A novel electrochemiluminescence glucose biosensor based on alcohol-free mesoporous molecular sieve silica modified electrode

In this study, a thin-film glucose electrochemiluminescence (ECL) biosensor was developed. Ru(bpy)₃²⁺ was doped in alcohol-free low-volume shrinkage mesoporous silica sol-gel with PEG-400 as the template, and glucose dehydrogenase (GDH) was immobilized in polymer Resydrol. NADH, which is produced by the reaction of co-enzyme NAD⁺ and glucose catalyzed by glucose dehydrogenase, reacts with immobilized Ru(bpy)₃²⁺ to generate ECL emission. Among the three types of design including two-layer, mixed and sandwich configuration, the sandwich configuration showed the best sensitivity with the calibration range of 25-2000 μM and the limit of detection of 0.5 μM in a flow injection analysis of glucose. The alcohol-free mesoporous sol-gel and the sandwich design made the biosensor potentially applicable in flow-injection analysis of samples.     

Amperometric glucose biosensor based on integration of glucose oxidase with platinum nanoparticles/ordered mesoporous carbon nanocomposite

This article reports a new amperometric glucose biosensor based on ordered mesoporous carbon (OMC) supported platinum nanoparticles (Pt/OMC) modified electrode. The Pt/OMC nanocomposite modified electrode exhibited excellent electrocatalytic activities towards the reduction and oxidation of H₂O₂ as well. This feature allowed us to use it as bioplatform on which glucose oxidase (GOD) was immobilized by entrapment in electropolymerized pyrrole film for the construction of the glucose biosensor. The biosensor showed good analytical performances in terms of low detection (0.05 mM), high sensitivity (0.38 μA/mM) and wide linear range (0.05-3.70 mM). In addition, the effects of pH value, applied potential, electroactive interference and the stability of the biosensor were discussed. The applicability to blood analysis was also evaluated.     

Gold nanoparticles-coated eggshell membrane with immobilized glucose oxidase for fabrication of glucose biosensor

This work reports the fabrication and application of a glucose biosensor based on the catalytic effect of gold nanoparticles (AuNPs) on enzymatic reaction for blood glucose determination. AuNPs were initially in situ synthesized on the surface of an eggshell membrane (ESM) which was subsequently immobilized with glucose oxidase (GO_x) to produce a GO_x-AuNPs/ESM. The GO_x-AuNPs/ESM was positioned on the surface of an oxygen electrode to form a GO_x-AuNPs/ESM glucose biosensor. The effects of pH, concentration of phosphate buffer solution and amount of GO_x on the response of the GO_x-AuNPs/ESM glucose biosensor were studied in detail. AuNPs on GO_x/ESM can improve the calibration sensitivity (30% higher than GO_x/ESM without AuNPs), stability (87.3% of its initial response to glucose after 10-week storage) and shortens the response time (<30 s) of the glucose biosensor. The linear working range for the GO_x-AuNPs/ESM glucose biosensor is 8.33 μM to 0.966 mM glucose with a detection limit of 3.50 μM (S/N = 3). The biosensor has been successfully applied to determine the glucose in human blood serum samples and the results compared well to a standard spectrophotometric method commonly used in hospitals. Our work demonstrates that the developed GO_x-AuNPs/ESM glucose biosensor has potential in biomedical analysis.     

An amperometric glucose biosensor based on layer-by-layer GOx-SWCNT conjugate/redox polymer multilayer on a screen-printed carbon electrode

An amperometric glucose biosensor based on a multilayer made by layer-by-layer assembly of single-walled carbon nanotubes modified with glucose oxidase (GOx-SWCNT conjugates) and redox polymer (PVI-Os) on a screen-printed carbon electrode (SPCE) surface was developed. The SPCE surface was functionalized with a cationic polymer by electrodeposition of the PVI-Os, followed by alternating immersions in anionic GOx-SWCNT conjugate solutions and cationic PVI-O solutions. The purpose is to build a multilayer structure which is further stabilized through the electrodeposition of PVI-Os on the multilayer film. The electrochemistry of the layer-by-layer assembly of the GOx-SWCNT conjugate/PVI-Os bilayer was followed by cyclic voltammetry. The resultant glucose biosensor provided stable and reproducible electrocatalytic responses to glucose, and the electrocatalytic current for glucose oxidation was enhanced with an increase in the number of bilayers. The glucose biosensor displayed a wide linear range from 0.5 to 8.0 mM, a high sensitivity of 32 μA mM⁻¹ cm⁻², and a response time of less than 5 s. The glucose biosensor proved to be promising amperometric detectors for the flow injection analysis of glucose.     

A stable sandwich-type amperometric biosensor based on poly(3,4-ethylenedioxythiophene)-single walled carbon nanotubes/ascorbate oxidase/nafion films for detection of L-ascorbic acid

In this paper, a stable sandwich-type amperometric biosensor based on poly(3,4-ethylenedioxythiophene) (PEDOT)-single walled carbon nanotubes (SWCNT)/ascorbate oxidase (AO)/Nafion films for detection of l-ascorbic acid (AA) was successfully developed. PEDOT-SWCNT nanocomposite and Nafion films were used as inner and outer films, respectively. AO was immobilized between these two films. The PEDOT-SWCNT nanocomposite films were characterized by electrochemical impedance spectroscopy and scanning electron microscopy. The influence of detection potential and temperature on the biosensor performance was examined in detail. Despite the multilayer configuration, the biosensor exhibited a relatively fast response (less than 10 s) and a linear range from 1 μM to 18 mM (a correlation coefficient of 0.9974). The sensitivity of the biosensor was found to be 28.5 mA M⁻¹ cm⁻². Its experimental detection limit was 0.7 μM (S/N = 3) and the apparent Michaelis-Menten constant (K_m) was calculated to be 18.35 mM. Moreover, the biosensor exhibited good anti-interferent ability and excellent long-term stability. All the results showed that such sandwich-type PEDOT-SWCNT/AO/Nafion films could provide a promising platform for the biosensor designs for AA detection.     

Fabrication of novel chitosan nanofiber/gold nanoparticles composite towards improved performance for a cholesterol sensor

A novel amperometric cholesterol biosensor was fabricated by the immobilization of ChOx (cholesterol oxidase) onto the chitosan nanofibers/gold nanoparticles (designated as CSNFs/AuNPs) composite network (NW). The fabrication involves preparation of chitosan nanofibers (CSNFs) and subsequent electrochemical loading of gold nanoparticles (AuNPs). Field emission scanning electron microscopy (FE-SEM) was used to investigate the morphology of CSNFs (sizes in the range of ∼50-100 nm) and spherical AuNPs. Cyclic voltammetry, hydrodynamic voltammetry and amperometry were used to examine the performance of CSNF-AuNPs/ChOx biosensor. The CSNF-AuNPs/ChOx biosensor exhibited a wide linear response to cholesterol (concentration range of 1-45 μM), good sensitivity (1.02 μA/μM), low response time (∼5 s) and excellent long term stability. The combined existence of AuNPs within CSNFs NW provides the excellent performance of the biosensor towards the electrochemical detection of cholesterol.     

Electrochemical behaviors and determination of isoniazid at ordered mesoporous carbon modified electrode

In this work, an electrochemical sensor based on ordered mesoporous carbon (OMC) for the amperometric detection of isoniazid was developed. OMC was dispersed in a solution of Nafion, and the suspension was modified onto the surface of glassy carbon (GC) electrode. Cyclic voltammetry and amperometry were used to investigate the electrochemical behaviors of isoniazid on Nafion-OMC modified electrode (Nafion-OMC/GC). The results indicate that OMC can facilitate the electrochemical oxidation of isoniazid with a great decrease of overpotential in pH 7.0 phosphate buffer solution. The proposed biosensor provides excellent performance towards the determination of isoniazid with a high sensitivity of 0.031 μA/μM, a low detection limit of 8.4 × 10⁻⁸ M and wide linear range from 1.0 × 10⁻⁷ M to 3.7 × 10⁻⁴ M at +0.20 V vs. Ag/AgCl. The method was successfully applied to the determination of isoniazid tablets with satisfying results. All the results suggest that Nafion-OMC/GC electrode is a potential candidate for a stable and efficient electrochemical sensor to detect isoniazid.     

Noble metal dispersed multiwalled carbon nanotubes immobilized ss-DNA for selective detection of dopamine

A hybrid nanocomposite consisting of Pt nanoparticles decorated functionalized multiwalled carbon nanotubes (f-MWNT) immobilized with single strand-DNA (ss-DNA) has been devised for the selective detection of dopamine (DA). AFM and TEM analyses show that wrapping of ss-DNA over Pt/f-MWNT reduces the aggregation of the nanotubes arising from van der Waals interaction. In addition to serving as a noncovalent dispersion agent, ss-DNA facilitated electron transfer towards dopamine, as analyzed by cyclic voltammetric studies (CV) and amperometry. The sequence dependency of ss-DNA for DA detection has been analyzed using AC and GT ss-DNA. The hybrid nanocomposite biosensor consisting of AC/ss-DNA exhibits linearity of detection upto ∼315 μM, with a detection limit 0.8 μM towards dopamine. The best sensing performance with linearity of ∼800 μM and detection limit ∼0.45 μM has been obtained with GT/ss-DNA immobilized Pt/f-MWNT sensor. Further, the nafion coated ss-DNA wrapped Pt/f-MWNT immobilized biosensor exhibits good stability, fast response time (<3 s) and selective detection of DA in the presence of ascorbic acid and uric acid.     

A glucose oxidase immobilization platform for glucose biosensor using ZnO hollow nanospheres

A good route (template-directed synthetic route) for the fabrication of ZnO hollow nanospheres (ZnO-HNSPs) was proposed. ZnO hollow nanosphere is a wonderful platform to immobilize glucose oxidase for glucose biosensor owing to the high specific surface area and high isoelectric point (IEP). Along with nafion and glucose oxidase (GOD), a glucose sensor was designed. Nafion/ZnO-HNSPs/GOD/GCE displays higher catalytic activity toward the glucose oxidation than Nafion/ZnO nano-Flowers/GOD/GCE. Linear response was obtained over a concentration range from 5.0 × 10⁻³ mM to 13.15 mM with a detection limit of 1.0 μM (S/N = 3), and the sensitivity was 65.82 μA/(mM cm²). Satisfyingly, the Nafion/ZnO-HNSPs/GOD/GCE could effectively avoid the interferences from the common interfering species such as uric acid (UA), ascorbic acid (AA), dopamine (DA) and fructose. The Nafion/ZnO-HNSPs/GOD modified electrode allows high sensitivity, excellently selective, stable, and fast amperometric sensing of glucose and thus is promising for the future development of glucose sensors.     

Multiwalled carbon nanotubes grafted chitosan nanobiocomposite: A prosperous functional nanomaterials for glucose biosensor application

Multiwalled carbon nanotubes (MWNTs) grafted chitosan (CS) nanowire (NW) was prepared by phase separation method. Glucose oxidase (GOx) was sequentially immobilized into MWNT-CS-NW to obtain MWNT-CS-NW/GOx biosensor. Field emission scanning electron microscopy (FESEM) images of MWNT-CS-NW/GOx reveals the existence of MWNT and CS. Cyclic voltammetry and amperometry were used to evaluate the electrochemical determination of glucose. The MWNT-CS-NW/GOx biosensor shows an excellent performance for glucose at +0.34 V with a high sensitivity (5.03 μA/mM) and lower response time (3 s) in a wide concentration range of 1-10 mM (correlation coefficient of 0.9988). In addition, MWNT-CS-NW/GOx biosensor possesses better reproducibility, storage stability and there is negligible interference from other electroactive components.     

Development of a dehydrogenase-based glucose anode using a molecular assembly composed of nile blue and functionalized SWCNTs and its applications to a glucose sensor and glucose/O2 biofuel cell

A simple and new way to immobilize glucose dehydrogenase (GDH) enzyme onto nile blue (NB) covalently assembled on the surface of functionalized single-walled carbon nanotubes (f-SWCNTs) modified glassy carbon (GC) electrode (GDH/NB/f-SWCNTs/GC electrode) was described. The GDH/NB/f-SWCNTs/GC electrode possesses promising characteristics as glucose sensor; a wide linear dynamic range of 100-1700 μM, low detection limit of 0.3 μM, fast response time (1-2 s), high sensitivity (14 μA cm⁻² mM⁻¹), anti-interference ability and anti-fouling. Moreover, the performance of the GDH/NB/f-SWCNTs/GC bioanode was successfully tested in a glucose/O₂ biofuel cell. The maximum power density delivered by the assembled glucose/O₂ biofuel cell could reach 32.0 μW cm⁻² at a cell voltage of 0.35 V with 40 mM glucose. The present procedure can be applied for preparing a potential platform to immobilize different enzymes for various bioelectrochemical applications.     

Selective potentiometric determination of uric acid with uricase immobilized on ZnO nanowires

In this study, a potentiometric uric acid biosensor was fabricated by immobilization of uricase onto zinc oxide (ZnO) nanowires. Zinc oxide nanowires with 80-150 nm in diameter and 900 nm to 1.5 μm in lengths were grown on the surface of a gold coated flexible plastic substrate. Uricase was electrostatically immobilized on the surface of well aligned ZnO nanowires resulting in a sensitive, selective, stable and reproducible uric acid biosensor. The potentiometric response of the ZnO sensor vs Ag/AgCl reference electrode was found to be linear over a relatively wide logarithmic concentration range (1-650 μM) suitable for human blood serum. By applying a Nafion^® membrane on the sensor the linear range could be extended to 1-1000 μM at the expense of an increased response time from 6.25 s to less than 9 s. On the other hand the membrane increased the sensor durability considerably. The sensor response was unaffected by normal concentrations of common interferents such as ascorbic acid, glucose, and urea.     

Amperometric glucose microbiosensor based on a Prussian Blue modified carbon fiber electrode for physiological applications

Results of experiments in vitro and in vivo, using an amperometric glucose microbiosensor based on a Prussian Blue (PB) modified carbon fiber electrode with very low dimensions (∼10 μm diameter), are presented. The electrocatalytic properties of the PB film enable detection of an enzymatic by-product (H₂O₂) at a very low applied potential: 0.0 V against SCE. The main steps during glucose microbiosensor construction were examined by cyclic voltammetry and electrochemical impedance spectroscopy. Excellent selectivity of the glucose microbiosensors against a large number of physiological interference compounds is demonstrated. Finally, microbiosensor responses during intraperitoneal injection, local infusion and local electrical stimulation showed sufficient sensitivity and stability to monitor multi-phasic and reversible changes in brain ECF glucose levels during physiological experiments, illustrating the excellent properties and utility of this biosensor design in the neurosciences.     

One-pot electrodeposition of 3-aminopropyltriethoxysilane-chitosan hybrid gel film to immobilize glucose oxidase for biosensing

We report on the electrodeposition of a 3-aminopropyltriethoxysilane-chitosan (APTES-CS) hybrid gel film for in situ immobilization of glucose oxidase (GOx) on an Au or platinized Au (Pt_nano/Au) electrode for biosensing of glucose. Controllable electroreduction of p-benzoquinone is used to lift the electrode-surface pH for the GOx-APTES-CS codeposition, which was monitored by an electrochemical quartz crystal microbalance. The fabrication procedures of the biosensor and the parameters influencing the biosensing performance were optimized. The prepared porous GOx-APTES-CS/Pt_nano/Au and GOx-APTES-CS/Au electrodes can be used to detect the enzymatically generated H₂O₂ at 0.5 and 0.7 V vs SCE, respectively. The enzyme electrodes exhibited linear responses to glucose concentration from 0.2 μM to 8.2 mM (R = 0.998, at Pt_nano/Au substrate) and from 0.2 μM to 5.5 mM (R = 0.998, at Au substrate), with current sensitivities of 69.5 (Pt_nano/Au) and 65 (Au) μA mM⁻¹ cm⁻², respectively, and a detection limit of 0.2 μM (S/N = 3) was achieved for each electrode. The response time was less than 5 (Pt_nano/Au) or 8 (Au) s. It is striking that the enzyme electrodes remained their initial response sensitivity after storage for 5 (Au) and >6 (Pt_nano/Au) months in 0.10 M PBS (pH 7.0) at 4 °C.     

Study of an amperometric glucose sensor based on Pd-Ni/SiNW electrode

An amperometric glucose sensor based on Pd-Ni/SiNW electrode has been investigated. The silicon nanowire (SiNW) electrodes were first fabricated by chemical etching, and then nickel and palladium particles were deposited onto the surfaces of SiNWs via electroless co-plating technique followed by annealing in nitrogen atmosphere at 350 °C for 300 s. The morphology of Pd-Ni/SiNW electrode was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The sensor performance was characterized by cyclic voltammetry (CV) and fixed potential amperometry techniques. In 0.1 M KOH alkaline medium with different glucose concentrations, the sensor shows an excellent sensitivity of 190.72 μA mM⁻¹ cm⁻² with the detection limit (S/N ratio = 3) of 2.88 μM. And it also exhibits superior anti-interference properties to the species including ascorbic acid (AA), uric acid (UA) and 4-acetamidophenol (AP). All results demonstrate that this Pd-Ni/SiNW electrode is a candidate with great potential for glucose detection.     

Amperometric biosensor for catechol using electrochemical template process

A novel amperometric biosensor for the determination of catechol was developed accordingly to the electrochemical template procedure. The optimum fabricating conditions of the biosensor were studied. The resulting biosensor with the limit of less than 0.05 μM can be used for detection of catechol in the linear range of 2.5-140 μM. The maximum response current (I_max) and the Michaelis-Menten constant (k′_m) are 3.08 μA and 77.52 μM, respectively. The activation energy (E_a) of the polyphenol oxidase (PPO) catalytic reaction is 25.56 kJ mol⁻¹ in the B-R buffer. The stability of the PANI-CA biosensor fabricated with the electrochemical template process (retains 86% of the original activity after four months) is much higher than that fabricated with one-step and two-step processes (retains 75% of the original activity after four months). The effects of potential and pH on the response current of the biosensor are also described.     

Hybridization biosensor based on the covalent immobilization of probe DNA on chitosan-mutiwalled carbon nanotubes nanocomposite by using glutaraldehyde as an arm linker

A label-free DNA biosensor for hybridization detection of short DNA species related to the transgenic plants gene fragment of cauliflower mosaic virus (CaMV) 35S promoter was developed in this paper. The nanocomposite containing chitosan (CS) and mutiwalled carbon nanotubes (MWNTs) was first coated on a glassy carbon electrode. Then a highly reactive dialdehyde reagent of glutaraldehyde (GTD) was applied as an arm linker to covalently graft the 5′-amino modified probe DNA to the CS-MWNTs surface via the facile aldehyde-ammonia condensation reaction. The hybridization capacity of the developed biosensor was monitored with electrochemical impedance spectroscopy (EIS) using [Fe(CN)₆]^3−/4− as an indicating probe, and the experimental results showed that the biosensor had fast hybridization rate and low background interference. A wide dynamic detection range (1.0 × 10⁻¹³-5 × 10⁻¹⁰ M) and a low detection limit (8.5 × 10⁻¹⁴ M) were achieved for the complementary sequence. In addition, the hybridization specificity experiments showed that the sensing system can accurately discriminate complementary sequence from mismatch and noncomplementary sequences.     

An electrochemical biosensor for determination of hydrogen peroxide using nanocomposite of poly(methylene blue) and FAD hybrid film

An electrochemical biosensor for determination of hydrogen peroxide (H₂O₂) has been developed by the hybrid film of poly(methylene blue) and FAD (PMB/FAD). The PMB/FAD hybrid film was performed in PBS (pH 7) containing methylene blue and FAD by cyclic voltammetry. Repeatedly scanning potential range of −0.6-1.1 V, FAD was immobilized on the electrode surface by electrostatic interaction while methylene blue was electropolymerized on electrode surface. This modified electrode was found surface confined and pH dependence. It showed good electrocatalytic reduction for H₂O₂, KBrO₃, KIO₃, and NaClO as well as electrocatalytic oxidation for NADH. At an applied potential of −0.45 V vs. Ag/AgCl, the sensor showed a rapid and linear response to H₂O₂ over the range from 0.1 μM to 960 μM, with a detection limit of 0.1 μM and a significant sensitivity of 1109 μA mM⁻¹ cm⁻² (S/N = 3). It presented excellent stability at room temperature, with a variation of response current less than 5% over 30 days.     

Analysis of volatile alcohols in apple juices by an electrochemical biosensor measuring in the headspace above the liquid

An electrochemical biosensor was optimised for the analysis of volatile alcohols directly from the gas phase without prior absorption or pre-concentration. The sensor is based on the alcohol oxidase (Pichia pastoris) catalyzed conversion of ethanol and the amperometric detection of the generated hydrogen peroxide. Key part of the three-electrode set-up was a gas-diffusion working electrode (potential: +600 mV vs. Ag/AgCl) that consisted of a porous Teflon membrane coated with a thin platinum layer. Headspace samples were analysed for alcohols and used to derive alcohol concentrations in the liquid phase. The biosensor had a sensitivity of 3.43 μA/mM for ethanol, a response time of 69 s, a linear dynamic range of 0.10-30 mM, a theoretical detection limit (3 < S/N) of 9.9 μM, and a stability of 86% during continuous operation (18 h @ 1 mM ethanol). Using one sensor on three consecutive days, the mean coefficient of variation was 1.3% (three measurements each day @ 10 mM ethanol). Alcohol contents of three apple juices determined with the biosensor were in the range 0.30 g/l-0.67 g/l (equivalent to 6.51 mM-14.5 mM). However, ethanol contents determined by high pressure liquid chromatography coupled to refractive index detection (HPLC-RI) and by a commercial enzyme test kit based on alcohol dehydrogenase ranged from 0.12 g/l to 0.38 g/l (equivalent to 2.60 mM-8.25 mM). Both indicate that the biosensor detected alcohols other than ethanol in the apple juices. HPLC-RI coupled to the biosensor in a flow-through configuration demonstrated that the biosensor detected methanol concomitant to ethanol. Thus, the biosensor could perform a qualitative analysis of the total content of volatile alcohols in apple juices by analysing the gas phase above the sample. This offers the additional advantage that possible, non-volatile interfering substances in the liquid sample cannot impair the measurement.     

An amperometric biosensor based on lactate oxidase immobilized in laponite-chitosan hydrogel on a glassy carbon electrode. Application to the analysis of l-lactate in food samples

A biosensor based on the immobilization of lactate oxidase (LOx) on a glassy carbon electrode modified with laponite/chitosan hydrogels for the quantification of l-lactate in alcoholic beverages and dairy products is presented. Ferrocene-methanol (FcMe) is used as artificial mediator. The purpose of this work is to determine the best hydrogel composition from the analytical point of view. The characterization of the hydrogels was carried out by CV, amperometry and EIS. According to permeabilities and charge transfer resistances for ferrocyanide (used as molecular probe) as well as the enzymatic behavior of the enzyme for l-lactate, the best laponite/chitosan mass ratio found was 25/50. The distinct features of the bioelectrode are its long stability, its ability to reject or minimize most interferents including ascorbic acid, and its excellent analytical response, which allowed the reduction of the enzyme content below 0.5 U, for a sensitivity of (0.326 ± 0.003) A cm⁻² M⁻¹, with a time response lower than 5 s and a detection limit of (3.8 ± 0.2) × 10⁻⁶ M. Our l-lactate biosensor was validated by comparison with a standard spectroscopic method.