A Dopamine Detection Sensor Based on Au-Decorated NiS2 and Its Medical Application

This article reports a simple hydrothermal method for synthesizing nickel disulfide (NiS2) on the surface of fluorine-doped tin oxide (FTO) glass, followed by the deposition of 5 nm Au nanoparticles on the electrode surface by physical vapor deposition. This process ensures the uniform distribution of Au nanoparticles on the NiS2 surface to enhance its conductivity. Finally, an Au@NiS2-FTO electrochemical biosensor is obtained for the detection of dopamine (DA). The composite material is characterized using transmission electron microscopy (TEM), UV-Vis spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The electrochemical properties of the sensor are investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and time current curves in a 0.1 M PBS solution (pH = 7.3). In the detection of DA, Au@NiS2-FTO exhibits a wide linear detection range (0.1~1000 μM), low detection limit (1 nM), and fast response time (0.1 s). After the addition of interfering substances, such as glucose, L-ascorbic acid, uric acid, CaCl2, NaCl, and KCl, the electrode potential remains relatively unchanged, demonstrating its strong anti-interference capability. It also demonstrates strong sensitivity and reproducibility. The obtained Au@NiS2-FTO provides a simple and easy-to-operate example for constructing nanometer catalysts with enzyme-like properties. These results provide a promising method utilizing Au coating to enhance the conductivity of transition metal sulfides.

Towards the design of mechanical flexible electrodes for sensing: Self-standing polypyrrole-copper nanocomposites

Self-standing electrodes with intrinsic conductivity and high electrocatalytic activity emerge as an alternative to existing sensors given their promising flexibility and wearability. Herein we demonstrate the fabrication of flexible sensors based on a hybrid nanocomposite of self-supported polypyrrole electrodes modified with copper nanoparticles (PPy-Cu) for the electrochemical detection of dopamine. The surface morphology and composition of flexible nanocomposite electrodes was studied using scanning electron microscopy (SEM), in combination with elemental mapping through energy dispersive X-ray spectroscopy (EDS). Surface characterization by X-ray photoelectron spectroscopy (XPS) revealed that copper exists in both Cu(0) and Cu(II) forms. The incorporation of copper nanoparticles in the self-standing polypyrrole matrix introduced additional electroactive sites, further enhancing charge transfer, and improving the device's sensitivity. The sensing capability of self-standing PPy-Cu electrodes was evaluated using chronoamperometric measurements and optimized at various copper electrodeposition times. PPy-Cu 120s showed great performance for dopamine sensing with a low limit of detection of 1.19 μM and a linear range of 2.5 μM-250 μM. Additionally, the self-standing sensor is comprised entirely of Polypyrrole, a biocompatible polymer, and Copper nanoparticles, making it sustainable and environmentally friendly. These encouraging results pave the way for the development of next-generation flexible sensors for the detection of neurotransmitters and environmentally relevant analytes.

Monitoring the neurotransmitter release of human midbrain organoids using a redox cycling microsensor as a novel tool for personalized Parkinson's disease modelling and drug screening

In this study, we have aimed at developing a novel electrochemical sensing approach capable of detecting dopamine, the main biomarker in Parkinson's disease, within the highly complex cell culture matrix of human midbrain organoids in a non-invasive and label-free manner. With its ability to generate organotypic structures in vitro, induced pluripotent stem cell technology has provided the basis for the development of advanced patient-derived disease models. These include models of the human midbrain, the affected region in the neurodegenerative disorder Parkinson's disease. Up to now, however, the analysis of so-called human midbrain organoids has relied on time-consuming and invasive strategies, incapable of monitoring organoid development. Using a redox-cycling approach in combination with a 3-mercaptopropionic acid self-assembled monolayer modification enabled the increase of sensor selectivity and sensitivity towards dopamine, while simultaneously reducing matrix-mediated interferences. In this work, we demonstrate the ability to detect and monitor even small differences in dopamine release between healthy and Parkinson`s disease-specific midbrain organoids over prolonged cultivation periods, which was additionally verified using liquid chromatography-multiple reaction monitoring mass spectrometry. Furthermore, the detection of a phenotypic rescue in midbrain organoids carrying a pathogenic mutation in leucine-rich repeat kinase 2, upon treatment with the leucine-rich repeat kinase 2 inhibitor II underlines the practical implementability of our sensing approach for drug screening applications as well as personalized disease modelling.

Interface-assisted synthesis: a gateway to effective nanostructure tuning of conducting polymers

The interface-assisted polymerization technique can be viewed as a powerful emerging tool for the synthesis of conducting polymers (CPs) on a large scale. Contrary to other bulk or single-phase polymerization techniques, interface-assisted synthesis strategies offer effective nanostructure control in a confined two-dimensional (2-D) space. This review focuses on the types of interfaces, mechanism at the interface, advantages and future perspectives of the interfacial polymerization in comparison to conventional polymerization techniques. Hence, the primary focus is on briefing the different types of the chemical methods of polymerization, followed by uniqueness in the reaction dynamics of interface polymerization. The classification of interfaces into four types (liquid/solid, gas/liquid, liquid/liquid, and gas/solid) is based on the versatility and underlying mechanistic pathway of the polymerization of each type. The role of interface in tuning the nanostructure of CPs and the performance evaluation of pristine CPs based on the electrical conductivity are also discussed. Finally, the future outlook of this emerging field is discussed and proposed in detail through some multifunctional applications of synthesized conducting polymers.

Recent Advances in Electrochemical and Optical Sensing of Dopamine

Nowadays, several neurological disorders and neurocrine tumours are associated with dopamine (DA) concentrations in various biological fluids. Highly accurate and ultrasensitive detection of DA levels in different biological samples in real-time can change and improve the quality of a patient's life in addition to reducing the treatment cost. Therefore, the design and development of diagnostic tool for in vivo and in vitro monitoring of DA is of considerable clinical and pharmacological importance. In recent decades, a large number of techniques have been established for DA detection, including chromatography coupled to mass spectrometry, spectroscopic approaches, and electrochemical (EC) methods. These methods are effective, but most of them still have some drawbacks such as consuming time, effort, and money. Added to that, sometimes they need complex procedures to obtain good sensitivity and suffer from low selectivity due to interference from other biological species such as uric acid (UA) and ascorbic acid (AA). Advanced materials can offer remarkable opportunities to overcome drawbacks in conventional DA sensors. This review aims to explain challenges related to DA detection using different techniques, and to summarize and highlight recent advancements in materials used and approaches applied for several sensor surface modification for the monitoring of DA. Also, it focuses on the analytical features of the EC and optical-based sensing techniques available.

Aptamers as potential recognition elements for detection of vitamins and minerals: a systematic and critical review

Background: Vitamin and mineral deficiencies are prevalent globally, and extensive efforts have been made to assess their status. Most traditional methods are expensive and time-consuming; therefore, developments of rapid, simple, specific, and sensitive methods for the assessment of vitamins and minerals in biological samples are of high importance in research. Aptamers are synthetic nucleic acid single-stranded DNA or RNA that can be synthesized in vitro. They can be engineered to be analyte-specific and have been suggested as a substitute for monoclonal antibodies, due to their high sensitivity and affinity. In addition, aptamers can be chemically synthesized and readily modified for use as biosensors. These features make aptamers a promising tool for the detection of biological analytes. In this review, we provide an overview of the potential use of aptamer-based biosensors.Methods: Search terms were conducted on several online databases, including Google Scholar, PubMed, Scopus, and Science Direct from January 2000 to August 2019. Eligibility criteria were used and quality evaluation was performed. Following the review of 4349 articles, 39 articles met the inclusion criteria.Results: Aptasensors have recently been developed for the detection of vitamins by using optical methods, with a detection range from 74 pM to 204 pM, and lower limit of detection of 2.4 pM. Both electrochemical and optical methods have been used for detection of minerals, however electrochemical methods show a wider linear range and lower detection limits compared to optical methods with a wide linear range from 0.2 fM to 1.0 mM and limit of detection of 14.7 fM.Conclusion: The current report reviews recent developments in aptamer-based biosensors for detection of vitamins and minerals. Studies have shown that aptasensors' properties are suitable for the quantification of vitamins and minerals with high sensitivity, affinity, and specificity. Nevertheless, the limitations and future directions of aptamers require further research and new technological innovation.

Early detection of cervical cancer based on high-risk HPV DNA-based genosensors: A systematic review

Human papillomavirus type (HPV) is a common cause of sexually transmitted disease (STD) in humans. HPV types 16 and 18 as the highest risk types are related with gynecologic malignancy and cervical cancer (CC) among women worldwide. Recently, considerable development of genosensors, which allows dynamic monitoring of hybridization events for HPV-16 and 18, has been a topic of focus by many researchers. In this systematic review, we highlight the route of development of DNA-based genosensory detection methods for diagnosis of high risk of HPV precancer. Biosensor detection methods of HPV-16 and 18 was investigated from 1994 to 2018 using several databases including PubMed, Cochrane Library, Scopus, Google Scholar, SID, and Scientific Information Database. Manual search of references of retrieved articles were also performed. A total of 50 studies were reviewed. By analyzing the most recent developed electrochemical biosensors for the identification of HPV, we observed that the sensor platform fabricated by Wang et al. holds the lowest detection limit reported in the literature for the DNA of HPV-16. Up to this date, optical, electrochemical, and piezoelectric systems are the main transducers used in the development of biosensors. Among the most sensitive techniques available to study the biorecognition activity of the sensors, we highlight the biosensors based fluorescent, EIS, and QCM. The current systematic review focuses on the sensory diagnostic methods that are being used to detect HPV-16 and 18 worldwide. Special emphasis is given on the sensory techniques that can diagnosis the individuals with CC. © 2018 BioFactors, 45(2):101-117, 2019.

Conducting Polymer Based Nanobiosensors

In recent years, conducting polymer (CP) nanomaterials have been used in a variety of fields, such as in energy, environmental, and biomedical applications, owing to their outstanding chemical and physical properties compared to conventional metal materials. In particular, nanobiosensors based on CP nanomaterials exhibit excellent performance sensing target molecules. The performance of CP nanobiosensors varies based on their size, shape, conductivity, and morphology, among other characteristics. Therefore, in this review, we provide an overview of the techniques commonly used to fabricate novel CP nanomaterials and their biosensor applications, including aptasensors, field-effect transistor (FET) biosensors, human sense mimicking biosensors, and immunoassays. We also discuss prospects for state-of-the-art nanobiosensors using CP nanomaterials by focusing on strategies to overcome the current limitations.

Nanocomposites of nitrogen-doped graphene decorated with a palladium silver bimetallic alloy for use as a biosensor for methotrexate detection

Pd₁Ag₁/NG–GCE is a promising platform for the highly sensitive electrochemical detection of MTX.

Self-assembly of platinum nanoparticles and coordination-driven assembly with porphyrin

The easily accessible surfaces of Pt nanostructures were demonstrated by two kinds of assembly processes.

Graphitic carbon nanocage modified electrode for highly sensitive and selective detection of dopamine

Schematic illustration of the preparation procedure of the CNCs and the electrochemical effect of the CNCs/Nafion/GCE for DA.