Electrochemical Sensing of Biotin Using Nafion-Modified Boron-Doped Diamond Electrode

Electrochemical sensor for ultrasensitive sensing of biotin based on heme conjugated with gold nanoparticles and its electrooxidation mechanism

We report the fabrication of a facile sensor using heme conjugated with gold nanoparticles (AuNPs) in situ on a glass carbon electrode (GCE) for the ultrasensitive determination of biotin without antibody or streptavidin. The use of heme and AuNPs as dual amplifiers allows a very broad detection range from 0.0050 to 50.0000 μmol·L-1 and a very low detection limit of 0.0016 μmol·L-1. The mechanistic aspects were elucidated using electrochemical analyses and frontier orbital calculations showing that the electrooxidation of biotin involves a one-electron and a one-proton transfer, generating biotin sulfoxide. The heme/AuNPs/GCE sensor exhibited excellent selectivity, reproducibility and stability, indicating high robustness. The recovery was between 97.20 and 105.70% with RSD less than 8.71%, suggesting good practicability. Our studies demonstrate that this approach can be used to detect and quantify biotin in a range of foods, including milk, infant formula, flour, orange juice, mango juice, egg white and egg yolk. Furthermore, all measurements do not require any intricate preparation or pre-treatment of the foods, thus representing a great potential for point-of-care testing.

Biotinylated Quinone as a Chemiluminescence Sensor for Biotin-Avidin Interaction and Biotin Detection Application

Biotin, or vitamin B7, is essential for metabolic reactions. It must be obtained from external sources such as food and biotin/vitamin supplements because it is not biosynthesized by mammals. Therefore, there is a need to monitor its levels in supplements. However, biotin detection methods, which include chromatographic, immune, enzymatic, and microbial assays, are tedious, time-consuming, and expensive. Thus, we synthesized a product called biotin-naphthoquinone, which produces chemiluminescence upon its redox cycle reaction with dithiothreitol and luminol; then it was used as a chemiluminescence sensor for biotin-avidin interaction. When a quinone biotinylated compound binds avidin, the chemiluminescence decreases noticeably due to the proximity between quinone and avidin, and when free biotin is added in a competitive assay, the chemiluminescence returns. The chemiluminescence is regained as the free biotin displaces biotinylated quinone in its complex with avidin, freeing biotin-naphthoquinone. Many experiments, including the use of a biotin-free quinone, proved the competitive nature of the assay. The competitive assay method used in this study was linear in the range of 1.0-100 µM with a detection limit of 0.58 µM. The competitive chemiluminescence assay could detect biotin in vitamin B7 tablets with good recovery of 91.3 to 110% and respectable precision (RSD < 8.7%).

Different Aspects of the Voltammetric Detection of Vitamins: A Review

Vitamins comprise a group of organic chemical compounds that contribute significantly to the normal functioning of living organisms. Although they are biosynthesized in living organisms, some are also obtained from the diet to meet the needs of organisms, which is why they are characterized as essential chemical compounds. The lack, or low concentrations, of vitamins in the human body causes the development of metabolic dysfunctions, and for this reason their daily intake with food or as supplements, as well as the control of their levels, are necessary. The determination of vitamins is mainly accomplished by using analytical methods, such as chromatographic, spectroscopic, and spectrometric methods, while studies are carried out to develop new and faster methodologies and techniques for their analysis such as electroanalytical methods, the most common of which are voltammetry methods. In this work, a study is reported that was carried out on the determination of vitamins using both electroanalytical techniques, the common significant of which is the voltammetry technique that has been developed in recent years. Specifically, the present review presents a detailed bibliographic survey including, but not limited to, both electrode surfaces that have been modified with nanomaterials and serve as (bio)sensors as well as electrochemical detectors applied in the determination of vitamins.

Fabrication and Optimization of Nafion as a Protective Membrane for TiN-Based pH Sensors

In this study, a solid-state modified pH sensor with RF magnetron sputtering technology was developed. The sensor consists of an active electrode consisting of a titanium nitride (TiN) film with a protective membrane of Nafion and a reference glass electrode of Ag/AgCl. The sensitivity of the pH sensor was investigated. Results show a sensor with excellent characteristics: sensitivity of 58.6 mV/pH for pH values from 2 to 12, very short response time of approximately 12 s in neutral pH solutions, and stability of less than 0.9 mV in 10 min duration. Further improvement in the performance of the TiN sensor was studied by application of a Nafion protective membrane. Nafion improves the sensor sensitivity close to Nernstian by maintaining a linear response. This paves the way to implement TiN with Nafion protection to block any interference species during real time applications in biosensing and medical diagnostic pH sensors.

Streptavidin Fe2O3-gold nanoparticles functionalized theranostic liposome for antibiotic resistant bacteria and biotin sensing

Novel methods of sensing and treatment required to elicit potent humoral and cellular immune responses. Here, Streptavidin functionalized α-Fe2O3-Au nanoparticles (STV-Mag) loaded cationic carbomate cholesterol is used as a carrier to release antibacterial thymol drug for Staphylococcus aureus (S. aureus) infected Caenorhabditis elegans (C. elegans). Pertaining to theranostic applications, efficient antimicrobial activity, and non-stimulated drug release and biotin dependent S. aureus growth were studied in-vivo. While STV-Mag was tethered on mercaptobenzoic acid (MBA) molecular cushion for label free streptavidin-biotin electrochemical sensing, the STV-Mag-carbomate cholesterol (STV-Mag-cCHOL liposome) vesicle with loaded drug was tethered on MBA for non-stimulant drug release through specific cholesterol-S. aureus interaction and confirmed electrochemically. Selectivity was confirmed using other pathogens, E. coli, Proteus and Enterococcus bacterium through antimicrobial studies along with S. aureus. The biotin sensing showed linear range from 10-15 to 10-3 M, which was not obtained by conventional methods. Fourier-Transform Infra-red (FT-IR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques were used to characterize the nanoparticulate system.

Insights into the Design of An Enzyme Free Sustainable Sensing Platform for Efavirenz

In this study, a new hybrid sensor was developed using titanium oxide nanoparticles (TiO2-NPs) and nafion as an anchor agent on a glassy carbon electrode (GCE/TiO2-NPs-nafion) to detect efavirenz (EFV), an anti-HIV medication. TiO2-NPs was synthesized using Eucalyptus globulus leaf extract and characterized using ultraviolet–visible spectroscopy (UV–VIS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive spectroscopy (EDS). The electrochemical and sensing properties of the developed sensor for EFV were assessed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The current response of GCE/TiO2-NPs-nafion electrode towards the oxidation of EFV was greater compared to the bare GCE and GCE/TiO2-NPs electrodes. A linear dynamic range of 4.5 to 18.7 µM with 0.01 µM limit of detection was recorded on the electrode using differential pulse voltammetry (DPV). The electrochemical sensor demonstrated good selectivity and practicality for detecting EFV in pharmaceuticals (EFV drugs) with excellent recovery rates, ranging from 92.0–103.9%. The reactive sites of EFV have been analyzed using quantum chemical calculations based on density functional theory (DFT). Monte Carlo (MC) simulations revealed a strong electrostatic interaction on the substrate-adsorbate (GCE/TiO2-NPs-nafion-EFV) system. Results show good agreement between the MC computed adsorption energies and the experimental CV results for EFV. The stronger adsorption energy of nafion onto the GCE/TiO2-NPs substrate contributed to the catalytic role in the signal amplification for sensing of EFV. Our results provide an effective way to explore the design of new 2D materials for sensing of EFV, which is highly significant in medicinal and materials chemistry.

Application of HRP-streptavidin bionanoparticles for potentiometric biotin determination

Biotin is widely used in infant formula to prevent biotin deficiency of newborn babies and in beauty products as nutritional supplements for coenzymatic functions and having strong nails, shiny hair, and skin over the last few years. There is a need for the development of a fast, simple and reusable assay method to perform biotin determination at very low concentrations. Biotin determination has achieved with a prepared potentiometric biotin sensor that has a very wide concentration range (10-15M-10-7M) and a lower detection limit (0.3 10-15M) with a very good regression coefficient (0.9925). A quick response (7 min), good accuracy (recovery 100.4-103.7%), reproducible, reusable (10 times), and long-term stability (3 months) have been obtained using the prepared potentiometric sensor. The obtained results have proved that the prepared potentiometric sensor can be used for biotin determination in real samples.

Avidin-Biotin Technology in Gold Nanoparticle-Decorated Graphene Field Effect Transistors for Detection of Biotinylated Macromolecules with Ultrahigh Sensitivity and Specificity

The strong and specific noncovalent interaction between avidin and biotin is widely exploited in different types of enzyme-linked immunosorbent assay kits, labeled immunosensors, and polymer-based sensing devices for the detection of different biomarkers specific to different diseases such as cancer and influenza. Here, we employed the avidin-biotin technology in a novel gold nanoparticle-decorated graphene field-effect transistor (AuNP-GFET) and demonstrated the specific detection of the biotinylated macromolecules such as biotinylated proteins and nucleotides in the sub-picomolar (pM) range. The AuNP-GFET was constructed by fabricating six pairs of interdigital electrodes on graphene transferred on a SiO2/Si substrate. The sensing performance of AuNP-GFET was characterized by the real-time two-terminal electrical current measurement upon injection of the analyte solution into a silicone pool preattached onto the electrodes. Avidin, a tetrameric biotin-binding protein with strong affinity and specificity, immobilized on AuNP-decorated single-layer graphene, was used as the sensing platform and transduced the electrical signal upon binding to the analyte macromolecules. The sensing capability of the AuNP-GFET was tested with the biotinylated protein A. Sensitivity of the present biosensor was estimated to be ∼0.4 pM. The specificity and applicability of the biosensor were confirmed using both synthetic and real samples. Because the biotin label can retain its binding capability to avidin with strong affinity and specificity even after conjugating with varieties of proteins and nucleotides, the present AuNP-GFET biosensor is expected to promote the research in developing different biosensors.

Recent Advances in Electrochemical Sensors and Biosensors for Detecting Bisphenol A

In recent years, several studies have focused on environmental pollutants. Bisphenol A (BPA) is one prominent industrial raw material, and its extensive utilization and release into the environment constitute an environmental hazard. BPA is considered as to be an endocrine disruptor which mimics hormones, and has a direct relationship to the development and growth of animal and human reproductive systems. Moreover, intensive exposure to the compound is related to prostate and breast cancer, infertility, obesity, and diabetes. Hence, accurate and reliable determination techniques are crucial for preventing human exposure to BPA. Experts in the field have published general electrochemical procedures for detecting BPA. The present timely review critically evaluates diverse chemically modified electrodes using various substances that have been reported in numerous studies in the recent decade for use in electrochemical sensors and biosensors to detect BPA. Additionally, the essential contributions of these substances for the design of electrochemical sensors are presented. It has been predicted that chemically modified electrode-based sensing systems will be possible options for the monitoring of detrimental pollutants.

Graphene field-effect transistor biosensor for detection of biotin with ultrahigh sensitivity and specificity

Because avidin and biotin molecules exhibit the most specific and strongest non-covalent interaction, avidin-biotin technology is widely used in ELISA (enzyme-linked immunosorbent assay) kits for the detection of different bio-macromolecules linked to different diseases including cancer and influenza. Combining the outstanding electrical conductivity (200,000 cm²V^-1s^-1) of graphene with the unique avidin and biotin interaction, we demonstrate a novel graphene field-effect transistor (GFET) biosensor for the quantitative detection of bio-macromolecules. The GFET consists of six pairs of interdigital Cr/Au electrodes supported on Si/SiO₂ substrate with an avidin immobilized single layer graphene channel as the sensing platform. By monitoring the real time current change upon the addition of biotin solution in bovine serum albumin (BSA) in the silicone pool preformed onto the GFET, the lowest detectable biotin concentration is estimated to be 90 fg/ml (0.37 pM). The specificity of the GFET is confirmed both by controlled and real sample measurements. From the magnitude of current change upon the addition of different concentrations of biotin solutions, the dissociation constant K_d is estimated to be 1.6 × 10^-11 M. Since biotin is capable of conjugating with proteins, nucleotides and other bio-macromolecules without altering their properties, the present GFET sensor with its ultra-high sensitivity (0.37 pM) and specificity can be tailored to the rapid point-of-care detection of different types of desired biomolecules at very low concentration level through biotinylation as well as the exogenous biotin in blood serum.

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Combining the outstanding electrical conductivity of graphene with the unique interaction between avidin and biotin, a novel graphene field-effect transistor (GFET) biosensor for quantitative detection of bio-macromolecules is demonstrated.

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The present biosensor is capable of detecting the biotin with the sensitivity of 90 fg/ml (~0.37 pM) and high specificity.

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Since the biotin is capable of conjugating with protein, nucleotide and other bio-macromolecules without affecting their properties, the present GFET sensor can be tailored to various medical applications.

Chemistry of Biotin-Streptavidin and the Growing Concern of an Emerging Biotin Interference in Clinical Immunoassays

Overconsumption of biotin (5-100 mg daily) as a supplement by the general population poses a significant problem for clinical immunoassays (IAs) based on biotin-streptavidin (SA) interactions. This affinity pair has been exploited in immunoassays because of its avidity, sensitivity, specificity, and stability. The elevated biotin level in plasma varies from patient to patient, and its severe interference cannot easily be predicted and quantified. Thus, immunoassay manufacturers must investigate the biotin interference in the developed immunoassays to satisfy the threshold of 3510 ng/mL (14 367 nM), as stipulated by the FDA. There is no concrete solution to circumvent the biotin interference without extra costs and technical difficulties, albeit different strategies have been attempted. They include the IA format with biotinylated reagents prebound to streptavidin, the removal of biotin from the specimen, sample treatment, and biotin interference-free assays. The general public has been instructed to stop taking biotin supplements for 48 h or even weeks before the test, depending on the specific test, dose, and frequency of biotin uptake. As lab-based techniques cannot accommodate an enormous number of public samples, a rapid analytical procedure for biotin is urgently needed to quantify for its interference in immunoassays.