The preparation of reagentless electrochemical immunosensor based on a nano-gold and chitosan hybrid film for human chorionic gonadotrophin

Advances on Hormones and Steroids Determination: A Review of Voltammetric Methods since 2000

This article presents advances in the electrochemical determination of hormones and steroids since 2000. A wide spectrum of techniques and working electrodes have been involved in the reported measurements in order to obtain the lowest possible limits of detection. The voltammetric and polarographic techniques, due to their sensitivity and easiness, could be used as alternatives to other, more complicated, analytical assays. Still, growing interest in designing a new construction of the working electrodes enables us to prepare new measurement procedures and obtain lower limits of detection. A brief description of the measured compounds has been presented, along with a comparison of the obtained results.

Novel Regeneration Approach for Creating Reusable FO-SPR Probes with NTA Surface Chemistry

To date, surface plasmon resonance (SPR) biosensors have been exploited in numerous different contexts while continuously pushing boundaries in terms of improved sensitivity, specificity, portability and reusability. The latter has attracted attention as a viable alternative to disposable biosensors, also offering prospects for rapid screening of biomolecules or biomolecular interactions. In this context here, we developed an approach to successfully regenerate a fiber-optic (FO)-SPR surface when utilizing cobalt (II)-nitrilotriacetic acid (NTA) surface chemistry. To achieve this, we tested multiple regeneration conditions that can disrupt the NTA chelate on a surface fully saturated with His6-tagged antibody fragments (scFv-33H1F7) over ten regeneration cycles. The best surface regeneration was obtained when combining 100 mM EDTA, 500 mM imidazole and 0.5% SDS at pH 8.0 for 1 min with shaking at 150 rpm followed by washing with 0.5 M NaOH for 3 min. The true versatility of the established approach was proven by regenerating the NTA surface for ten cycles with three other model system bioreceptors, different in their size and structure: His6-tagged SARS-CoV-2 spike fragment (receptor binding domain, RBD), a red fluorescent protein (RFP) and protein origami carrying 4 RFPs (Tet12SN-RRRR). Enabling the removal of His6-tagged bioreceptors from NTA surfaces in a fast and cost-effective manner can have broad applications, spanning from the development of biosensors and various biopharmaceutical analyses to the synthesis of novel biomaterials.

Development of a Novel Nanocomposite Based on Reduced Graphene Oxide/Chitosan/Au/ZnO and Electrochemical Sensor for Determination of Losartan

Background:

Hypertension is a major risk for morbidity and mortality, while hypertension is associated with cardiovascular disease and organ damage. Recent research efforts have focused on the development of highly selective angiotensin receptor blockers. In which losartan (LOS) is considered as a new generation of an effective oral drug product against arterial hypertension. Therefore, the determination of drugs in biological fluids, pharmaceuticals (tablets), and wastewater is of critical importance for clinical applications, forensics, quality control, and environmental protection that call for the development of analytical methods. Many ranges of methods such as spectroscopic methods and chromatographic techniques have been developed to determine LOS in pharmaceutical formulations and biological fluids. However, there are crucial interference problems in these methods. For these reasons, more sensitive, desirable, portable, low-cost, simple, and selective nanocomposite-based sensors are needed in terms of health safety. Nanomaterials such as reduced graphene oxide, chitosan, and metal nanoparticles are used to improve the sensitivity in the development of electrochemical sensors.

Objective:

In this study, a novel reduced graphene oxide (RGO), chitosan (Chit), gold (Au), and zinc oxide (ZnO) nanocomposite (RGO/Chitosan/Au/ZnO) was synthesized and used to develop a sensitive and efficient electrochemical sensor for LOS detection.

Methods:

Modification of electrode by RGO/Chit/Au/ZnO nanocomposite was performed in four stages with GO (at -2.0 V for 150 s), Chitosan (at -3.0 V for 300 s), Au nanoparticles (at -0.4 V for 400 s), and Zn nanoflowers like (at -0.7 V for 1200 s). The RGO/Chitosan/Au/ZnO nanocomposite was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR). Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) were used to detect LOS, and the influence of pH value, scan rate, accumulation potential, and time also losartan concentration on the performance of ZnO/Au/Chitosan/RGO/GCE were investigated. In order to investigate the selectivity of the modified electrode for the determination of LOS, the effect of possible interfering species was evaluated and showed that these species are not interferences. Also, the reproducibility of the modified electrode was investigated and implying that the RGO/Chit/Au/ZnO nanocomposite was highly reproducible.

Results:

The modified electrode was used as a sensor for the selective and sensitive determination of LOS with a detection limit of 0.073 μM over the dynamic linear range of 0.5μM to 18.0 μM. In addition, electrochemical oxidation of LOS was well recovered in pharmaceutical formulations.

Conclusion:

LOS is used to treat high blood pressure, taking into account the oxidation of this compound, the use of electrochemical based sensors, ideally suited to a specific chemical species, can be fully selectable and High-sensitivity answer is very important. In this study, the electrodes with RGO/Chit/Au/ZnO nanocomposite were modified by the electrochemical method. Nanocomposites were characterized by various methods such as FE-SEM, FT-IR, XRD, Raman, and XPS. The electrocatalytic activity of the modified electrode was then investigated for measuring LOS. According to the results of the modified electrode, high sensitivity, reproducibility, and selectivity have been shown to oxidize this composition.

An all-solid-state NO3- ion-selective electrode with gold nanoparticles solid contact layer and molecularly imprinted polymer membrane

To improve the single-layer all-solid-state ion selective electrode' defects including poor conductivity of PVC sensitive membrane and interference of water layer between substrate electrode and sensitive membrane, a double-layer all-solid-state ion selective electrode with nanomaterial as the solid contact layer and conductive polymer as the ion sensitive membrane was developed. A gold nanoparticles solid contact layer and a nitrate-doped polypyrrole molecularly imprinted polymer membrane were prepared by electrodeposition. The optimal parameters obtained by electrochemical performance test were 2.5 mmol/L HAuCl4 electrolyte for solid contact layer and 1800s electrodeposition time for sensitive membrane. The new electrode exhibited a Nernstian response of -50.4 mV/decade and a low detection limit of 5.25×10-5mol/L. Potentiometric water layer test showed no water film formed between the gold nanoparticles solid contact layer and nitrate-doped polypyrrole molecularly imprinted polymer membrane. The contact angle between droplet and the surface of solid contact layer was 112.35° and showed good hydrophobic property. Furthermore, the developed electrode exhibited fast response, excellent potential stability and long lifetime. This electrode is suitable for the detection of nitrate concentration in water and liquid fertilizer.

Advances in human chorionic gonadotropin detection technologies: a review

Human chorionic gonadotropin (HCG) is a glycoprotein secreted by placental trophoblast cells in pregnancy. HCG is a heterodimer composed of two different α- and β-subunits, with the latter being unique to HCG. As well as being the most important diagnostic markers for pregnancy, HCG is also a tumor marker, therefore, quantitative detection of HCG is of great value. Numerous advanced technologies have been developed for HCG concentration detection including electrochemical immunoassay, chemiluminescent immunoassay, fluorescence immunoassay, resonance scattering spectrometry, atomic emission spectrometry, radioimmunoassay, MS and so on. Some have pursued simple and easy operation, while others have emphasized on accuracy and applications in clinical medicine. This review provides a comprehensive summary of various methods of detecting HCG.

Biosensor Regeneration: A Review of Common Techniques and Outcomes

Biosensors are ideally portable, low-cost tools for the rapid detection of pathogens, proteins, and other analytes. The global biosensor market is currently worth over 10 billion dollars annually and is a burgeoning field of interdisciplinary research that is hailed as a potential revolution in consumer, healthcare, and industrial testing. A key barrier to the widespread adoption of biosensors, however, is their cost. Although many systems have been validated in the laboratory setting and biosensors for a range of analytes are proven at the concept level, many have yet to make a strong commercial case for their acceptance. Though it is true with the development of cheaper electrodes, circuits, and components that there is a downward pressure on costs, there is also an emerging trend toward the development of multianalyte biosensors that is pushing in the other direction. One way to reduce the cost that is suitable for certain systems is to enable their reuse, thus reducing the cost per test. Regenerating biosensors is a technique that can often be used in conjunction with existing systems in order to reduce costs and accelerate the commercialization process. This article discusses the merits and drawbacks of regeneration schemes that have been proven in various biosensor systems and indicates parameters for successful regeneration based on a systematic review of the literature. It also outlines some of the difficulties encountered when considering the role of regeneration at the point of use. A brief meta-analysis has been included in this review to develop a working definition for biosensor regeneration, and using this analysis only ∼60% of the reported studies analyzed were deemed a success. This highlights the variation within the field and the need to normalize regeneration as a standard process across the field by establishing a consensus term.

Affinity-based biosensors in sport medicine and doping control analysis

Affinity-based biosensors (ABBs) have started to be considered in sport medicine and doping control analysis because they are cheap, easy to use and sufficiently selective analytical devices, characterized by a reversible interaction with the analyte under investigation allowing the use of the same sensor for multiple analyses. In this review we describe the main categories of substances reported in the World Anti-Doping Agency Prohibited List and how ABBs may contribute to their detection. Although several ABBs proposed in the last few years display limit of detections that are in principle matching the World Anti-Doping Agency requirements, their application in the framework of 'traditional' antidoping tests seems quite unlikely, mainly because of the still insufficient selectivity especially in the case of 'pseudo-endogenous' compounds, and on the lack of complete information regarding potential matrix effects in real samples and following their routine use. At the same time, ABBs could contribute to fill a significant information gap concerning complementary evidence that can be obtained from their use 'on the spot', as well as to preselect a risk population of individuals to be targeted for a full antidoping test; while in sport medicine they could contribute to obtaining analytical information of physiological relevance from the measurement of specific parameters or markers before, during and after physical exercise.

Ultrasensitive IL-6 electrochemical immunosensor based on Au nanoparticles-graphene-silica biointerface

An Interleukin-6 (IL-6) electrochemical immunosensor was fabricated based on the Au nanoparticles (AuNP)-graphene-silica sol-gel as immobilization biointerface and AuNP-polydopamine (PDA)@carbon nanotubes (CNT) as the label of HRP-bound antibodies. The AuNP-graphene-silica sol-gel film was prepared in situ and modified on the ITO electrode, providing a stable network for the immobilization of antibody and exhibiting a dynamic working range of 1-40 pg/mL with a low detection limit of 0.3 pg/mL IL-6 (at 3s). The results of serum samples with the sensor received an acceptable agreement with the ELISA method. Importantly, this method provided a promising ultrasensitive assay strategy for clinical applications.

An amperometric immunosensor based on multi-walled carbon nanotubes-thionine-chitosan nanocomposite film for chlorpyrifos detection

In this work, a novel amperometric immunosensor based on multi-walled carbon nanotubes-thionine-chitosan (MWCNTs-THI-CHIT) nanocomposite film as electrode modified material was developed for the detection of chlorpyrifos residues. The nanocomposite film was dropped onto a glassy carbon electrode (GCE), and then the anti-chlorpyrifos monoclonal antibody was covalently immobilized onto the surface of MWCNTs-THI-CHIT/GCE using the crosslinking agent glutaraldehyde (GA). The modification procedure was characterized by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimized conditions, a linear relationship between the relative change in peak current of different pulse voltammetry (DPV) and the logarithm of chlorpyrifos solution concentration was obtained in the range from 0.1 to 1.0 × 10⁵ ng/mL with a detection limit of 0.046 ng/mL. The proposed chlorpyrifos immunosensor exhibited high reproducibility, stability, and good selectivity and regeneration, making it a potential alternative tool for ultrasensitive detection of chlorpyrifos residues in vegetables and fruits.

A sandwich HIV p24 amperometric immunosensor based on a direct gold electroplating-modified electrode

Acquired immune deficiency syndrome (AIDS) is a severe communicable immune deficiency disease caused by the human immune deficiency virus (HIV). The analysis laboratory diagnosis of HIV infection is a crucial aspect of controlling AIDS. The p24 antigen, the HIV-1 capsid protein, is of considerable diagnostic interest because it is detectable several days earlier than host-generated HIV antibodies following HIV exposure. We present herein a new sandwich HIV p24 immunosensor based on directly electroplating an electrode surface with gold nanoparticles using chronoamperometry, which greatly increased the conductivity and reversibility of the electrode. Under optimum conditions, the electrochemical signal showed a linear relationship with the concentration of p24, ranging from 0.01 ng/mL to 100 ng/mL (R > 0.99), and the detection limit was 0.008 ng/mL. Compared with ELISA, this method increased the sensitivity by more than two orders of magnitude (the sensitivity of ELISA for p24 is about 1 ng/mL). This immunosensor may be broadly applied to clinical samples, being distinguished by its ease of use, mild reaction conditions, guaranteed reproducibility, and good anti-interference ability.

Ultrasensitive electrochemical immunosensor based on Au nanoparticles dotted carbon nanotube-graphene composite and functionalized mesoporous materials

A facile and sensitive electrochemical immunosensor for detection of human chorionic gonadotrophin (hCG) was designed by using functionalized mesoporous nanoparticles as bionanolabels. To construct high-performance electrochemical immunosensor, Au nanoparticles (AuNPs) dotted carbon nanotubes (MWCNTs)-graphene composite was immobilized on the working electrode, which can increase the surface area to capture a large amount of primary antibodies (Ab(1)) as well as improve the electronic transmission rate. The as-prepared bionanolabels. composed of mesoporous silica nanoparticles (MCM-41) coated with AuNPs through thionine linking, showed good adsorption of horseradish peroxidase-labeled secondary anti-hCG antibody. Interlayer thionine was not only a bridging agent between MCM-41 and AuNPs but also an excellent electron mediator. The approach provided a good linear response range from 0.005 to 500 mIU mL(-1) with a low detection limit of 0.0026 mIU mL(-1). The immunosensor showed good precision, acceptable stability and reproducibility. Satisfactory results were obtained for determination of hCG in human serum samples. The proposed method provides a new promising platform of clinical immunoassay for other biomolecules.

Label-free electrochemical cocaine aptasensor based on a target-inducing aptamer switching conformation

A novel label-free electrochemical nucleic acid aptasensor for the determination of cocaine by the immobilization of thiolated self-assembled DNA sequences on a gold nanoparticles-modified electrode is presented. When cocaine was complexed specifically to the aptamer, the configuration of the nucleic acid aptamer switched to a locked structure and the interface of the biosensor changed, resulting in a variation of the corresponding peak current of an electrochemical probe ([Fe(CN)(6)](3-/4-)). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize modifications of the electrode surface. The peak current was detected by differential pulse voltammetry (DPV). Under the optimized experimental conditions, the presented sensor exhibits a nice specificity towards cocaine. The decrease of the peak current response of the aptasensor has a linear relationship with the concentration of cocaine ranging from 1.0 × 10(-6) to 1.5 × 10(-4) mol L(-1) with a detection limit of 3 × 10(-7) mol L(-1) at 3σ. The proposed aptasensor can be easily regenerated by the denaturalization of aptamer-target complexes in a heated water bath at 80-90°C. Besides, this biosensor has a high reproducibility and selectivity, which can be a promising method to detect cocaine in real samples.