An enzyme free potentiometric detection of glucose based on a conducting polymer poly (3-aminophenyl boronic acid-co-3-octylthiophene)

Chemosensitive Properties of Electrochemically Synthesized Poly-3-Thienylboronic Acid: Conductometric Detection of Glucose and Other Diol-Containing Compounds under Electrical Affinity Control

Due to the presence of the boronic acid moieties, poly-3-thienylboronic acid has an affinity for saccharides and other diol-containing compounds. Thin films of this novel chemosensitive polymer were synthesized electrochemically on the gold surface. The adhesion of the polymer was enhanced by the deposition of a monomolecular layer of thiophenol. The technology was used to fabricate conductometric sensors for glucose and other diol-containing compounds. Simultaneous two- and four-electrode conductivity measurements were performed. The chemical sensitivity to sorbitol, fructose, glucose, and ethylene glycol was studied at different pH and electrode potentials, and the corresponding binding constants were obtained. Depending on the electrode potential, the reciprocal values of the binding constants of glucose to poly-3-thienylboronic acid at neutral pH are in the range of 0.2 mM-1.0 mM. The affinity for glucose has been studied in buffer solutions and in solutions containing the major components of human blood. It was shown that the presence of human serum albumin increases the affinity of poly-3-thienylboronic acid for diol-containing compounds.

Construction of a novel nano-enzyme for ultrasensitive glucose detection with surface-enhanced Raman scattering

Fabricating more sensitive, stable and low-cost nanomaterials for the detection of glucose is important for the disease diagnosis and monitoring. Herein, we established a nanocomposite (polypyrrole bridging GO@Au@MnO₂) as a novel surface-enhanced Raman scattering (SERS) nanoprobe for the quantitative detection of glucose in trace serum. Each component in the nanocomposites played an irreplaceable role in SERS detection of glucose. Polypyrrole (PPy) could act as Raman signal and extra SERS signal molecules didn't need to be introduced; Graphene oxide (GO) and gold nanoparticles (Au NPs) could enhance Raman signal of PPy; Au NPs also acted as glucose oxidase, which can oxidize glucose to produce gluconic acid and hydrogen peroxide(H₂O₂); Manganese oxide (MnO₂) further enhanced Raman signal of PPy and responded to hydrogen peroxide, which will induce the decrease of Raman intensity of PPy. Thus, glucose can be quantified according to Raman signal output of PPy, which displayed a liner range from 1 to 10 μM, with detectable limit of 0.114 μM. Because of the merits in sensitivity, convenience and versatility, the novel method shows large potential space for disease-related substance detection in the future.

3D Nanocomposite with High Aspect Ratio Based on Polyaniline Decorated with Silver NPs: Synthesis and Application as Electrochemical Glucose Sensor

In this paper, we present a new methodology for creating 3D ordered porous nanocomposites based on anodic aluminum oxide template with polyaniline (PANI) and silver NPs. The approach includes in situ synthesis of polyaniline on templates of anodic aluminum oxide nanomembranes and laser-induced deposition (LID) of Ag NPs directly on the pore walls. The proposed method allows for the formation of structures with a high aspect ratio of the pores, topological ordering and uniformity of properties throughout the sample, and a high specific surface area. For the developed structures, we demonstrated their effectiveness as non-enzymatic electrochemical sensors on glucose in a concentration range crucial for medical applications. The obtained systems possess high potential for miniaturization and were applied to glucose detection in real objects-laboratory rat blood plasma.

Imprinted-Zeolite-X-Based Sensor for Non-Enzymatic Detection of Blood Glucose by Potentiometry

The development of sensors based on imprinted zeolite X to detect blood glucose through potentiometry was performed. In this study, the sensor was made of a mixture of carbon paste and imprinted zeolite X. Zeolite X was synthesized using a sol–gel-hydrothermal method at a temperature of 100 °C with basic materials of NaAlO2, NaOH, TEOS, and distilled water. The characterization results of XRD showed the presence of specific peaks, which were confirmed with standard zeolite X. Imprinted zeolite X exhibited a 20 times greater adsorption capacity size, and an adsorption efficiency 3 times greater than that of zeolite X. This is thought to be due to the presence of a molecular template within it. The IZ–carbon paste electrode showed optimum performance due to a mass ratio of carbon, paraffin, and imprinted zeolite X of 12:7:1. The electrode performance was expressed by the Nernst factor value of 30 mV/decade, the measuring range of 10−4–10−2 M, the upper detection limit of 1.38 × 10−2 M, and the lower detection limit of 1.28 × 10−4 M, so this electrode can be used for glucose analysis with a normal concentration (70–110 mg/dL or equivalent to 3.8 × 10−3–6.1 × 10−3 M), as well as the glucose concentration of people with diabetes mellitus (>200 mg/dL or about 10−2 M). This electrode showed precision values of 97.14–99.02%, accuracy values of 98.65–99.39%, and electrode response times of 10–13 s. The electrodes showed high stability for more than 5 weeks with 141 uses. The electrodes also showed high selectivity for glucose in the matrix of uric acid, urea, NaCl, and KCl. Therefore, its use as an alternative electrode for routine glucose analysis in the medical field is recommended.

3-Thienylboronic Acid as a Receptor for Diol-Containing Compounds: A Study by Isothermal Titration Calorimetry

The electrochemical activity of 3-thienylboronic acid and its feature to form polymer films makes it a perspective receptor material for sensor applications. The affinity properties of this compound were studied here by isothermal titration calorimetry. A number of different analytes were tested, and the highest binding enthalpy was observed for sorbitol and fructose. An increase of pH in the range of 5.5–10.6 results in the rise of the binding enthalpy with an increase of the binding constant to ~8400 L/mol for sorbitol or ~3400 L/mol for fructose. The dependence of the binding constant on pH has an inflection point at pH 7.6 with a slope that is a ten-fold binding constant per one pH unit. The binding properties of 3-thienylboronic acid were evaluated to be very close to that of the phenylboronic acid, but the electrochemical activity of 3-thienylboronic acid provides a possibility of external electrical control: dependence of the affinity of 3-thienylboronic acid on its redox state defined by the presence of ferro/ferricyanide in different ratios was demonstrated. The results show that 3-thienylboronic acid can be applied in smart chemical sensors with electrochemically controllable receptor affinity.

Boronate-appended polymers with diol-functionalized ferrocene: an effective and selective method for voltammetric glucose sensing

In this research, three types of poly(amidoamine) dendrimers doped with a phenylboronic derivative at different ratios of -B(OH)₂ groups to amino groups (-NH₂) and one polyethyleneimine (PEI) polymer doped with a phenylboronic acid derivative were used as molecular receptors. The voltammetric glucose detection was based on the difference in the affinity of the tested systems in relation to 2-((ferrocenylmethyl)amino)propane-1,3-diol (Fc-1,3-diol) and glucose. Polymeric phenylboronic compounds were introduced to the electrode surface through an electrodeposition process at a constant potential. The obtained calibration curves were characterized by a wide range of linearity (0.005-100 μM) and low values of the limit of detection reaching even 0.0012 μM. Moreover, the influence of interferents (ascorbic acid, uric acid and fructose) was investigated at two different concentrations. Only fructose had a significant influence on the oxidation signal of ferrocene units, but solely in the case of R-Ph-B(OH)₂ (where R = PEI or PAMAM; Ph - phenyl ring) systems with a low content of boron groups, and these systems form complexes with glucose in a stoichiometric ratio of 1 : 1. The reliability of the results was confirmed by determining the percentage of recovery (added glucose vs. labeled glucose). Most of the results met the acceptance criteria (95%-105%), allowing the developed electrochemical sensors to be successfully used for the analysis of real-life samples.

Electrochemical synthesis and corrosion protection of poly(3-aminophenylboronic acid-co-pyrrole) on mild steel

Synthesis of poly(3-aminophenylboronic acid-co-pyrrole) (p(APBA-co-Py)) is carried out potentiodynamically on a pre-passivated mild steel (MS) surface in an oxalic acid solution containing 3-aminophenylboronic acid (APBA) and pyrrole (Py) monomers. The monomer feed ratio was determined using electrochemical impedance spectroscopy (EIS) and adhesion tests. The p(APBA-co-Py) coating is characterized by electrochemically and spectroscopically comparing with poly(3-aminophenylboronic acid) (p(APBA) and polypyrrole (p(Py) homopolymers. SERS, FTIR, XPS, scanning electron microscopy-wavelength dispersive X-ray and- energy dispersive X-ray spectroscopy results indicate the presence of both APBA and Py segments in the p(APBA-co-Py) backbone. The protective properties of the coating are investigated by Tafel and EIS measurements in a 0.50 M HCl solution. The corrosion resistance of p(APBA-co-Py)-coated MS (66.8 Ω cm²) is higher than that of p(APBA)- and p(Py)-coated, passivated, and uncoated MS. The p(APBA-co-Py) coating embodies the advantageous features of both homopolymers. Py units in p(APBA-co-Py) chains improve the protective property while APBA units carrying the –B(OH)₂ group develop the adhesive property of the layer. EIS results show that the p(APBA-co-Py) coating, due to its homogeneous and compact distribution and the formation of a stable interface, enhanced corrosion resistance of MS by 87.4% for 10 hours in HCl corrosive medium.

Synthesis of poly(3-aminophenylboronic acid-co-pyrrole) (p(APBA-co-Py)) is carried out potentiodynamically on a pre-passivated mild steel (MS) surface in an oxalic acid solution containing 3-aminophenylboronic acid (APBA) and pyrrole (Py) monomers.

Potentiometric detection of glucose based on oligomerization with a diboronic acid using polycation as an indicator

A novel potentiometric sensor for d-glucose (Glu) using 4,4'-biphenyldiboronic acid as a receptor and polyion (poly-N-(3-aminopropyl)methacrylamide, PAPMA) as an indicator is described. The diboronic acid condenses with Glu via its two cis-diol units to form cyclic or linear oligomeric polyanions which can interact electrostatically with PAPMA, thus efficiently decreasing its potentiometric response on a polycation-sensitive membrane electrode. Although d-fructose (Fru), d-galactose (Gal) and d-mannose (Man) show even higher binding affinities to the diboronic acid as compared to Glu, these monosaccharides with only one cis-diol unit cannot oligomerize with the receptor, which efficiently excludes the interferences from the Glu's stereoisomers. The results obtained from blood sample analysis indicate that the proposed sensor is promising for detection of Glu in real-world applications.

Non-Enzymatic Glucose Sensing Based on Incorporation of Carbon Nanotube into Zn-Co-S Ball-in-Ball Hollow Sphere

Zn-Co-S ball-in-ball hollow sphere (BHS) was successfully prepared by solvothermal sulfurization method. An efficient strategy to synthesize Zn-Co-S BHS consisted of multilevel structures by controlling the ionic exchange reaction was applied to obtain great performance electrode material. Carbon nanotubes (CNTs) as a conductive agent were uniformly introduced with Zn-Co-S BHS to form Zn-Co-S BHS/CNTs and expedited the considerable electrocatalytic behavior toward glucose electro-oxidation in alkaline medium. In this study, characterization with scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) was used for investigating the morphological and physical/chemical properties and further evaluating the feasibility of Zn-Co-S BHS/CNTs in non-enzymatic glucose sensing. Electrochemical methods (cyclic voltammetry (CV) and chronoamperometry (CA)) were performed to investigate the glucose sensing performance of Zn-Co-S BHS/CNTs. The synergistic effect of Faradaic redox couple species of Zn-Co-S BHS and unique conductive network of CNTs exhibited excellent electrochemical catalytic ability towards the glucose electro-oxidation, which revealed linear range from 5 to 100 μM with high sensitivity of 2734.4 μA mM^-1 cm^-2, excellent detection limit of 2.98 μM, and great selectivity in the presence of dopamine, uric acid, ascorbic acid, and fructose. Thus, Zn-Co-S BHS/CNTs would be expected to be a promising material for non-enzymatic glucose sensing.

Electrochemical polymerization of poly(aniline-o-anisidine) and its anticorrosion properties

A synthesis of bismuth selenide with a thickness of 3-4 nm on the surface of mica taken as a matrix was investigated using the gas-solid mechanism. Since discovery of two-dimensional atomic crystals of graphene in 2004, scientists have grown interested in exploring methods for synthesis of two-dimensional atomic crystal nanofilms. Among them, of particular interest are sulfides and transition metal selenides, such as molybdenum sulfide, tungsten selenide, bismuth selenide. Bismuth selenide possesses special thermoelectric, photoelectric properties, therefore there are wide possibilities for its use in such areas as thermoelectric devices, photosensitive elements, optical information keepers, etc. In this connection, there are many studies on the search for optimal methods for the synthesis of bismuth selenide. Each of the proposed methods has its own advantages and disadvantages. In the article, a variety of the recently used gas-liquid-solid mechanism (V-L-S) is used as a method for the synthesis of bismuth selenide. When using amorphous silicon dioxide as a matrix, the synthesized bismuth selenide is not uniform, and the synthesis process is uncontrollable. Therefore, in the work fluorinated gold mica was used as a matrix. The effect of temperature, gas feed rate on the size, shape and thickness of the film was investigated.

A Facile Fabrication of a Potentiometric Arrayed Glucose Biosensor Based on Nafion-GOx/GO/AZO

In this study, the potentiometric arrayed glucose biosensors, which were based on zinc oxide (ZnO) or aluminum-doped zinc oxide (AZO) sensing membranes, were fabricated by using screen-printing technology and a sputtering system, and graphene oxide (GO) and Nafion-glucose oxidase (GOx) were used to modify sensing membranes by using the drop-coating method. Next, the material properties were characterized by using a Raman spectrometer, a field-emission scanning electron microscope (FE-SEM), and a scanning probe microscope (SPM). The sensing characteristics of the glucose biosensors were measured by using the voltage–time (V-T) measurement system. Finally, electrochemical impedance spectroscopy (EIS) was conducted to analyze their charge transfer abilities. The results indicated that the average sensitivity of the glucose biosensor based on Nafion-GOx/GO/AZO was apparently higher than that of the glucose biosensor based on Nafion-GOx/GO/ZnO. In addition, the glucose biosensor based on Nafion-GOx/GO/AZO exhibited an excellent average sensitivity of 15.44 mV/mM and linearity of 0.997 over a narrow range of glucose concentration range, a response time of 26 s, a limit of detection (LOD) of 1.89 mM, and good reproducibility. In terms of the reversibility and stability, the hysteresis voltages (V_H) were 3.96 mV and 2.42 mV. Additionally, the glucose biosensor also showed good anti-inference ability and reproducibility. According to these results, it is demonstrated that AZO is a promising material, which could be used to develop a reliable, simple, and low-cost potentiometric glucose biosensor.

Passive and wireless, implantable glucose sensing with phenylboronic acid hydrogel-interlayer RF resonators

A phenylboronic acid-based, hydrogel-interlayer Radio-Frequency (RF) resonator is demonstrated as a highly-responsive, passive and wireless sensor for glucose monitoring. Constructs are composed of unanchored, capacitively-coupled split rings interceded by glucose-responsive hydrogels. Phenylboronic acid-hydrogels exhibit volumetric and dielectric variations in response to environmental glucose concentrations-these are efficiently converted to large shifts in the resonant response of interlayer-RF sensors. These tiny, stretchable and scalable sensors (5 mm × 5 mm x 250 μm) require no microelectronics or power at the sensing node and can be read-out remotely via near-field coupling. Sensors exhibit high sensitivities (~10% shift in resonant frequency-corresponding to 50 MHz-per 150 mg/dL of glucose), possess a limit of detection of 10 mg/dL, and a step response time of approximately 1 h to abrupt shifts in carbohydrate concentration. Notably, these sensors exhibited no signal drift or hysteresis over the time periods characterized herein (45 days at room temperature). We transform sensors into bioelectronic RF reporter-tags via the attachment of a single LED-these remotely report on glucose concentration via emitted light. We anticipate the non-degradative, long-term nature of both RF read-out and phenylboronic acid-based hydrogels will enable biosensors capable of long-term, remote read-out of glucose.

Capacitive Saccharide Sensor Based on Immobilized Phenylboronic Acid with Diol Specificity

A capacitive sensor for saccharide detection is described in this study. The detection is based on selective interaction between diols and aminophenylboronic acid (APBA) immobilized on a gold electrode. Glucose, fructose, and dextran (MW: 40 kDa) were tested with the system over wide concentration ranges (1.0 x 10-8 M - 1.0 x 10-3 M for glucose, 1.0 x 10-8 M - 1.0 x 10-2 M for fructose and 1.0 x 10-10 M - 1.0 x 10-5 M for dextran). The limits of detection (LODs) were 0.8 nM for glucose, 0.6 nM for fructose, and 13 pM for dextran. These data were comparable to the others reported previously. In order to demonstrate glycoprotein detection with the same sensor, human immunoglobulin G (IgG) as well as horseradish peroxidase were used as model analytes. The sensor responded to IgG in the concentration range of 1.0 x 10-13 M - 1.0 x 10-7 M with a LOD value of 16 fM. The performance of the assay of peroxidase was compared to a spectrophotometric assay by determining the enzymatic activity of a captured analyte. The results showed that the method might be useful for label-free, fast, and sensitive detection of saccharides as well as glycoproteins over a wide concentration range.

A molecular dynamics study on glucose molecular recognition by a non-enzymatic selective sensor based on a conducting polymer

Poly(hydroxymethyl-3,4-ethylendioxythiophene) (PHMeDOT), a very electroactive polythiophene derivative bearing a dioxane ring fused onto the thiophene ring and an exocyclic hydroxymethyl substituent, is able to electrocatalyze the oxidation of glucose in the presence of interferents (e.g. dopamine, uric acid and ascorbic acid) without the assistance of an enzymatic catalyst. In this work, after demonstrating that the chronoamperometric response of such polythiophene derivatives allows discrimination of glucose from fructose, the PHMeDOTsugar recognition mechanism has been investigated using atomistic computer simulations. More specifically, molecular dynamics simulations were conducted on model systems formed by a steel surface covered with a nanometric film of PHMeDOT, which was immersed in an aqueous environment with a few explicit sugar molecules (i.e. glucose or fructose). Analyses of the trajectories indicate that glucose interacts with PHMeDOT forming a well-defined network of specific hydrogen bonds. More specifically, glucose prefers to interact as a hydrogen bonding donor using the hydroxyl group tether to the main sugar ring, while PHMeDOT acts as the hydrogen bonding acceptor. Interestingly, (glucose)O-HO(PHMeDOT) interactions involve, as hydrogen bonding acceptors, not only the oxygen atoms of the dioxane ring but also the oxygen atom of the exocyclic hydroxymethyl substituent, which is a differential trend with respect to the other polythiophene derivatives that do not exhibit sensing ability. In contrast, fructose does not present such well-defined patterns of specific interactions, especially those that are distinctive because of the exocyclic hydroxymethyl substituent, making the experimental observations understandable.

Recent advances in electrochemical non-enzymatic glucose sensors - A review

This review encompasses the mechanisms of electrochemical glucose detection and recent advances in non-enzymatic glucose sensors based on a variety of materials ranging from platinum, gold, metal alloys/adatom, non-precious transition metal/metal oxides to glucose-specific organic materials. It shows that the discovery of new materials based on unique nanostructures have not only provided the detailed insight into non-enzymatic glucose oxidation, but also demonstrated the possibility of direct detection in whole blood or interstitial fluids. We critically evaluate various aspects of non-enzymatic electrochemical glucose sensors in terms of significance as well as performance. Beyond laboratory tests, the prospect of commercialization of non-enzymatic glucose sensors is discussed.

Recent progress in electrochemical biosensors based on phenylboronic acid and derivatives

This review provides an overview of recent progress made in the development of electrochemical biosensors based on phenylboronic acid (PBA) and its derivatives. PBAs are known to selectively bind 1,2- and 1,3-diols to form negatively charged boronate esters in neutral aqueous media and have been used to construct electrochemical glucose sensors because of this selective binding. PBA-modified metal and carbon electrodes have been widely studied as voltammetric and potentiometric glucose sensors. In some cases, ferroceneboronic acid or ferrocene-modified phenylboronic acids are used as sugar-selective redox compounds. Another option for sensors using PBA-modified electrodes is potentiometric detection, in which the changes in surface potential of the electrodes are detected as an output signal. An ion-sensitive field effect transistor (FET) has been used as a signal transducer in potentiometric sensors. Glycoproteins, such as glycated hemoglobin (HbA1c), avidin, and serum albumin can also be detected by PBA-modified electrodes because they contain hydrocarbon chains on the surface. HbA1c sensors are promising alternatives to enzyme-based glucose sensors for monitoring blood glucose levels over the preceding 2-3months. In addition, PBA-modified electrodes can be used to detect a variety of compounds including hydroxy acids and fluoride (F(-)) ions. PBA-based F(-) ion sensors may be useful if reagentless sensors can be developed.

A graphene-based affinity nanosensor for detection of low-charge and low-molecular-weight molecules

This paper presents a graphene nanosensor for affinity-based detection of low-charge, low-molecular-weight molecules, using glucose as a representative. The sensor is capable of measuring glucose concentration in a practically relevant range of 2 μM to 25 mM, and can potentially be used in noninvasive glucose monitoring.

Paper membrane-based SERS platform for the determination of glucose in blood samples

In this report, we present a paper membrane-based surface-enhanced Raman scattering (SERS) platform for the determination of blood glucose level using a nitrocellulose membrane as substrate paper, and the microfluidic channel was simply constructed by wax-printing method. The rod-shaped gold nanorod particles were modified with 4-mercaptophenylboronic acid (4-MBA) and 1-decanethiol (1-DT) molecules and used as embedded SERS probe for paper-based microfluidics. The SERS measurement area was simply constructed by dropping gold nanoparticles on nitrocellulose membrane, and the blood sample was dropped on the membrane hydrophilic channel. While the blood cells and proteins were held on nitrocellulose membrane, glucose molecules were moved through the channel toward the SERS measurement area. Scanning electron microscopy (SEM) was used to confirm the effective separation of blood matrix, and total analysis is completed in 5 min. In SERS measurements, the intensity of the band at 1070 cm(-1) which is attributed to B-OH vibration decreased depending on the rise in glucose concentration in the blood sample. The glucose concentration was found to be 5.43 ± 0.51 mM in the reference blood sample by using a calibration equation, and the certified value for glucose was 6.17 ± 0.11 mM. The recovery of the glucose in the reference blood sample was about 88 %. According to these results, the developed paper-based microfluidic SERS platform has been found to be suitable for use for the detection of glucose in blood samples without any pretreatment procedure. We believe that paper-based microfluidic systems may provide a wide field of usage for paper-based applications.

An enzyme-free glucose sensor based on a difunctional diboronic acid for molecular recognition and potentiometric transduction

Based on a diboronic acid for specific recognition of glucose, an enzyme-free potentiometric glucose sensor was developed.

Boronic acids for sensing and other applications - a mini-review of papers published in 2013

Boronic acids are increasingly utilised in diverse areas of research. Including the interactions of boronic acids with diols and strong Lewis bases as fluoride or cyanide anions, which leads to their utility in various sensing applications. The sensing applications can be homogeneous assays or heterogeneous detection. Detection can be at the interface of the sensing material or within the bulk sample. Furthermore, the key interaction of boronic acids with diols allows utilisation in various areas ranging from biological labelling, protein manipulation and modification, separation and the development of therapeutics. All the above uses and applications are covered by this mini-review of papers published during 2013.