Nonenzymatic Electrochemical Detection of Glucose Based on Palladium−Single-Walled Carbon Nanotube Hybrid Nanostructures

Enzyme-labeled Pt@BSA nanocomposite as a facile electrochemical biosensing interface for sensitive glucose determination

Electrocatalytic reactions of glucose oxidation based on enzyme-labeled electrochemical biosensors demand a high enzymatic activity and fast electron transfer property to produce the amplified signal response. Through a "green" synthesis method, Pt@BSA nanocomposite was prepared as a biosensing interface for the first time. Herein we presented a convenient and effective glucose sensing matrix based on Pt@BSA nanocomposite along with the covalent adsorption of glucose oxidase (GOD). The electrocatalytic activity toward oxygen reduction was significantly enhanced due to the excellent bioactivity of anchored GOD and superior catalytic performance of interior platinum nanoparticles, which was gradually restrained with the addition of glucose. A sensitive glucose biosensor was then successfully developed upon the restrained oxygen reduction peak current. Differential pulse voltammetry (DPV) was employed to investigate the determination performance of the enzyme biosensor, resulting in a linear response range from 0.05 to 12.05 mM with an optimal detection limit of 0.015 mM. The as-proposed sensing technique revealed high selectivity against endogenous interfering species, satisfactory storage stability, acceptable durability, and favorable fabrication reproducibility with the RSD of 3.8%. During the practical application in human blood serum samples, this glucose biosensor obtained a good detection accuracy of analytical recoveries within 97.5 to 104.0%, providing an alternative scheme for glucose level assay in clinical application.

Porous platinum nanotubes labeled with hemin/G-quadruplex based electrochemical aptasensor for sensitive thrombin analysis via the cascade signal amplification

For the first time, a sensitive electrochemical aptasensor for thrombin (TB) was developed by using porous platinum nanotubes (PtNTs) labeled with hemin/G-quadruplex and glucose dehydrogenase (GDH) as labels. Porous PtNTs with large surface area exhibited the peroxidase-like activity. Coupling with GDH and hemin/G-quadruplex as NADH oxidase and HRP-mimicking DNAzyme, the cascade signal amplification was achieved by the following ways: in the presence of glucose and NAD(+) in the working buffer, GDH electrocatalyzed the oxidation of glucose with the production of NADH. Then, hemin/G-quadruplex as NADH oxidase catalyzed the oxidation of NADH to in situ generate H2O2. Based on the corporate electrocatalysis of PtNTs and hemin/G-quadruplex toward H2O2, the electrochemical signal was significantly amplified, allowing the detection limit of TB down to 0.15 pM level. Moreover, the proposed strategy was simple because the intercalated hemin offered the readout signal, avoiding the adding of additional redox mediator as signal donator. Such an electrochemical aptasensor is highly promising for sensitive detection of other proteins in clinical diagnostics.

Mesoporous Ni0.3Co2.7O4 hierarchical structures for effective non-enzymatic glucose detection

An electrode modified with mesoporous Ni_0.3Co_2.7O₄ hierarchical structures shows a low detection limit of 1.0 μM glucose, good sensitivity of 206.5 mA mM⁻¹ cm⁻², and good selectivity.

Facile fabrication of CuO nanowire modified Cu electrode for non-enzymatic glucose detection with enhanced sensitivity

A facile method to fabricate a non-enzymatic glucose sensor based on CuO nanowires is developed.

Shape and size control of Cu nanoparticles by tailoring the surface morphologies of TiN-coated electrodes for biosensing applications

A method for controlling the shapes and sizes of Cu nanoparticles during electrodeposition has been developed by tailoring the surface morphologies of TiN-coated electrodes. Larger octahedral Cu NPs grew on a granular TiN film; smaller, irregular Cu NPs formed on a pyramidal TiN film. The surface morphology of the TiN film affected the accumulation of Cu(2+) and hexadecyltrimethylammonium (CTA(+)) ions, leading to the different shapes and sizes of the resulting Cu NPs. The significant steric effect of the CTA(+) ions was confirmed when using the film of pyramidal TiN as the electrode in the CTAB-containing electrolyte; it contributed to the growth of the smaller, irregular Cu NPs. The sensitivity of the smaller, irregular Cu NPs in the detection of glucose was better than that of the larger, octahedral Cu NPs because of the former's greater increase in the Cu(2+)-to-Cu(0) ratio.

Synthesis of palladium/helical carbon nanofiber hybrid nanostructures and their application for hydrogen peroxide and glucose detection

We report on a novel sensing platform for H2O2 and glucose based on immobilization of palladium-helical carbon nanofiber (Pd-HCNF) hybrid nanostructures and glucose oxidase (GOx) with Nafion on a glassy carbon electrode (GCE). HCNFs were synthesized by a chemical vapor deposition process on a C60-supported Pd catalyst. Pd-HCNF nanocomposites were prepared by a one-step reduction free method in dimethylformamide (DMF). The prepared materials were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. The Nafion/Pd-HCNF/GCE sensor exhibits excellent electrocatalytic sensitivity toward H2O2 (315 mA M(-1) cm(-2)) as probed by cyclic voltammetry (CV) and chronoamperometry. We show that Pd-HCNF-modified electrodes significantly reduce the overpotential and enhance the electron transfer rate. A linear range from 5.0 μM to 2.1 mM with a detection limit of 3.0 μM (based on the S/N = 3) and good reproducibility were obtained. Furthermore, a sensing platform for glucose was prepared by immobilizing the Pd-HCNFs and glucose oxidase (GOx) with Nafion on a glassy carbon electrode. The resulting biosensor exhibits a good response to glucose with a wide linear range (0.06-6.0 mM) with a detection limit of 0.03 mM and a sensitivity of 13 mA M(-1) cm(-2). We show that small size and homogeneous distribution of the Pd nanoparticles in combination with good conductivity and large surface area of the HCNFs lead to a H2O2 and glucose sensing platform that performs in the top range of the herein reported sensor platforms.

Glucose biosensors based on a gold nanodendrite modified screen-printed electrode

In this study, an enzymatic glucose biosensor based on a three-dimensional gold nanodendrite (GND) modified screen-printed electrode was developed. The GNDs were electrochemically synthesized on the working electrode component of a commercially available screen-printed electrode using a solution acquired by dissolving bulk gold in aqua regia as the precursor. The 3D GND electrode greatly enhanced the effective sensing area of the biosensor, which improved the sensitivity of glucose detection. Actual glucose detections demonstrated that the fabricated devices could perform at a sensitivity of 46.76 μA mM⁻¹ cm⁻² with a linear detection range from 28 μM-8.4 mM and detection limit of 7 μM. A fast response time (∼3 s) was also observed. Moreover, only a 20 μl glucose oxidase is required for detection owing to the incorporation of the commercially available screen-printed electrode.

One-pot formation of multifunctional Pt-conducting polymer intercalated nanostructures

A novel multifunctional Pt nanoparticle@PPy nanofiber intercalated structure (Pt NP@PPy NF) has been synthesized facilely in one-pot. Pt NPs, with size and facet control, were nicely assembled and embedded into the polymer nanofiber network. Polyvinylpyrrolidone (PVP) was used during the synthesis process which would assist the self-assembly of the metal nanoparticles and polymer backbones into the intercalated structure. Space-confined distribution of the Pt NPs was achieved within the large dimension PPy nanofiber network, which could enhance the interfacial electron transfer process as well as diminish the catalyst deformation. The as-formed Pt NPs have a cluster-like structure and are mainly composed of 3.5 nm primary Pt particles with (100) surface atoms. Enhanced electrocatalytic properties were shown by the Pt NP@PPy NF intercalated structure, with sufficiently high enzyme-less glucose biosensitivity and a long linear range from 1-30 mM (R = 0.9995). High electrochemical cycling stability, chloride (Cl(-)) tolerance and good selectivity are also obtained for the Pt NP@PPy NF structure, as the electrode showed no obvious response to the common interfering agents, such as ascorbic acid (AA), uric acid (UA), and 4-acetamidophenol (AP). Furthermore, the Pt NP@PPy NF showed excellent catalytic activity for the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR), which displayed sufficient CO tolerance, and higher activity compared to the commercial Pt/C catalyst. This intrinsically multifunctional Pt NP@PPy NF with well-controlled Pt facets thus could serve as an advanced electrocatalyst for biosensing and fuel cell applications, surpassing the performance of many existing materials.

Graphene oxide-induced conformation changes of glucose oxidase studied by infrared spectroscopy

The adsorption of proteins on the surface of nanomaterials can induce changes in the structure and biological activity of the proteins. Although there have been a number of studies aimed at developing an understanding of the interactions of proteins with surfaces of nanomaterials, a detailed description of the actual state of the adsorbed proteins or the functional consequences of protein adsorption onto nanomaterials has yet to be reported. In this study, the conformation changes of glucose oxidase (GOx) induced by adsorption on graphene oxide (GO) sheets were investigated by quantitative second-derivative infrared analysis and two-dimensional infrared correlation spectroscopy (2D IR). The adsorption of GOx on GO sheets resulted in the conversion of α-helix to β-sheet structures and therefore led to substantial conformation changes of GOx, even the unfolding of the protein. These alterations in the conformation of GOx caused a significant decrease in the catalytic activity of the enzyme for glucose oxidation. This study demonstrates that nanomaterials can strongly influence the conformation and activity of adsorbed proteins. In addition to the importance of this effect in cases of the direct adsorption of proteins on nanomaterials, the results have implications for proteins adsorbed on materials with nanometer-scale surface roughness.

Non-enzymatic Glucose Sensor Based on Palladium Coated Nanoporous Gold Film Electrode

The non-enzymatic voltammetric and amperometric detection of glucose using a palladium coated nanoporous gold film electrode is described. The effect of surfactant on the fabrication of nanoporous gold film was also investigated. The voltammetric detection of glucose was performed by cyclic voltammetry. The sensor had good electrocatalytic activity towards oxidation of glucose, exhibited a rapid response (~6 s), and gave a linear range from 1 to 33 mM with a detection limit of 5 μM (with a signal to noise ratio of 3). The wide dynamic range, long-term stability, high sensitivity and selectivity, good reproducibility, and high resistance towards electrode fouling resulted in an ideal inexpensive amperometric glucose biosensor applicable for complex matrices.

An aptamer-based biosensing platform for highly sensitive detection of platelet-derived growth factor via enzyme-mediated direct electrochemistry

In this work, a new label-free electrochemical aptamer-based sensor (aptasensor) was constructed for detection of platelet-derived growth factor (PDGF) based on the direct electrochemistry of glucose oxidase (GOD). For this proposed aptasensor, poly(diallyldimethylammonium chloride) (PDDA)-protected graphene-gold nanoparticles (P-Gra-GNPs) composite was firstly coated on electrode surface to form the interface with biocompatibility and huge surface area for the adsorption of GOD layer. Subsequently, gold nanoclusters (GNCs) were deposited on the surface of GOD to capture PDGF binding aptamer (PBA). Finally, GOD as a blocking reagent was employed to block the remaining active sites of the GNCs and avoid the nonspecific adsorption. With the direct electron transfer of double layer GOD membranes, the aptasensor showed excellent electrochemical response and the peak current decreased linearly with increasing logarithm of PDGF concentration from 0.005 nM to 60 nM with a relatively low limit of detection of 1.7 pM. The proposed aptasensor exhibited high specificity, good reproducibility and long-term stability, which provided a new promising technique for aptamer-based protein detection.

Sensitive detection of glucose in human serum with oligonucleotide modified gold nanoparticles by using dynamic light scattering technique

Dynamic light scattering based sensor for glucose was developed with oligonucleotide functionalized gold nanoparticles (Oligo-AuNPs). Oligonucleotide 5'-SH-(A)(12)-AGACAAGAGAGG-3' (Oligo 1) modified AuNPs and oligonucleotide 5'-CAACAGAGAACG-(A)(12)-HS-3' (Oligo 2) modified AuNPs could hybridize with oligonulceotide 5'-CGTTCTCTGTTGCCTCTCTTGTCT-3' (Oligo 3), which resulted in the aggregation of Oligo-AuNPs probes, and triggered the increase of their average diameter. However, Oligo 3 could be cleaved into DNA fragments by the mixture of glucose, glucose oxidase (GOD) and Fe(2+), and the DNA fragments could not hybridize with Oligo-AuNPs probes. Under the conditions of 3.7 nM Oligo 1-AuNPs, 3.7 nM Oligo 2-AuNPs, 8.0 μg/mL GOD, 100 nM Oligo 3 and 900 nM Fe(2+), the average diameter of Oligo-AuNPs probes decreased linearly with the increasing concentration of glucose over the range from 50 pmol/L to 5.0 nmol/L, with a detection limit of 38 pmol/L (3σ/slope). Moreover, five sugars had no effect on the average diameter of mixture of Oligo-AuNPs probes, GOD and Fe(2+), which demonstrated the good selectivity of the assay.