 (S/N=3) for PCSK9 detection, indicating its potential application in clinical bioassay analysis.

Cerium dioxide-doped carboxyl fullerene as novel nanoprobe and catalyst in electrochemical biosensor for amperometric detection of the CYP2C19*2 allele in human serum.

The disposition dose of clopidogrel is different in CYP2C19*2 gene carriers and non-carriers. High-dose clopidogrel has been recommended to overcome a low-responsiveness to clopidogrel in patients with the CYP2C19*2 gene. To guide the choice of clopidogrel dosage and catalyse a development in the field of personalized therapy, we developed an ultrasensitive electrochemical biosensor to detect CYP2C19*2 gene. We constructed a novel assay based on cerium dioxide (CeO2)-functionalized carboxyl fullerene (c-C60) supported by Pt nanoparticles (c-C60/CeO2/PtNPs) for signal amplification. Au nanoparticles @ Fe-MIL-88NH2 (AuNPs@Fe-MOFs) were synthesized by one-step method as the support platform to enhance the conductivity and immobilize more biotin-modified capture probe (bio-CP) through the superior affinity and specificity between streptavidin and biotin. c-C60/CeO2/PtNPs were labeled with signal probe to form the signal label. After the sandwich reaction of CYP2C19*2 gene between capture probe and the signal label, a distinguishing electrochemical signal from the catalysis of H2O2 by signal label would be observed. Amperometry was applied to record electrochemical signals. Under optimized conditions, the approach showed a good linear dependence between current and the logarithm of CYP2C19*2 gene concentrations in the range of 1 fM to 50nM with a low detection limit of 0.33fM (S/N = 3). The proposed method showed good specificity to target DNA compared with possible interfering substances. More importantly, the fabricated biosensor achieved accurate quantitative detection of CYP2C19*2 gene in human serum samples demonstrated by excellent correlations with standard DNA sequencing and provided a promising strategy for electrochemical biosensor detection of other gene mutations.

Amperometric myeloperoxidase immunoassay based on the use of CuPdPt nanowire networks.

This research describes a nanowire network-based method for detecting the activity of myeloperoxidase (MPO), a biomarker of acute coronary syndromes (ACS). Trimetallic CuPdPt nanowire networks (CuPdPt NWNWs) were prepared by a one-step chemical reduction method. The metallic precursors quickly form nanowire network structures without the need for additional capping agents or surfactants. This process creates a product with a clean surface. The NWNWs were dropped onto a glassy carbon electrode (GCE) to obtain a sensor with good catalytic activity towards the reduction of hydrogen peroxide (H2O2), which was used as an electrochemical probe working at -0.4 V (vs. SCE). It also provided a large surface for further modification. Next, an antibody against MPO was immobilized on the modified GCE via the stable conjunction between Cu, Pt, Pd and amino groups. Upon binding of MPO to the antibody on the GCE, the current response to H2O2 was reduced by 35 µA·cm-2. The immunosensor had a linear response within the 100 fg·mL-1 to 50 ng·mL-1 MPO concentration range and a 33 fg·mL-1 detection limit (at an S/N ratio of 3). The recovery of spiked serum samples ranged from 99.8 to 103.6%. This result suggests that the method can be applied to the quantitation of MPO in human serum samples. Graphical abstract A trimetallic CuPdPt nanowire networks was placed on a glassy cabon electrode (GCE) to design an immunosensor for myeloperoxidase (MPO), a biomarker for the acute coronary syndrome (ACS). Antibody against MPO was immobilized on the network via conjugation between Cu, Pt, Pd and amino groups. Amperometric i-t measurements were conducted to quantify the amount of MPO that binds to the antibody on the surface of the modified GCE.

A new sight for detecting the ADRB1 gene mutation to guide a therapeutic regimen for hypertension based on a CeO2-doped nanoprobe.

The ß1-adrenergic receptor gene (Entrez Gene:ADRB1), as the target of beta-blockers for hypertension, can directly influence the antihypertensive effect of metoprolol in the Chinese population. This therapeutic effect is often hindered by a lack of evidence-based medical information. To address this challenge, we report a novel assay based on graphene oxide and a CeO2 nanocomposite functionalized by 3-aminopropyltriethoxysilane supported Pt nanoparticles (GO/CeO2/PtNPs) as a signal probe. Due to the large specific surface area and good adsorption properties of the GO/CeO2 nanocomposite, large amounts of PtNPs were immobilized, which amplified the electrochemical signal and improved the sensitivity of the biosensor. To further improvement the sensitivity of the biosensor, Streptavidin (SA) was introduced because it can provide more active sites for the immobilization of the biotinylated capture probe (bio-CP). The electrochemical signal was primarily derived from the catalysis of H2O2 by GO/CeO2/PtNPs. Chronoamperometry was applied to record electrochemical signals, which linearly increased with target DNA. Under optimal conditions, the prepared biosensor had a wide linear range from 1fM to 10nM and a low detection limit of 0.33fM in the detecting of ADRB1 gene. Moreover, the proposed method had good stability and recovery, suggesting its potential for use in clinical research.

An impedimetric biosensor for the diagnosis of renal cell carcinoma based on the interaction between 3-aminophenyl boronic acid and sialic acid.

Renal cell carcinoma (RCC) often expresses a high density of sialic acid-rich glycoproteins which helps these late-stage cancer cells to enter the blood stream or urine. Blood diagnosis is a complex and time-consuming process. In this study, we developed a facile and non-invasive electrochemical cytosensor for early detection of RCC in urine samples based on specific recognition by 3-aminophenyl boronic acid (APBA). Polypyrrole (PPy) and bovine serum albumin (BSA)-incorporated Ag submicron particles (Ag@BSA) were co-deposited on a gold electrode (GE) to take advantages of the excellent properties of these biomaterials, including good biocompatibility, low cytotoxicity and excellent electro-conductivity. To further increase the biosensor's sensitivity, APBA molecules were integrated to recognize sialic acid (SA) on the cell surface. Under optimal conditions, the impedimetric cytosensor exhibited a good linear relationship with the logarithm of the cell concentration from 17 to 1.7×106 cellsmL-1, and the low detection limit was 6 cellsmL-1 (S/N=3). Therefore, the electrochemical impedimetric biosensor offers a potential approach to bedside rapid detection of RCC in clinical applications.

A novel non-invasive detection method for the FGFR3 gene mutation in maternal plasma for a fetal achondroplasia diagnosis based on signal amplification by hemin-MOFs/PtNPs.

The small amount of cell-free fetal DNA (cffDNA) can be a useful biomarker for early non-invasive prenatal diagnosis (NIPD) of achondroplasia. In this study, a novel non-invasive electrochemical DNA sensor for ultrasensitive detecting FGFR3 mutation gene, a pathogenic gene of achondroplasia, based on biocatalytic signal materials and the biotin-streptavidin system are presented. Notably encapsulation of hemin in metal-organic frameworks-based materials (hemin-MOFs) and platinum nanoparticles (PtNPs) were used to prepare hemin-MOFs/PtNPs composites via a one-beaker-one-step reduction. We utilized hemin-MOFs/PtNPs for signal amplification because the promising hemin-MOFs/PtNPs nanomaterial has remarkable ability of catalyze H2O2 as well as excellent conductivity. To further amplify the electrochemical signal, reduced graphene oxide-tetraethylene pentamine (rGO-TEPA), gold nanoparticles and streptavidin were selected for modification of the electrode to enhance the conductivity and immobilize more biotin-modified capture probe (Bio-CP) through the high specificity and superior affinity between streptavidin and biotin. The electrochemical signal was primarily derived from the synergistic catalysis of H2O2 by hemin and PtNPs and recorded by Chronoamperometry. Under the optimal conditions, this newly designed biosensor exhibited sensitive detection of FGFR3 from 0.1fM to 1nM with a low detection limit of 0.033fM (S/N=3). We proposed that this ultrasensitive biosensor is useful for the early non-invasive prenatal diagnosis of achondroplasia.

Ultrasensitive electrochemical biosensor based on reduced graphene oxide-tetraethylene pentamine-BMIMPF6 hybrids for the detection of α2,6-sialylated glycans in human serum.

In this paper, a simple, ultrasensitive and label-free electrochemical α2,6-sialylated glycans biosensor based on reduced graphene oxide-tetraethylene pentamine-1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) hybrids was developed. Due to the abundance of amino groups from reduced graphene oxide-tetraethylene pentamine (rGO-TEPA) and the electrostatic interaction of BMIMPF6, bimetallic gold platinum alloy nanoparticles (AuPtNPs) were densely adsorbed onto the surface of the nanocomposite, providing a large surface area available for the immobilization of Sambucus nigra agglutinin (SNA). AuPtNPs have excellent conductivity and catalytic activity, which can promote electron transfer between the electrolyte solution and the surface of electrode and can enhance the sensitivity of biosensor. SNA, which specifically binds α2,6-sialylated glycans, was covalently immobilized on AuPtNPs for specific detection of α2,6-sialylated glycans in human serum. Under optimal experimental conditions, amperometric response changes were used to detect α2,6-sialylated glycans with a broad linear range of 10 fg mL(-1) -1 µg mL(-1) and a low detection limit of 3 fg mL(-1) (S/N=3). When applied to spiked serum samples, the recovery of the developed biosensor ranged from 100.8% to 101.4%, suggesting that the electrochemical biosensor would be suitable for the practical detection of α2,6-sialylated glycans.