Preparation Of Biosensor Research Articles

Synthesis of 1,3-di(4-amino-1-pyridinium)propane ionic liquid functionalized graphene nanosheets and its application in direct electrochemistry of hemoglobin

1,3-Di(4-amino-1-pyridinium)propane tetrafluoroborate (DAPPT) ionic liquid was successfully synthesized, and was used as a modifier to functionalize graphene nanosheets through covalent binding of amino groups and epoxy groups in an alkaline solution. The as-prepared graphene-DAPPT nanosheets (Gr-DAPPT) were confirmed with transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV/vis and FTIR spectroscopy. A biocompatible platform based on Gr-DAPPT was constructed for the immobilization of hemoglobin (Hb) through a cross-linking step with chitosan and glutaraldehyde. The direct electron transfer and bioelectrocatalytic reaction of Hb immobilized on Gr-DAPPT surface were achieved. A pair of reversible redox peaks of hemoglobin was observed, and bioelectrocatalytic activity toward the reduction of H2O2 was also demonstrated, displaying a potential application for the fabrication of novel biosensors to sense H2O2. Such results indicated that Gr-DAPPT based interface would be a promising platform for biomacromolecular immobilization and biosensor preparation.

Immobilization Method to Preserve Enzyme Specificity in Biosensors: Consequences for Brain Glutamate Detection

Microelectrode biosensors are a promising technique to probe the brain interstitial fluid and estimate the extracellular concentration of neurotransmitters like glutamate. Their selectivity is largely based on maintaining high substrate specificity for the enzymes immobilized on microelectrodes. However, the effect of enzyme immobilization on substrate specificity is poorly understood. Furthermore, the accuracy of biosensor measurements for brain biological extracts has not been reliably established in comparison with conventional analytical techniques. In this study, microelectrode biosensors were prepared using different enzyme immobilization methods, including glutaraldehyde, a conventional cross-linker, and poly(ethylene glycol) diglycidyl ether (PEGDE), a milder immobilization reagent. Glutaraldehyde, but not PEGDE, significantly decreased the apparent substrate specificity of glutamate and glucose oxidase. For glutaraldehyde prepared biosensors, detection of secondary substrates by glutamate oxidase increased, resulting in a significant overestimate of glutamate levels. This effect was not observed with PEGDE-based biosensors, and when brain microdialysates were analyzed, the levels of glutamate detected by biosensors were consistent with those detected by capillary electrophoresis. In addition, basal concentrations of glutamate detected in vivo were approximately 10-fold lower than the levels detected with glutaraldehyde-based biosensors (e.g., 1.2 μM vs 16 μM, respectively). Overall, enzyme immobilization can significantly impact substrate specificity, and PEGDE is well-suited for the preparation of stable and selective biosensors. This development questions some of the previous biosensor studies aimed at detecting glutamate in the brain and opens new possibilities for specific neurotransmitter detection.


 Application of Gold Nanoparticles in Biomedical Researches and Diagnosis

Gold nanoparticles have been widely used in biomedical research and diagnosis for their good biocompatibility, high surface areas, nontoxic and unique physicochemical properties. This article reviews the applications of gold nanoparticles in the detection of pathogens, proteins, toxic substances, and drug analyses, and in the preparation of biosensors, treatment of disease, and etiological analysis. The application of gold nanoparticles will have broader applications in biomedical research and diagnosis along with a deeper research into AuNPs and more findings in its novel special properties.

Photoelectrochemically active species and photoelectrochemical biosensors

Photoelectrochemical biosensors developed from solar cells have received increasing attention due to their desirable sensitivity and better analytical performance. In recent decades, much attention has been paid to the preparation of photoelectrochemical biosensors. This paper aims to provide an overview on the development of photosensitizers, including the sensing principle of photoelectrochemical biosensors and a special kind of photoelectrochemical biosensor without external irradiation. The latest developments and applications are also included.

Crumpled reduced graphene oxide-polyamidoamine dendrimer hybrid nanoparticles for the preparation of an electrochemical biosensor.

Reduced graphene nanoparticles were prepared from graphene oxide through a two-step covalent modification approach. Graphene oxide was first enriched with reactive epoxy groups by anchoring (3-glycidyloxypropyl)trimethoxysilane at the hydroxyl groups located on the nanocarbon basal plane. Modified graphene oxide was further cross-linked and partially reduced by treatment with the fourth-generation ethylenediamine core polyamidoamine G-4 dendrimer producing graphene nanoparticles with crumpled paper-like morphology. This graphene derivative was employed as a coating material for glassy carbon electrodes and the nanostructured electrode was tested for the preparation of electrochemical biosensors by immobilizing the enzyme tyrosinase through cross-linking with glutaraldehyde. This bioelectrode showed excellent electroanalytical behavior for catechol with a fast response in about 6 s, linear range of 10 nM to 22 μM, sensitivity of 424 mA M-1, and low detection limit of 6 nM. The enzyme biosensor also showed high stability when stored at 4 °C under dry and wet conditions.

Preparation of a new electrochemical biosensor for single base mismatch detection in DNA

In this study, a sandwich-type electrochemical DNA hybridization biosensor for the detection of single base mismatches (SBMs) has been described. 2,5-Dihydroxybenzoic acid (DHBA) is employed as a new redox probe in this study. For construction of the biosensor, thiolated capture DNA is self-assembled on a gold electrode surface and hybridized with one region of a target DNA sequence. Subsequently, a signaling amino-labeled probe DNA is hybridized to a second region of the target DNA to complete the DNA double-helix self-assembled monolayer (SAM). Finally DHBA is covalently attached to the signaling probe DNA using the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHS) cross-linking reaction. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) are employed to characterize the modification steps. The electrochemical signal of DHBA was followed for studying different types of mismatches (GA, GT, TT, CA), both near the electrode surface (N-type) and far from it (F-type). The presence of a SBM leads to a considerable decrease in the electrochemical signal of DHBA compared to that of complementary DNA (cDNA), which makes the detection of mismatches (including thermodynamically stable GA mismatches) possible. The redox signal of DHBA was compared with that of methylene blue (MB) as a well-known and standard redox reporter in DNA biosensors. The results showed that for an N-type SBM, which is located between the electrode and the site of intercalation, the redox signal of MB switches off, whereas for an F-type SBM, which is located above the site of intercalation, electrons flow from the Au electrode to the intercalated MB, and hence the biosensor could not distinguish the presence and absence of an SBM. The proposed biosensor is straightforward with no need for target labeling, and is sensitive enough to detect SBMs independent of their position in DNA double helix.

Effect of Glutaraldehyde on the Conformational Properties of Kluyveromyces lactis β-Galactosidase and Its Application to Sucrose Biosensor Preparation

Effect of Glutaraldehyde on the Conformational Properties of Kluyveromyces lactis β-Galactosidase and Its Application to Sucrose Biosensor Preparation

Electrochemical biosensor based on graphene, Mg2Al layered double hydroxide and hemoglobin composite

A graphene (GR) and Mg2Al layered double hydroxide (LDH) composite was prepared and used for the immobilization of hemoglobin (Hb) on a carbon ionic liquid electrode (CILE) to obtain an electrochemical biosensor. Morphology of the materials was analyzed by scanning electron microscopy and transmission electron microscopy. Spectroscopic experiments were performed to characterize the conformational changes of Hb in the GR-LDH membrane. Electrochemical investigation showed a pair of well-defined quasi-reversible redox peaks appeared with redox peak potentials as −0.145V (Epa) and −0.248V (Epc) in phosphate buffer solution (0.1molL−1, pH 3.0) at the scan rate of 100mVs−1, which indicated that direct electrochemistry of Hb was realized on the modified electrode. So the presence of GR-LDH composite could facilitate the electron transfer rate between CILE and the electroactive center of Hb. The immobilized Hb in GR-LDH modified electrode exhibited excellent electrocatalytic reduction to trichloroacetic acid in the concentration range from 1.6 to 25.0mmolL−1 with the detection limit as 0.534mmolL−1 by cyclic voltammetry, which indicated the successfully preparation of a third-generation electrochemical biosensor.

One-pot preparation of glucose biosensor based on polydopamine–graphene composite film modified enzyme electrode

Abstract A green, facile and low cost approach was developed to fabricate a glucose biosensor based on polydopamine–graphene hybrid film modified glucose oxidase enzyme electrode. Dopamine, graphene oxide and glucose oxidase were mixed and casted on Au electrode, and after electrochemical processing, polydopamine, glucose oxidase and graphene modified electrode was obtained. The as-synthesized enzyme electrodes were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared and X-ray diffraction spectra. The biosensor showed the excellent amperometric biosensing performances, e.g., a high detection sensitivity (28.4 μA mM−1cm−2), a low limit of detection (0.1 μm), a short response periods (

GOLD NANOPARTICLES-BASED BIOSENSORS FOR BIOMEDICAL APPLICATION

Gold nanoparticles are the most extensively studied nanomaterials for biomedical application due to their unique properties, such as rapid and simple synthesis, large surface area, strong adsorption ability and facile conjugation to various biomolecules. The remarkable photophysical properties of gold nanoparticles have provided plenty of opportunities for the preparation of gold nanoparticles-based optical biosensors, while the excellent biocompatibility, conductivity, catalytic properties and large surface-to-volume ratio have facilitated the application of gold nanoparticles in the construction of electrochemical biosensors. In this review, we mainly detail the gold nanoparticles-based optical and electrochemical biosensors for biomedical application in the recent two years, which have exhibited greatly enhanced analytical performances in the detection of DNA, proteins and some important small molecules.

Reduced steric hindrance and optimized spatial arrangement of carbohydrate ligands in imprinted monolayers for enhanced protein binding

Imprinted monolayers provide several advantages over bulk imprinting methods. This is especially important for large templates such as proteins. Concanavalin A (Con A)-imprinted binary monolayers consisting of glycolipids with oligo(ethylene glycol) (OEG) spacers and zwitterionic phospholipids (DPPC) were constructed and investigated. The shorter phosphorylcholine (PC) headgroups with an almost flat-on orientation in the binary monolayers gave rise to reduced steric hindrance favorable to the accommodation of Con A with greater ease and facilitated the access of the OEG-linked mannose moieties for enhanced protein binding. Further enhanced binding resulted from optimized spatial rearrangement of the glycolipids at the air–water interface directed by Con A in the subphase to create bivalent binding sites and to minimize steric crowding of neighboring mannose ligands. The combination of the exposed carbohydrate ligands from biologically inert surfaces and the optimized ligand arrangement is the most reasonable solution to enhancement of protein affinity. The bivalent carbohydrate binding sites protruding from the imprinted monolayers were created to be complementary to the Con A binding pockets. This strategy generates tailor-made surfaces with enhanced protein binding and opens the possibility of controlled assembly of intellectual biomaterials and preparation of biosensors.

An Electrochemical Hydrogen Peroxide Biosensor Based on Polydopamine-Entrapped G-Quadruplex-Hemin DNAzyme

The complex of G-quadruplex-hemin, named peroxidase-mimicking DNAzyme, shows a catalytic activity towards the electro-reduction of hydrogen peroxide. Although DNAzyme is popular for the preparation of colorimetric biosensors for hydrogen peroxide, it is rarely used as a catalyst in the assembly of electrochemical biosensors. Meanwhile, it is of significance to develop novel methods in immobilizing DNA for the purpose of fabrication of DNA-based biosensors. In this study, an electrochemical hydrogen peroxide biosensor was successfully constructed using polydopamine-entrapped G-quadruplex-hemin DNAzyme. G-quadruplex-hemin complex was achieved by mixing DNA and hemin. After the physical adsorption of DNAzyme on a glassy carbon electrode, a droplet of 10 μL containing 5 g L−1 dopamine in PBS (pH 8.0) was then cast onto the surface. Dopamine was oxidized by oxygen in air to form polydopamine, realizing the immobilization of DNAzyme. The influence of DNA sequence on the performance of the biosensor is investigated and different conformation-dependent response from electrochemical to optical sensors was observed. The proposed biosensor shows a linear range with the concentration from 10 μM to 1.5 mM and a detection limit of 2.2 μM for hydrogen peroxide. The results demonstrated the possibility of enzyme immobilization on an electrode through polydopamine and the substitution of G-quadruplex-hemin DNAzyme for natural enzyme.

Preparation and electrochemical application of a new biosensor based on plant tissue/polypyrrole for determination of acetaminophen

Banana tissue containing polyphenol oxidase was incorporated into polypyrrole matrix to make a biosensor for the analysis of acetaminophen (ACT). The electrocatalytic behaviour of oxidized acetaminophen was studied at the surface of the biosensor, using various electrochemical methods. The advantages of this biosensor for the determination of acetaminophen are excellent catalytic activity, good detection limit and high exchange current density. The electrochemical and structural properties of the electrode were assessed using cyclic voltammetry, differential voltammetry, chronoamperometric techniques. The analytical properties (sensitivity, I p ) of this biosensor increased with plant tissue loading. Also this new biosensor was successfully applied for determination of acetaminophen in biologic samples.

Simultaneous Measurement of Mechanical and Surface Properties in Thermoresponsive, Anchored Hydrogel Films

Hydrogel films have been used extensively in the preparation of biosensors and biomedical devices. The characteristics of the aqueous interface of the polymer layer are significant for the biosensor or device function; likewise, the changing mechanical properties of thermoresponsive polymers are an important feature that affects the polymer behavior. Atomic force microscopy was used here to characterize both the surface and the mechanical properties of polymeric hydrogel films prepared from a thermoresponsive terpolymer of N-isopropylacrylamide and acrylic acid with benzophenonemethacrylate as a photoreactive cross-linker comonomer. The force-distance curves thus obtained were analyzed to assess both the surface forces and the mechanical response that were associated with the hydrogel. These properties were investigated as a function of temperature, in water and in Tris buffer, for different degrees of polymer cross-linking. For samples in water, the distance over which the surface forces were effective was found to remain constant as the temperature was increased from 26 to 42 °C, even though the mechanical response indicated that the samples had been heated past the lower critical solution temperature, or LCST. The bulk of the polymer becomes less soluble above the LCST, although this does not seem to affect the surface properties. This may be due to the segregation of the acrylic acid-rich polymer segments near the gel surface, which is in agreement with reports for related systems.

Supramolecular Immobilization of Xanthine Oxidase on Electropolymerized Matrix of Functionalized Hybrid Gold Nanoparticles/Single-Walled Carbon Nanotubes for the Preparation of Electrochemical Biosensors

Glassy carbon electrodes modified with single-walled carbon nanotubes and a three-dimensional network of electropolymerized Au nanoparticles capped with 2-mercaptoethanesulfonic acid, p-aminothiophenol, and 1-adamantanethiol were used as hybrid electrochemical platforms for supramolecular immobilization of a synthesized artificial neoglycoenzyme of xanthine oxidase and β-cyclodextrin through host-guest interactions. The ensemble was further employed for the bioelectrochemical determination of xanthine. The biosensor showed fast amperometric response within 5 s and a linear behavior in the 50 nM to 9.5 μM xanthine concentration range with high sensitivity, 2.47 A/(M cm(2)), and very low detection limit of 40 nM. The stability of the biosensor was significantly improved and the interferences caused by ascorbic and uric acids were noticeably minimized by coating the electrode surface with a Nafion thin film.

Enzyme biosensor for androsterone based on 3α-hydroxysteroid dehydrogenase immobilized onto a carbon nanotubes/ionic liquid/NAD+ composite electrode

A 3α-hydrosteroid biosensor for androsterone determination has been prepared by immobilizing the enzyme 3α-hydroxysteroid dehydrogenase (3α-HSD) in a composite electrode platform constituted of a mixture of multi-walled carbon nanotubes (MWCNTs), octylpyridinium hexafluorophosphate (OPPF6) ionic liquid and NAD+ cofactor. This configuration allowed the fast, sensitive and stable electrochemical detection of the NADH generated in the enzyme reaction. All the experimental variables involved in the preparation and performance of the enzyme biosensor were optimized. Amperometry in stirred solutions at +400mV provided a linear calibration plot for androsterone in the 0.5–10μM concentration range with a slope value more than 200-times higher than that previously reported. The detection limit achieved was 0.15μM and a low value of the apparent Michaelis–Menten constant (KappM), 36.0μM, similar to that reported for the enzyme in solution, was calculated. The 3α-HSD/MWCNTs/OPPF6/NAD+ biosensor provided good results in the determination of androsterone in spiked human serum samples.

Preparation and Characterization of an Electrogenerated Chemiluminescence Sensor by Electrochemical Grafting of 4-Nitrophenyl Diazonium Salts Onto a Glass Carbon Electrode

An ECL sensor was fabricated by immobilization of a tris(2,2'-bipyridyl)ruthenium (II) complex (Ru(bpy)3(2+)) to an amine group-modified GC electrode (NH2-GC electrode). Here, the NH2-GC electrode was prepared by electrochemical reduction of a nitro group-modified GC electrode in 0.1 M KCl ethanol solution under H2 gas, which was followed by electrochemical grafting of 4-nitrophenyl diazonium salts in 0.1 M NBu4BF4 acetonitrile solution onto the GC electrode. The prepared ECL sensor was successfully confirmed via cyclic voltammetry, contact angle, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and ECL spectrometry. The contact angle for the surface of the GC electrode, NO2-GC electrode, and NH2-GC electrod was 88.4 degrees, 67.4 degrees, and 52.4 degrees, respectively. The stability of the ECL sensor was investigated under continuous cyclic potential scanning for 55 cycles and the ECL intensity remained at 55%. The prepared ECL electrode can be expected to immobilize enzymes for preparation of the ECL biosensor to detect target molecules.

Effective surface modification of gold nanorods for localized surface plasmon resonance-based biosensors

This paper presents a novel, pH-mediated protocol for the surface modification of gold nanorods (GNRs), which provides a robust platform for the assembly of localized surface plasmon resonance (LSPR)-based sensors, by facilitating functionalization at the surface of the nanoparticles. This is achieved by replacing the surface bilayer of cetyltrimethylammonium bromide (CTAB) with 11-mercaptoundecanoic acid (MUA) at alkaline pH after seed-mediated growth of GNRs. This method fully exploits the characteristics of MUA (i) the carboxylic acid functionality enables ligand exchange in an aqueous environment; (ii) the hydrophobic nature of the molecule stabilizes the nanorods and prevents aggregation via a self-assembled monolayer and (iii) the sulfur moiety binds to the gold surface. Critically, this procedure also simplifies subsequent functionalization, overcoming the limitation arising from commonly used CTAB-only preparation. XPS (X-ray photoelectron spectroscopy) was used to confirm the ligand exchange at the surface of the GNRs. The surface modification facilitates the preparation of a LSPR-based biosensor based on human IgG for the detection of anti-human IgG and a detection limit of 0.4nM was observed.

A conducting polymer with benzothiadiazole unit: Cell based biosensing applications and adhesion properties

Poly(4,7-di(2,3)-dihydrothienol[3,4-b][1,4]dioxin-5-yl-benzo[1,2,5]thiadiazole) (PBDT) was electrochemically deposited on graphite electrodes and used as a matrix for microbial biosensing studies. Moreover, protein adsorption property of the surface was investigated using bovine serum albumin (BSA). For the biosensor preparation, after electrochemical deposition of the polymeric matrix, Gluconobacter oxydans cells were immobilized on the modified electrode. Glucose was used as the substrate and biosensor response was followed successfully at −0.7V vs Ag/AgCl due to the respiratory activity of the cells which is directly proportional with the substrate concentration. Characterizations were carried out in terms of several parameters such as operational and storage stabilities and surface morphologies. Finally, the effect of antimicrobial agent on the cell based response was tested. As a matrix, conducting polymers enable the preparation of sensitive and stable electrochemical microbial biosensors.

Mineral surface–organic matter interactions: basics and applications

The ability to control the binding of biological and organic molecules to a crystal surface is central in several fields; for example, in biotechnology, catalysis, molecular microarrays, biosensors preparation and environmental sciences. The nano-morphology and nanostructure at the surface may have physico-chemical properties that are very different from those of the underlying mineral substrate. Recent developments in scanning probe microscopy (SPM) have widened the spectrum of possible investigations that can be performed at the nanometric level on the surface of minerals. They range from the study of physical properties such as surface potential, electric field topological determination, Brønsted–Lowry site distributions, to chemical and spectroscopic analysis in air, in liquid or in gaseous environments. After an introduction to SPM modes of operation and new SPM-based technological developments, we will present recent examples of applications in the study of interactions between organic matter and mineral surface and report on the advances in knowledge that have been made by the use of scanning probe microscopy.