Utilization of an environmentally-friendly monomer for an efficient and sustainable adrenaline imprinted electrochemical sensor using graphene

Molecular imprinting technology for biomedical applications

Molecularly imprinted polymers (MIPs), a type of biomimetic material, have attracted considerable interest owing to their cost-effectiveness, good physiochemical stability, favourable specificity and selectivity for target analytes, and widely used for various biological applications. It was demonstrated that MIPs with significant selectivity towards protein-based targets could be applied in medicine, diagnostics, proteomics, environmental analysis, sensors, various in vivo and/or in vitro applications, drug delivery systems, etc. This review provides an overview of MIPs dedicated to biomedical applications and insights into perspectives on the application of MIPs in newly emerging areas of biotechnology. Many different protocols applied for the synthesis of MIPs are overviewed in this review. The templates used for molecular imprinting vary from the minor glycosylated glycan-based structures, amino acids, and proteins to whole bacteria, which are also overviewed in this review. Economic, environmental, rapid preparation, stability, and reproducibility have been highlighted as significant advantages of MIPs. Particularly, some specialized MIPs, in addition to molecular recognition properties, can have high catalytic activity, which in some cases could be compared with other bio-catalytic systems. Therefore, such MIPs belong to the class of so-called 'artificial enzymes'. The discussion provided in this manuscript furnishes a comparative analysis of different approaches developed, underlining their relative advantages and disadvantages highlighting trends and possible future directions of MIP technology.

Electrochemically Synthesized MIP Sensors: Applications in Healthcare Diagnostics

Early-stage detection and diagnosis of diseases is essential to the prompt commencement of treatment regimens, curbing the spread of the disease, and improving human health. Thus, the accurate detection of disease biomarkers through the development of robust, sensitive, and selective diagnostic tools has remained cutting-edge scientific research for decades. Due to their merits of being selective, stable, simple, and having a low preparation cost, molecularly imprinted polymers (MIPs) are increasingly becoming artificial substitutes for natural receptors in the design of state-of-the-art sensing devices. While there are different MIP preparation approaches, electrochemical synthesis presents a unique and outstanding method for chemical sensing applications, allowing the direct formation of the polymer on the transducer as well as simplicity in tuning the film properties, thus accelerating the trend in the design of commercial MIP-based sensors. This review evaluates recent achievements in the applications of electrosynthesized MIP sensors for clinical analysis of disease biomarkers, identifying major trends and highlighting interesting perspectives on the realization of commercial MIP-endowed testing devices for rapid determination of prevailing diseases.

Applications of flexible electronics related to cardiocerebral vascular system

Ensuring accessible and high-quality healthcare worldwide requires field-deployable and affordable clinical diagnostic tools with high performance. In recent years, flexible electronics with wearable and implantable capabilities have garnered significant attention from researchers, which functioned as vital clinical diagnostic-assisted tools by real-time signal transmission from interested targets in vivo. As the most crucial and complex system of human body, cardiocerebral vascular system together with heart-brain network attracts researchers inputting profuse and indefatigable efforts on proper flexible electronics design and materials selection, trying to overcome the impassable gulf between vivid organisms and rigid inorganic units. This article reviews recent breakthroughs in flexible electronics specifically applied to cardiocerebral vascular system and heart-brain network. Relevant sensor types and working principles, electronics materials selection and treatment methods are expounded. Applications of flexible electronics related to these interested organs and systems are specially highlighted. Through precedent great working studies, we conclude their merits and point out some limitations in this emerging field, thus will help to pave the way for revolutionary flexible electronics and diagnosis assisted tools development.

Picomolar or beyond Limit of Detection Using Molecularly Imprinted Polymer-Based Electrochemical Sensors: A Review

Over the last decades, molecularly imprinted polymers (MIPs) have emerged as selective synthetic receptors that have a selective binding site for specific analytes/target molecules. MIPs are synthetic analogues to the natural biological antigen-antibody system. Owing to the advantages they exhibit, such as high stability, simple synthetic procedure, and cost-effectiveness, MIPs have been widely used as receptors/sensors for the detection and monitoring of a variety of analytes. Moreover, integrating electrochemical sensors with MIPs offers a promising approach and demonstrates greater potential over traditional MIPs. In this review, we have compiled the methods and techniques for the production of MIP-based electrochemical sensors along with the applications of reported MIP sensors for a variety of analytes. A comprehensive in-depth analysis of recent trends reported on picomolar (pM/10^-12 M)) and beyond picomolar concentration LOD (≥pM) achieved using MIPs sensors is reported. Finally, we discuss the challenges faced and put forward future perspectives along with our conclusion.

Determination of 5-hydroxymethylfurfural using an electropolymerized molecularly imprinted polymer in combination with Salle

Coffee, a beverage with a complex chemical composition, is appreciated for the sensory experience of its taste and aroma. The compound 5-(hydroxymethyl)-2-furfural (HMF) is essential for sensory characterization of the beverage, and is also used in the traceability of its production. In this work, a procedure combining salting-out assisted liquid-liquid extraction (SALLE) and an electropolymerized molecularly imprinted polymer (e-MIP) was developed for the detection and quantification of HMF in coffee samples. The sample preparation step using SALLE employed a combination of acetonitrile and phosphate-buffered saline, in a proportion of 70:30 (ACN:PBS), with addition of 0.02 g of NaCl. The new sensor (e-MIP) was prepared by electropolymerization of p-aminobenzoic acid onto a glassy carbon electrode (GCE) using cyclic voltammetry (CV). Analytical determinations were performed by differential pulse voltammetry (DPV). The linear regression correlation coefficient (r²) for the response was 0.9986. The limits of detection and quantification were 0.372 mg L^-1 and 1.240 mg L^-1, respectively. The repeatability and reproducibility values obtained were 6 and 10%, respectively. The recoveries for three concentration levels were between 97 and 101%. Analyses of different coffee samples showed that the HMF concentrations varied from 261.0 ± 41.0 to 770.2 ± 55.9 mg kg^-1 in powdered coffee samples, and from 1510 ± 50 to 4445 ± 278 mg kg^-1 in instant coffee samples. The advantages of this procedure, compared to other methods described in the literature, are its simplicity, easy operation, good selectivity and sensitivity, low cost, and minimal use of organic solvents.

Development of molecularly imprinted polymer based phase boundaries for sensors design (review)

Achievements in polymer chemistry enables to design artificial phase boundaries modified by imprints of selected molecules and some larger structures. These structures seem very useful for the design of new materials suitable for affinity chromatography and sensors. In this review, we are overviewing the synthesis of molecularly imprinted polymers (MIPs) and the applicability of these MIPs in the design of affinity sensors. Such MIP-based layers or particles can be used as analyte-recognizing parts for sensors and in some cases they can replace very expensive compounds (e.g.: antibodies, receptors etc.), which are recognizing analyte. Many different polymers can be used for the formation of MIPs, but conducing polymers shows the most attractive capabilities for molecular-imprinting by various chemical compounds. Therefore, the application of conducting polymers (e.g.: polypyrrole, polyaniline, polythiophene, poly(3,4-ethylenedioxythiophene), and ortho-phenylenediamine) seems very promising. Polypyrrole is one of the most suitable for the development of MIP-based structures with molecular imprints by analytes of various molecular weights. Overoxiation of polypyrrole enables to increase the selectivity of polypyrrole-based MIPs. Methods used for the synthesis of conducting polymer based MIPs are overviewed. Some methods, which are applied for the transduction of analytical signal, are discussed, and challenges and new trends in MIP-technology are foreseen.

Biosensors Based on Bio-Functionalized Semiconducting Metal Oxides

Immobilization of biomaterials is a very important task in the development of biofuel cells and biosensors. Some semiconducting metal-oxide-based supporting materials can be used in these bioelectronics-based devices. In this article, we are reviewing some functionalization methods that are applied for the immobilization of biomaterials. The most significant attention is paid to the immobilization of biomolecules on the surface of semiconducting metal oxides. The improvement of biomaterials immobilization on metal oxides and analytical performance of biosensors by coatings based on conducting polymers, self-assembled monolayers and lipid membranes is discussed.

3D-printed electrochemical platform with multi-purpose carbon black sensing electrodes

The 3D printing is described of a complete and portable system comprising a batch injection analysis (BIA) cell and an electrochemical platform with eight sensing electrodes. Both BIA and electrochemical cells were printed within 3.4 h using a multimaterial printer equipped with insulating, flexible, and conductive filaments at cost of ca. ~ U$ 1.2 per unit, and their integration was based on a threadable assembling without commercial component requirements. Printed electrodes were exposed to electrochemical/Fenton pre-treatments to improve the sensitivity. Scanning electron microscopy and electrochemical impedance spectroscopy measurements upon printed materials revealed high-fidelity 3D features (90 to 98%) and fast heterogeneous rate constants ((1.5 ± 0.1) × 10⁻³ cm s⁻¹). Operational parameters of BIA cell were optimized using a redox probe composed of [Fe(CN)₆]^4−/3− under stirring and the best analytical performance was achieved using a dispensing rate of 9.0 µL s⁻¹ and an injection volume of 2.0 µL. The proof of concept of the printed device for bioanalytical applications was evaluated using adrenaline (ADR) as target analyte and its redox activities were carefully evaluated through different voltammetric techniques upon multiple 3D-printed electrodes. The coupling of BIA system with amperometric detection ensured fast responses with well-defined peak width related to the oxidation of ADR applying a potential of 0.4 V vs Ag. The fully 3D-printed system provided suitable analytical performance in terms of repeatability and reproducibility (RSD ≤ 6%), linear concentration range (5 to 40 µmol L⁻¹; R² = 0.99), limit of detection (0.61 µmol L⁻¹), and high analytical frequency (494 ± 13 h⁻¹). Lastly, artificial urine samples were spiked with ADR solutions at three different concentration levels and the obtained recovery values ranged from 87 to 118%, thus demonstrating potentiality for biological fluid analysis. Based on the analytical performance, the complete device fully printed through additive manufacturing technology emerges as powerful, inexpensive, and portable tool for electroanalytical applications involving biologically relevant compounds.

Electrochemically Deposited Molecularly Imprinted Polymer-Based Sensors

This review is dedicated to the development of molecularly imprinted polymers (MIPs) and the application of MIPs in sensor design. MIP-based biological recognition parts can replace receptors or antibodies, which are rather expensive. Conducting polymers show unique properties that are applicable in sensor design. Therefore, MIP-based conducting polymers, including polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene), polyaniline and ortho-phenylenediamine are frequently applied in sensor design. Some other materials that can be molecularly imprinted are also overviewed in this review. Among many imprintable materials conducting polymer, polypyrrole is one of the most suitable for molecular imprinting of various targets ranging from small organics up to rather large proteins. Some attention in this review is dedicated to overview methods applied to design MIP-based sensing structures. Some attention is dedicated to the physicochemical methods applied for the transduction of analytical signals. Expected new trends and horizons in the application of MIP-based structures are also discussed.

Carbon Nanomaterial-Based Drug Sensing Platforms Using State-of-the- Art Electroanalytical Techniques

Background:

Currently, nanotechnology and nanomaterials are considered as the most popular and outstanding research subjects in scientific fields ranging from environmental studies to drug analysis. Carbon nanomaterials such as carbon nanotubes, graphene, carbon nanofibers etc. and non-carbon nanomaterials such as quantum dots, metal nanoparticles, nanorods etc. are widely used in electrochemical drug analysis for sensor development. Main aim of drug analysis with sensors is developing fast, easy to use and sensitive methods. Electroanalytical techniques such as voltammetry, potentiometry, amperometry etc. which measure electrical parameters such as current or potential in an electrochemical cell are considered economical, highly sensitive and versatile techniques.

Methods:

Most recent researches and studies about electrochemical analysis of drugs with carbon-based nanomaterials were analyzed. Books and review articles about this topic were reviewed.

Results:

The most significant carbon-based nanomaterials and electroanalytical techniques were explained in detail. In addition to this; recent applications of electrochemical techniques with carbon nanomaterials in drug analysis was expressed comprehensively. Recent researches about electrochemical applications of carbon-based nanomaterials in drug sensing were given in a table.

Conclusion:

Nanotechnology provides opportunities to create functional materials, devices and systems using nanomaterials with advantageous features such as high surface area, improved electrode kinetics and higher catalytic activity. Electrochemistry is widely used in drug analysis for pharmaceutical and medical purposes. Carbon nanomaterials based electrochemical sensors are one of the most preferred methods for drug analysis with high sensitivity, low cost and rapid detection.

MXene/carbon nanohorns decorated with conductive molecularly imprinted poly(hydroxymethyl-3,4-ethylenedioxythiophene) for voltammetric detection of adrenaline

A novel molecularly imprinted sensor was developed for the voltammetric determination of adrenaline (AD). MXene/carbon nanohorn (MXene/CNH) composite with good electric conductivity and enormous accessible active sites was firstly introduced as catalytic substrate. Subsequently, molecularly imprinted polymer (MIP) film was fabricated in mixed solutions containing hydroxymethyl-3,4-ethylenedioxythiophene (functional monomer) and AD (template) through electro-polymerization process. A molecularly imprinted sensor was formed after removing the template. The morphology and elemental composition of the prepared composites were studied by scanning electron microscopy and X-ray photoelectron spectroscopy. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical performance of the molecularly imprinted sensors. Under optimized conditions, the designed sensor displays a wide linear range from 1.0 nM to 60.0 μM and a low limit of detection of 0.3 nM. The developed sensor also presents good selectivity, reproducibility and long-term stability, and satisfactory feasibility in practical sample analysis. MXene/carbon nanohorns decorated with conductive molecularly imprinted poly(hydroxymethyl-3,4-ethylenedioxythiophene) was proposed for highly sensitive and selective detection of adrenaline.

Nanocomposite Materials Based on Electrochemically Synthesized Graphene Polymers: Molecular Architecture Strategies for Sensor Applications

The use of graphene and its derivatives in the development of electrochemical sensors has been growing in recent decades. Part of this success is due to the excellent characteristics of such materials, such as good electrical and mechanical properties and a large specific surface area. The formation of composites and nanocomposites with these two materials leads to better sensing performance compared to pure graphene and conductive polymers. The increased large specific surface area of the nanocomposites and the synergistic effect between graphene and conducting polymers is responsible for this interesting result. The most widely used methodologies for the synthesis of these materials are still based on chemical routes. However, electrochemical routes have emerged and are gaining space, affording advantages such as low cost and the promising possibility of modulation of the structural characteristics of composites. As a result, application in sensor devices can lead to increased sensitivity and decreased analysis cost. Thus, this review presents the main aspects for the construction of nanomaterials based on graphene oxide and conducting polymers, as well as the recent efforts made to apply this methodology in the development of sensors and biosensors.

Enantioselective recognition of tryptophan isomers with molecularly imprinted overoxidized polypyrrole/poly(p-aminobenzene sulfonic acid) modified electrode

Poly(p-aminobenzene sulfonic acid) (pABSA) was electrodeposited onto the surface of a glassy carbon electrode (GCE), which was then used for the preconcentration of l-tryptophan (l-Trp) due to the electrostatic and π-π interactions between pABSA and l-Trp. Polypyrrole (PPy) was electrodeposited onto the surface of the l-Trp enriched pABSA, and then the l-Trp templates were removed, resulting in molecularly imprinted PPy/pABSA. To avoid the interference from the oxidation peak of PPy on the following electrochemical chiral recognition of Trp isomers, PPy was overoxidized by cyclic voltammetry (CV). The resultant molecularly imprinted overoxidized PPy (OPPy)/pABSA modified GCE exhibits higher affinity toward l-Trp than d-tryptophan (d-Trp); that is, the oxidation peak current of l-Trp is greatly higher than that of d-Trp at the molecularly imprinted OPPy/pABSA modified GCE.

Advances in Molecularly Imprinted Polymers Based Affinity Sensors (Review)

Recent challenges in biomedical diagnostics show that the development of rapid affinity sensors is very important issue. Therefore, in this review we are aiming to outline the most important directions of affinity sensors where polymer-based semiconducting materials are applied. Progress in formation and development of such materials is overviewed and discussed. Some applicability aspects of conducting polymers in the design of affinity sensors are presented. The main attention is focused on bioanalytical application of conducting polymers such as polypyrrole, polyaniline, polythiophene and poly(3,4-ethylenedioxythiophene) ortho-phenylenediamine. In addition, some other polymers and inorganic materials that are suitable for molecular imprinting technology are also overviewed. Polymerization techniques, which are the most suitable for the development of composite structures suitable for affinity sensors are presented. Analytical signal transduction methods applied in affinity sensors based on polymer-based semiconducting materials are discussed. In this review the most attention is focused on the development and application of molecularly imprinted polymer-based structures, which can replace antibodies, receptors, and many others expensive affinity reagents. The applicability of electrochromic polymers in affinity sensor design is envisaged. Sufficient biocompatibility of some conducting polymers enables to apply them as "stealth coatings" in the future implantable affinity-sensors. Some new perspectives and trends in analytical application of polymer-based semiconducting materials are highlighted.

Electroanalytical profiling of cocaine samples by means of an electropolymerized molecularly imprinted polymer using benzocaine as the template molecule

Cocaine samples were ‘finger-printed’ using e-MIPs, constructed on the surface of portable SPCEs. The SWV data with suitable chemometric analysis provides valuable information about the drugs’ provenience which is crucial to tackle drug traffic.

Conducting Polymers in the Design of Biosensors and Biofuel Cells

Fast and sensitive determination of biologically active compounds is very important in biomedical diagnostics, the food and beverage industry, and environmental analysis. In this review, the most promising directions in analytical application of conducting polymers (CPs) are outlined. Up to now polyaniline, polypyrrole, polythiophene, and poly(3,4-ethylenedioxythiophene) are the most frequently used CPs in the design of sensors and biosensors; therefore, in this review, main attention is paid to these conducting polymers. The most popular polymerization methods applied for the formation of conducting polymer layers are discussed. The applicability of polypyrrole-based functional layers in the design of electrochemical biosensors and biofuel cells is highlighted. Some signal transduction mechanisms in CP-based sensors and biosensors are discussed. Biocompatibility-related aspects of some conducting polymers are overviewed and some insights into the application of CP-based coatings for the design of implantable sensors and biofuel cells are addressed. New trends and perspectives in the development of sensors based on CPs and their composites with other materials are discussed.

Application of molecularly imprinted polymers in the anti-doping field: sample purification and compound analysis

The problem posed by anti-doping requirements is one of the great analytical challenges; multiple compound detection at low ng ml-1 levels from complex samples, with requirements for exceptional confidence in results. This review surveys the design, synthesis and application of molecularly imprinted polymers (MIPs) in this field, focusing on the templating of androgenous anabolic steroids (AASs), as the most commonly abused substances, but also other WADA prohibited substances. Commentary on the application of these materials in detection, clean-up and sensing is offered, alongside views on the future of imprinting in this field.

Functional Polymers Structures for (Bio)Sensing Application-A Review

In this review we present polymeric materials for (bio)sensor technology development. We focused on conductive polymers (conjugated microporous polymer, polymer gels), composites, molecularly imprinted polymers and their influence on the design and fabrication of bio(sensors), which in the future could act as lab-on-a-chip (LOC) devices. LOC instruments enable us to perform a wide range of analysis away from the stationary laboratory. Characterized polymeric species represent promising candidates in biosensor or sensor technology for LOC development, not only for manufacturing these devices, but also as a surface for biologically active materials' immobilization. The presence of biological compounds can improve the sensitivity and selectivity of analytical tools, which in the case of medical diagnostics is extremely important. The described materials are biocompatible, cost-effective, flexible and are an excellent platform for the anchoring of specific compounds.

Bacterial Imprinting Methods and Their Applications: An Overview

Microbial contaminations and infections are hazardous and pose crucial concerns for humans. They result in severe morbidity and mortality around the globe. Even though dish-culturing, polymerase chain reaction (PCR), an enzyme-linked immunosorbent assay (ELISA) exhibits accurate and reliable detection of bacteria but these methods are time-consuming, laborious, and expensive. This warrants early detection and quantification of bacteria for timely diagnosis and treatment. Bacteria imprinting ensures a solution for selective and early detection of bacteria by snagging them inside their imprinted cavities. This review provides an insight into MIPs based bacterial detection strategies, challenges, and future perspectives.

A flexible-imprinted capacitive sensor for rapid detection of adrenaline

This article demonstrates a non-enzymatic biomimetic adrenaline capacitive sensor fabricated inexpensively by layer-by-layer (LbL) assembly. The LbL assembly consists of polydimethylsiloxane (PDMS) substrate, carbon nanotube-cellulose nanocrystals (CNC/CNT) nanofilms (first layer) with adrenaline imprinted poly (aniline/phenylboronic acid) (pANI/PBA) moieties (second layer). The flexible sensor has been effectively demonstrated for high sensitivity and selectivity in capacitive detection of adrenaline standard and adrenaline in real zebra fish brain sample. The molecularly imprinted adrenaline sensor exhibited linear response between 0.001  μM and 100  μM with a correlation coefficient of 0.9738 and detection limit (LOD) of 0.001  μM. The developed sensor demonstrated high adrenaline selectivity and good sensor to sensor reproducibility of 15.7% for molecularly imprinted films. The sensor precision for triplicate standard runs for different adrenaline concentrations ranged from 0.5 to 5.0%, indicative of the overall reliability and validity of the device. The inexpensive sensor remains stable over time, responding proportionately to doses of adrenaline, and as such effective as a dosimetric sensor for near real time continuous monitoring. Frugal in sample consumption (50 μL), the study suggested the practical utilization of the developed biosensor towards adrenaline detection in biological fluids.

Facile preparation of molybdenum carbide (Mo2C) nanoparticles and its effective utilization in electrochemical sensing of folic acid via imprinting

Herein, we propose a facile chemical reduction method to synthesize the molybdenum carbide (Mo₂C) nanoparticles and its application for the electrochemical detection of folic acid (FA) through imprinting technique. Raman scattering, photoelectron spectroscopy and electron microscopy techniques were employed to study the properties of Mo₂C nanoparticles. FA imprinting was carried out in the presence of pyrrole monomer over Mo₂C modified glassy carbon electrode (GCE). The proposed sensor showed the detection behavior for wide range of FA concentrations from 0.01 μM to 120 μM with an excellent LOD value of 4 nM and good selectivity toward FA as compared to other co-existing species in real samples. The fabricated MIP-Mo₂C/GCE sensors were able to be replicated with ∼1.9% RSD, and their reproduced sensor offered good repeatability (RSD; 1.6%) and stability.

Recent Advances in Electrosynthesized Molecularly Imprinted Polymer Sensing Platforms for Bioanalyte Detection

The accurate detection of biological materials has remained at the forefront of scientific research for decades. This includes the detection of molecules, proteins, and bacteria. Biomimetic sensors look to replicate the sensitive and selective mechanisms that are found in biological systems and incorporate these properties into functional sensing platforms. Molecularly imprinted polymers (MIPs) are synthetic receptors that can form high affinity binding sites complementary to the specific analyte of interest. They utilise the shape, size, and functionality to produce sensitive and selective recognition of target analytes. One route of synthesizing MIPs is through electropolymerization, utilising predominantly constant potential methods or cyclic voltammetry. This methodology allows for the formation of a polymer directly onto the surface of a transducer. The thickness, morphology, and topography of the films can be manipulated specifically for each template. Recently, numerous reviews have been published in the production and sensing applications of MIPs; however, there are few reports on the use of electrosynthesized MIPs (eMIPs). The number of publications and citations utilising eMIPs is increasing each year, with a review produced on the topic in 2012. This review will primarily focus on advancements from 2012 in the use of eMIPs in sensing platforms for the detection of biologically relevant materials, including the development of increased polymer layer dimensions for whole bacteria detection and the use of mixed monomer compositions to increase selectivity toward analytes.

Molecular Imprinting Prevents Environmental Contamination and Body Toxicity from Anticancer Drugs: An Update

Cancer has been responsible for high morbidity and mortality globally. The treatment of cancer is possible using different kinds of therapies using anticancer drugs if it is diagnosed at the right time. Nevertheless, their appropriate administration for maximum therapeutic effect and their elimination from the patient's body causing environmental problems are two big issues which could be successfully abated using molecular imprinted polymers (MIPs) owing to their unique features. In this review, we have compiled and discussed the works on the determination and controlled release of anticancer drugs based on MIPs. We also highlighted the current challenges and remedies, and the future direction of MIPs in this area.

Effective imprinting of an anticancer drug, 6-thioguanine,viamussel-inspired self-polymerization of dopamine over reduced graphene oxide

Apart from being a vital catecholamine molecule responsible for the proper functioning of the central nervous system (CNS), hormonal and renal systems, dopamine (DA) has also been increasingly employed as a functional monomer in the fabrication of surface molecular imprinting polymers (MIPs) for valuable analytes.

Electrochemical Determination of Adrenaline Using MXene/Graphite Composite Paste Electrodes

MXene/graphite composite paste electrode (MXene/GCPE)-based electrochemical sensor has been fabricated for the detection of adrenaline. The electrode exhibits a sensitive response to adrenaline in phosphate buffer solution of pH 7.4, and its catalytic activity is much higher than that of the bare graphite paste electrode. The electron-transfer reaction of MXene/GCPE is a diffusion controlled process. The graph of concentration of adrenaline with the peak current exhibits two linearities, one in the lower and other in the higher concentration range with a detection limit of 9.5 nM. The simultaneous analyses of adrenaline, ascorbic acid, and serotonin reveal that the fabricated electrode could separate the overlapped cyclic voltammetric peaks of these ternary mixtures. This electrode has been further employed in the detection of adrenaline in pharmaceutical samples with 99.2-100.8% recoveries.

Development of molecularly imprinted electrochemical sensor with reduced graphene oxide and titanium dioxide enhanced performance for the detection of toltrazuril in chicken muscle and egg

A molecularly imprinted electrochemical sensor for toltrazuril (TZR) detection based on molecularly imprinted polymers (MIPs) immobilized on reduced graphene oxide (rGO) and titanium dioxide (TiO₂) modified platinum (Pt) electrode surface was fabricated for the first time. The synergistic fast electron transfer ability, large electroactive surface area and high catalytic activity from rGO and TiO₂ contribute to amplify the electrochemical signal and consequently improve the sensitivity of the sensor. The cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) tests were used to evaluate the performance of the electrochemical sensor. The results showed that the electrochemical sensor possessed high sensitivity, good selectivity and anti-interference ability toward TZR. By using the DPV, the electrochemical sensor displayed a wide linear concentration range from 0.43 to 42.54 μg/L, with a limit of detection of 0.21 μg/L (S/N = 3). Moreover, the recoveries and relative standard deviations (RSD) were 85.0%-97.0% and 3.5%-6.4% at three concentration levels, respectively, implying that the established sensor is promising for the accurate detection of TZR at trace levels in chicken muscle and egg samples.