Glucose biosensor based on titanium dioxide-multiwall carbon nanotubes-chitosan composite and functionalized gold nanoparticles

In this paper, a new glucose biosensor was prepared. At first, Prussian blue (PB) was electrodeposited on a glassy carbon electrode (GCE) modified by titanium dioxide-multiwall carbon nanotubes-chitosan (TiO₂-MWNTs-CS) composite, and then gold nanoparticles functionalized by poly(diallyldimethylammonium chloride) (PDDA-Au) were adsorbed on the PB film. Finally, the negatively charged glucose oxidase (GOD) was self-assembled on to the positively charged PDDA-Au. The electrochemical performances of the modified electrodes had been studied by cyclic voltammetry (CV) and amperometric methods, respectively. In addition, the stepwise fabrication process of the as-prepared biosensor was characterized by scanning electron microscopy. PDDA-Au nanoparticles were characterized by ultraviolet–vis absorption spectroscopy and transmission electron microscopy. Under the optimal conditions, the as-prepared biosensor exhibited a good response performance to glucose with a linear range from 6 μM to 1.2 mM with a detection limit of 0.1 μM glucose (S/N = 3). In addition, this work indicated that TiO₂-MWNTs-CS composite and PDDA-Au nanoparticles held great potential for constructing biosensors.     

A high-sensitive and fast-fabricated glucose biosensor based on Prussian blue/topological insulator Bi(2)Se(3) hybrid film

A novel and fast-fabricated Prussian blue (PB)/topological insulator Bi(2)Se(3) hybrid film has been prepared by coelectrodeposition technique. Taking advantages of topological insulator in possessing exotic metallic surface states with bulk insulating gap, Prussian blue nanoparticles in the hybrid film have smaller size as well as more compact structure, showing excellent pH stability even in the alkalescent solution of pH 8.0. Based on the Laviron theory, the electron transfer rate constant of PB/Bi(2)Se(3) hybrid film modified electrode was calculated to be 4.05±0.49s(-1), a relatively big value which may be in favor of establishing a high-sensitive biosensor. An amperometric glucose biosensor was then fabricated by immobilizing glucose oxidase (GOD) on the hybrid film. Under the optimal conditions, a wide linear range extending over 3 orders of magnitude of glucose concentrations (1.0×10(-5)-1.1×10(-2)M) was obtained with a high sensitivity of 24.55μAmM(-1) cm(-2). The detection limit was estimated for 3.8μM defined from a signal/noise of 3. Furthermore, the resulting biosensor was applied to detect the blood sugar in human serum samples without any pretreatment, and the results were comparatively in agreement with the clinical assay.     

Amperometric sensor based on ferrocene-modified multiwalled carbon nanotube nanocomposites as electron mediator for the determination of glucose

A kind of nanocomposite with good dispersion in water was prepared through covalent adsorption of ferrocenecarboxaldehyde on multiwalled carbon nanotubes (MWNTs) for electrical communication between glucose oxidase (GOD) and electrode. The ferrocene-modified multiwalled carbon nanotube nanocomposites (MWNTs-Fc) could be conveniently cast on electrode surfaces. With the aid of chitosan, GOD was then immobilized on the nanostructure film to form a reagentless amperometric sensor for glucose determination. FTIR spectra and cyclic voltammetry were used to characterize the nanocomposites. The presence of both ferrocene as mediator of electron transfer and MWNTs as conductor enhanced greatly the enzymatic response to the oxidation of glucose. The novel biosensor exhibited a fast response toward glucose with a detection limit of 3.0 × 10⁻⁶ mol/L and the linear range extended up to 3.8 × 10⁻³ mol/L.     

A porous poly(acrylonitrile-co-acrylic acid) film-based glucose biosensor constructed by electrochemical entrapment

A novel glucose biosensor was constructed by electrochemical entrapment of glucose oxidase (GOD) into porous poly(acrylonitrile-co-acrylic acid), which was synthesized via radical polymerization of acrylonitrile and acrylic acid. The obtained biosensor showed a better stability and higher sensitivity than the biosensor prepared by simple physical adsorption. Effects of some experimental variables such as immobilization time, enzyme concentration, pH, applied potential, and temperature on the amperometric response of the sensor were investigated. The biosensor exhibited a rapid response to glucose (< 30s) with a linear range of 5 x 10(-6) to 3 x 10(-3)M and a sensitivity of 6.82 mAM(-1)cm(-2). The apparent Michaelis-Menten constant (K(M)(app)) was 7.3mM.     

A novel glucose biosensor based on the immobilization of glucose oxidase onto gold nanoparticles-modified Pb nanowires

A novel glucose biosensor was developed, based on the immobilization of glucose oxidase (GOD) with cross-linking in the matrix of bovine serum albumin (BSA) on a Pt electrode, which was modified with gold nanoparticles decorated Pb nanowires (GNPs-Pb NWs). Pb nanowires (Pb NWs) were synthesized by an l-cysteine-assisted self-assembly route, and then gold nanoparticles (GNPs) were attached onto the nanowire surface through –SH–Au specific interaction. The morphological characterization of GNPs-Pb NWs was examined by transmission electron microscopy (TEM). Cyclic voltammetry and chronoamperometry were used to study and to optimize the electrochemical performance of the resulting biosensor. The synergistic effect of Pb NWs and GNPs made the biosensor exhibit excellent electrocatalytic activity and good response performance to glucose. The effects of pH and applied potential on the amperometric response of the biosensor have been systemically studied. In pH 7.0, the biosensor showed the sensitivity of 135.5 μA mM⁻¹ cm⁻², the detection limit of 2 μM (S/N = 3), and the response time <5 s with a linear range of 5–2200 μM. Furthermore, the biosensor exhibits good reproducibility, long-term stability and relative good anti-interference.     

Direct electrochemistry and electrocatalysis of glucose oxidase immobilized on glassy carbon electrode modified by Nafion and ordered mesoporous silica-SBA-15

In this paper, it was found that glucose oxidase (GOD) has been stably immobilized on glassy carbon electrode modified by ordered mesoporous silica-SBA-15 and Nafion. The sorption behavior of GOD immobilized on SBA-15 matrix was characterized by transmission electron microscopy (TEM), ultraviolet–visible (UV–vis), FTIR, respectively, which demonstrated that SBA-15 can facilitate the electron exchange between the electroactive center of GOD and electrode. The direct electrochemistry and electrocatalysis behavior of GOD on modified electrode were characterized by cyclic voltammogram (CV) which indicated that GOD immobilized on Nafion and SBA-15 matrices displays direct, nearly reversible and surface-controlled redox reaction with an enhanced electron transfer rate constant of 3.89 s⁻¹ in 0.1 M phosphate buffer solution (PBS) (pH 7.12). Furthermore, it was also discovered that, in the absence of O₂, GOD immobilized on Nafion and SBA-15 matrices can produce a wide linear response to glucose in the positive potential range. Thus, Nafion/GOD-SBA-15/GC electrode is hopeful to be used in the third non-mediator's glucose biosensor. In addition, GOD immobilized on SBA-15 and Nafion matrices possesses an excellent bioelectrocatalytic activity for the reduction of O₂. The Nafion/GOD-SBA-15/GC electrode can be utilized as the cathode in biofuel cell.     

Amperometric glucose biosensor based on multilayer films via layer-by-layer self-assembly of multi-wall carbon nanotubes, gold nanoparticles and glucose oxidase on the Pt electrode

A novel amperometric glucose biosensor based on the nine layers of multilayer films composed of multi-wall carbon nanotubes (MWCNTs), gold nanoparticles (GNp) and glucose oxidase (GOD) was developed for the specific detection of glucose. MWCNTs were chemically modified with the H₂SO₄–HNO₃ pretreatment to introduce carboxyl groups which were used to interact with the amino groups of poly(allylamine) (PAA) and cysteamine via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide cross-linking reaction, respectively. A cleaned Pt electrode was immersed in PAA, MWCNTs, cysteamine and GNp, respectively, followed by the adsorption of GOD, assembling the one layer of multilayer films on the surface of Pt electrode (GOD/GNp/MWCNTs/Pt electrode). Repeating the above process could assemble different layers of multilayer films on the Pt electrode. PBS washing was applied at the end of each assembly deposition for dissociating the weak adsorption. Film assembling and characterization were studied by transmission electron microscopy and quartz crystal microbalance, and properties of the resulting glucose biosensors were measured by electrochemical measurements. The marked electrocatalytic activity of Pt electrode based on multilayer films toward H₂O₂ produced during GOD enzymatic reactions with glucose permitted effective low-potential amperometric measurement of glucose. Taking the sensitivity and selectivity into consideration, the applied potential of 0.35 V versus Ag/AgCl was chosen for the oxidation detection of H₂O₂ in this work. Among the resulting glucose biosensors, the biosensor based on nine layers of multilayer films was best. It showed a wide linear range of 0.1–10 mM glucose, with a remarkable sensitivity of 2.527 μA/mM, a detection limit of 6.7 μM estimated at a signal-to-noise ratio of 3 and fast response time (within 7 s). Moreover, it exhibited good reproducibility, long-term stability and the negligible interferences of ascorbic acid, uric acid and acetaminophen. The study can provide a feasible approach on developing new kinds of oxidase-based amperometric biosensors, and can be used as an illustration for constructing various hybrid structures.     

A novel glucose biosensor based on the nanoscaled cobalt phthalocyanine-glucose oxidase biocomposite

We report on the utilization of a novel nanoscaled cobalt phthalocyanine (NanoCoPc)-glucose oxidase (GOD) biocomposite colloid to create a highly responsive glucose biosensor. The biocomposite colloid is constructed under enzyme-friendly conditions by adsorbing GOD molecules on CoPc nanoparticles via electrostatic interactions. The glucose biosensor can be easily achieved by casting the biocomposite colloid on a pyrolytic graphite electrode (PGE) without any auxiliary matter. It has been found that GOD can be firmly immobilized on PGE surface and maintain its bioactivity after conjugating with NanoCoPc. NanoCoPc displays intrinsic electrocatalytic ability to the oxidation of the product of enzymatic reaction H2O2 and shows a higher catalytic activity than that of bulk CoPc. Under optimal conditions, the biosensor shows a wide linear response to glucose in the range of 0.02-18 mM, with a fast response (5s), high sensitivity (7.71 microA cm(-2) mM(-1)), as well as good thermostability and long-term life. The detection limit was 5 microM at 3 sigma. The general interferences coexisted in blood except ascorbic acid and L-cysteine do not affect glucose determination, and further coating Nafion film on the surface of the biosensor can effectively eliminate the interference from ascorbic acid and L-cysteine. The biosensor with Nafion film has been used for the determination of glucose in serum with an acceptable accuracy.     

An amperometric glucose biosensor based on poly(o-aminophenol) and Prussian blue films at platinum electrode

Prussian blue (PB), as a good catalyst for the reduction of hydrogen peroxide, has been combined with nonconducting poly(o-aminophenol) (POAP) film to assemble glucose biosensor. Compared with PB-modified enzymatic biosensor, the biosensor based on glucose oxidase immobilized in POAP film at PB-modified electrode shows much improved stability (78% remains after 30 days) in neutral medium. Additionally, the biosensor, at an applied potential of 0.0 V, exhibits other good characteristics, such as relative low detection limit (0.01 mM), short response time (within 5s), large current density (0.28 mA/cm2), high sensitivity (24 mAM(-1)cm(-2)), and good antiinterferent ability. The apparent activation energy of enzyme-catalyzed reaction and apparent Michaelis-Menten constant are 34.2 KJmol(-1) and 10.5 mM, respectively. In addition, effects of temperature, applied potential used in the determination, pH value of the detection solution, and electroactive interferents on the amperometric response of the sensor were investigated and are discussed.     

Construction of an amperometric glucose biosensor based on the immobilization of glucose oxidase onto electrodeposited Pt nanoparticles-chitosan composite film

One-step construction of Pt nanoparticles-chitosan composite film (PtNPs-CS) was firstly proposed as a novel immobilization matrix for the enzymes to fabricate glucose biosensor. This novel interface embedded in situ PtNPs in CS hydrogel was developed by one-step electrochemical deposition in solution containing CS and chloroplatinic acid (H(2)PtCl(6)). Several techniques, including scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry were employed to characterize the assembly process and performance of the biosensor. Under the optimized experimental conditions, the resulting biosensor exhibited excellent linear behavior in the concentration range from 1.2 μM to 4.0 mM for the quantitative analysis of glucose with a limit of detection of 0.4 μM at a signal-to-noise ratio of 3. The apparent Michaelis-Menten constant (K(M)(app)) was evaluated to be 2.4 mM, showing good affinity. The proposed biosensor offered good amperometric responses to glucose due to the nanostructured sensing film provided plenty of active sites for the immobilization of glucose oxidase (GOD).     

Chemiluminescence flow-through biosensor for glucose with eggshell membrane as enzyme immobilization platform

In this study, a new chemiluminescence (CL) flow-through biosensor for glucose was developed by immobilizing glucose oxidase (GOD) and horseradish peroxidase (HRP) on the eggshell membrane with glutaraldehyde as a cross-linker. The CL detection involved enzymatic oxidation of glucose to D-gluconic acid and hydrogen peroxide (H2O2) and then H2O2 oxidizing luminol to produce CL emission in the presence of HRP. The immobilization condition (e.g., immobilization time, GOD/HRP ratio, glutaraldehyde concentration) was studied in detail. It showed good storage stability at 4 degrees C over a 5-month period. The proposed biosensor exhibited short response time, high sensitivity, easy operation, and simple sensor assembly, and the proposed biosensor was successfully applied to the determination of glucose in human serum.     

Glucose biosensor based on immobilization of glucose oxidase in poly(o-aminophenol) film on polypyrrole-Pt nanocomposite modified glassy carbon electrode

Novel Pt nanoclusters embedded polypyrrole nanowires (PPy-Pt) composite was electrosynthesized on a glassy carbon electrode, denoted as PPy-Pt/GCE. A glucose biosensor was further fabricated based on immobilization of glucose oxidase (GOD) in an electropolymerized non-conducting poly(o-aminophenol) (POAP) film that was deposited on the PPy-Pt/GCE. The morphologies of the PPy nanowires and PPy-Pt nanocomposite were characterized by field emission scanning electron microscope (FE-SEM). Effect of experimental conditions involving the cycle numbers for POAP deposition and Pt nanoclusters deposition, applied potential used in glucose determination, temperature and pH value of the detection solution were investigated for optimization. The biosensor exhibited an excellent current response to glucose over a wide linear range from 1.5 × 10⁻⁶ to 1.3 × 10⁻² M (r = 0.9982) with a detection limit of 4.5 × 10⁻⁷ M (s/n = 3). Based on the combination of permselectivity of the POAP and the PPy films, the sensor had good anti-interference ability to ascorbic acid (AA), uric acid (UA) and acetaminophen. The apparent Michaelis–Menten constant (K_m) and the maximum current density (I_m) were estimated to be 23.9 mM and 378 μA/cm², respectively. In addition, the biosensor had also good sensitivity, stability and reproducibility.     

A mediator-free glucose biosensor based on glucose oxidase/chitosan/α-zirconium phosphate ternary biocomposite

A novel glucose oxidase/chitosan/α-zirconium phosphate (GOD/chitosan/α-ZrP) ternary biocomposite was prepared by co-intercalating glucose oxidase (GOD) and chitosan into the interlayers of α-zirconium phosphate (α-ZrP) via a delamination–reassembly procedure. The results of X-ray diffraction, infrared spectroscopy, circular dichroism, and ultraviolet spectrum characterizations indicated not only the layered and hybrid structure of the GOD/chitosan/α-ZrP ternary biocomposite but also the recovered activity of the intercalated GOD improved by the co-intercalated chitosan. By depositing the GOD/chitosan/α-ZrP biocomposite film onto a glassy carbon electrode, the direct electrochemistry of the intercalated GOD was achieved with a fast electron transfer rate constant, k_s, of 7.48 ± 3.52 s⁻¹. Moreover, this GOD/chitosan/α-ZrP biocomposite modified electrode exhibited a sensitive response to glucose in the linear range of 0.25–8.0 mM (R = 0.9994, n = 14), with a determination limit of 0.076 mM.     

The direct electron transfer of glucose oxidase and glucose biosensor based on carbon nanotubes/chitosan matrix

The glucose oxidase (GOD) is entrapped in the composite of carbon nanotubes/chitosan and direct electron transfer reaction between GOD and electrode takes place. The electron transfer rate of GOD is greatly enhanced to 7.73 s(-1) in the system, which is more than one-fold higher than that of flavin adenine dinucleotide adsorbed on the carbon nanotubes (3.1 s(-1)). This maybe results from the conformational change of GOD in the microenvironment enabling the accessibility of active site for GOD to the electrode. Additionally, the bioactivity of GOD modified in the composite on electrode surface is kept. So as-prepared electrode can be used as a glucose biosensor exhibiting higher sensitivity (0.5 microA mM(-1)) and better stability. The facile procedure of immobilizing GOD will promote the developments of electrochemical research for protein, biosensors and other bioelectrochemical devices.     

Glucose biosensor based on electrodeposited platinum nanoparticles and three-dimensional porous chitosan membranes

The chitosan with three-dimensional porous structure greatly increased the effective electrode surface for loading of platinum nanoparticles and promoted efficient electron transfer. The resulting biosensor had a response time (within 5 s) and a linear response from 6 μM to 4.2 mM glucose with a detection limit of 2 μM (S/N = 3). Moreover, the methodology can be applied for the immobilization of other enzymes.     

A noninterference polypyrrole glucose biosensor

In order to eliminate the interference of impurities, such as ascorbic acid, a noninterference polypyrrole glucose biosensor was constructed with a four-electrode cell consisting of a polypyrrole film electrode, a polypyrrole-glucose oxidase electrode, a counter electrode and a reference electrode. The pure catalytic current of glucose oxidase (GOD) can be obtained from the difference between response currents of two working electrodes with and without GOD. The effects of potential, pH and temperature on analytical performance of the glucose biosensor were discussed. The optimum pH and apparent activation energy of enzyme-catalyzed reaction are 5.5 and 25 kJ mol(-1), respectively. The response current of the biosensor increases linearly with the increasing glucose concentration from 0.005 to 20.0 mmol dm(-3). The results show the glucose biosensor with under 2% of relative deviation has good ability of anti-interference. The glucose biosensor was also characterized with FT-IR and UV-vis spectra.     

Development of a disposable glucose biosensor using electroless-plated Au/Ni/copper low electrical resistance electrodes

This paper presents a glucose biosensor, which was developed using a Au/Ni/copper electrode. Until now, research regarding the low electrical resistance and uniformity of this biosensor electrode has not been conducted. Glucose oxidase (GOD) immobilized on the electrode effectively plays the role of an electron shuttle, and allows glucose to be detected at 0.055 V with a dramatically reduced resistance to easily oxidizable constituents. The Au/Ni/copper electrode has a low electrical resistance, which is less than 0.01 Ω, and it may be possible to mass produce the biosensor electrode with a uniform electrical resistance. The low electrical resistance has the advantage in that the redox peak occurs at a low applied potential. Using a low operating potential (0.055 V), the GOD/Au/Ni/copper structure creates a good sensitivity to detect glucose, and efficiently excludes interferences from common coexisting substances. The GOD/Au/Ni/copper sensor exhibits a relatively short response time (about 3 s), and a sensitivity of 0.85 μA mM⁻¹ with a linear range of buffer to 33 mM of glucose. The sensor has excellent reproducibility with a correlation coefficient of 0.9989 (n = 100 times) and a total non-linearity error of 3.17%.     

Fabrication of ultra-thin polypyrrole-glucose oxidase film from supporting electrolyte-free monomer solution for potentiometric biosensing of glucose

A simple electropolymerisation process is described for the fabrication of an ultra-thin ( approximately 55 nm) polypyrrole (PPy)-glucose oxidase (GOD) film in a supporting electrolyte-free monomer solution for potentiometric biosensing of glucose. The optimum conditions for growing the ultra-thin film include 0.1 M pyrrole, 55-110 U/ml GOD, an applied current density of 0.05 mA/cm(2) and an electrical charge of 25 mC/cm(2). Long-term storage of the biosensor in acetate buffer improved the sensitivity of the biosensor by a factor of approximately two. The biosensor can also be used repeatedly for over 2 months with little or no loss in sensitivity. The interference effect of ascorbic acid was successfully reduced by inclusion of an outer PPy-Cl layer.     

Amperometric glucose biosensor based on single-walled carbon nanohorns

The biosensing application of single-walled carbon nanohorns (SWCNHs) was demonstrated through fabrication of an amperometric glucose biosensor. The biosensor was constructed by encapsulating glucose oxidase in the Nafion-SWCNHs composite film. The cyclic voltammograms for glucose oxidase immobilized on the composite film displayed a pair of well-defined and nearly symmetric redox peaks with a formal potential of -0.453 V. The biosensor had good electrocatalytic activity toward oxidation of glucose. To decrease detection potential, ferrocene monocarboxylic acid was used as a redox mediator. The mediated glucose biosensor shows a linear range from 0 to 6.0 mM. The biosensor shows high sensitivity (1.06 microA/mM) and stability, and can avoid the commonly coexisted interference. Because of impressive properties of SWCNHs, such as high purity and high surface area, SWCNHs and their composites are expected to be promising material for biomolecular immobilization and biosensing applications.     

Glucose biosensor based on immobilization of glucose oxidase in poly(o-aminophenol) film on polypyrrole-Pt nanocomposite modified glassy carbon electrode

Novel Pt nanoclusters embedded polypyrrole nanowires (PPy-Pt) composite was electrosynthesized on a glassy carbon electrode, denoted as PPy-Pt/GCE. A glucose biosensor was further fabricated based on immobilization of glucose oxidase (GOD) in an electropolymerized non-conducting poly(o-aminophenol) (POAP) film that was deposited on the PPy-Pt/GCE. The morphologies of the PPy nanowires and PPy-Pt nanocomposite were characterized by field emission scanning electron microscope (FE-SEM). Effect of experimental conditions involving the cycle numbers for POAP deposition and Pt nanoclusters deposition, applied potential used in glucose determination, temperature and pH value of the detection solution were investigated for optimization. The biosensor exhibited an excellent current response to glucose over a wide linear range from 1.5 × 10⁻⁶ to 1.3 × 10⁻² M (r = 0.9982) with a detection limit of 4.5 × 10⁻⁷ M (s/n = 3). Based on the combination of permselectivity of the POAP and the PPy films, the sensor had good anti-interference ability to ascorbic acid (AA), uric acid (UA) and acetaminophen. The apparent Michaelis–Menten constant (K_m) and the maximum current density (I_m) were estimated to be 23.9 mM and 378 μA/cm², respectively. In addition, the biosensor had also good sensitivity, stability and reproducibility.