Selective extraction and determination of catecholamines in urine samples by using a dopamine magnetic molecularly imprinted polymer and capillary electrophoresis

Design and green synthesis of carbon Dots/Gold nanoparticles Composites and their applications for neurotransmitters sensing based on emission Spectroscopy

Changes in the neurotransmitters are indications for several diseases. Several sensors were reported for monitoring dopamine (DA), but the simple and accurate DA detection in biological samples still faces many challenges. The research proposal aims to develop an optical sensor for detecting neurotransmitters based on luminescence emission spectra in different biological samples. Carbon dots (CDs) were fabricated based on a green synthesis route. Then the prepared CDs were decorated with varying concentrations of gold nanoparticles (Au NPs). The synthesis process was optimized, and the obtained CDs/Au NPs nanocomposites were applied as neurotransmitters' optical nanosensors. The optical nanosensor approach provides easy and sensitive multiplex analysis. A wide range of neurotransmitters was monitored. The developed sensor's sensitivity, selectivity, and reproducibility were investigated. Au NPs act as CDs' stabilizers, enhancing the emission effect, and scaffolds for binding DA with CDs' surface. DA moieties bind to CDs through the interaction between the DA-NH2 groups and Au NPS. Due to electron transfer, the bonding of DA molecules leads to fluorescence quenching of AuNPs/CDs. The Au-CDs-based DA fluorescence showed high sensitivity with adetection limit, and limit quantification of 2.04 nM and 6.18 nM, respectively. Furthermore, the selectivity of the sensor was investigated in the presence of glucose, uric acid (UA), and ascorbic acid (AA), which showed no interference effect at 10 times higher concentrations. Moreover, the proposed sensor has been successfully utilized for DA detection in human serum samples with a high recovery efficiency between 98.83 % and 103.5 %.

Enhanced detection of catecholamines in human urine using Cis-diol-microporous organic networks with PT-SPE and HPLC-MS/MS

A novel cis-diol-microporous organic networks (MONs-2OH) material was synthesized via room temperature and Sonogashira coupling reactions, which exhibits exceptional adsorption properties for catecholamines (CAs). MONs-2OH demonstrates robust hydrogen bonding and π-π stacking interactions, crucial for effective adsorption. The MONs-2OH was incorporated into pipette tip solid-phase extraction and developed a new method for detecting CAs in human urine using HPLC-MS/MS. Characterization of the adsorbent revealed its high stability, large specific surface area, abundant phenolic hydroxyl groups, rapid extraction speed, and superior adsorption efficiency. The method achieved a wide linear range (0.5-500 ng/mL), low detection limits (0.06-0.26 ng/mL), high accuracy (90.4 %-99.4 %), and excellent precision (RSD ≤ 10 %). Comparative studies showed MONs-2OH outperforms commercial adsorbents in terms of recovery and adsorption capacity. The results underscore the potential of MONs-2OH for rapid and sensitive CAs determination, offering significant advantages for the auxiliary diagnosis of depression and enhancing the application of PT-SPE in sample pretreatment.

Molecularly Imprinted Polypyrrole-Modified Screen-Printed Electrode for Dopamine Determination

This paper introduces a quantitative method for dopamine determination. The method is based on a molecularly imprinted polypyrrole (e-MIP)-modified screen-printed electrode, with differential pulse voltammetry (DPV) as the chosen measurement technique. The dopamine molecules are efficiently entrapped in the polymeric film, creating recognition cavities. A comparison with bare and non-imprinted polypyrrole-modified electrodes clearly demonstrates the superior sensitivity, selectivity, and reproducibility of the e-MIP-based one; indeed, a sensitivity of 0.078 µA µM-1, a detection limit (LOD) of 0.8 µM, a linear range between 0.8 and 45 µM and a dynamic range of up to 350 µM are achieved. The method was successfully tested on fortified synthetic and human urine samples to underline its applicability as a screening method for biomedical tests.

The influence of bismuth participation on the morphological and electrochemical characteristics of gallium oxide for the detection of adrenaline

In this work, we investigated the morphological and electrochemical properties of gallium/bismuth mixed oxide. The bismuth concentration was varied from 0 to 100%. The correct ratio was determined with inductively coupled plasma-optical emission spectroscopy (ICP-OES), while surface characteristics were determined using scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurement. Electrochemical characteristics were studied using electrochemical impedance spectroscopy (EIS) in the Fe^2+/3+ couple. The obtained materials were tested for adrenaline detection. After square wave voltammetry (SWV) optimization, the best electrode showed a wide linear working range from 7 to 100 µM at pH 6 of the Britton-Robinson buffer solution (BRBS) supporting electrolyte. The limit of detection (LOD) for the proposed method was calculated as 1.9 µM, with a limit of quantification (LOQ) of 5.8 µM. The excellent selectivity of the proposed method, with good repeatability and reproducibility, strongly suggests the possible application of the procedure for the determination of adrenaline in artificially prepared real samples. The practical applicability with good recovery values indicates that the morphology of the materials is closely connected with other parameters, which further suggests that the developed approach can offer a low-cost, rapid, selective, and sensitive method for adrenaline monitoring.

Polyindole-Derived Nitrogen-Doped Graphene Quantum Dots-Based Electrochemical Sensor for Dopamine Detection

The sensitive monitoring of dopamine levels in the human body is of utmost importance since its abnormal levels can cause a variety of medical and behavioral problems. In this regard, we report the synthesis of nitrogen-doped graphene quantum dots (N-GQDs) from polyindole (PIN) via a facile single-step hydrothermal synthetic strategy that can act as an efficient electrochemical catalyst for the detection of dopamine (DA). The average diameter of N-GQDs was ∼5.2 nm and showed a C/N atomic ratio of ∼2.75%. These N-GQDs exhibit a cyan fluorescence color under irradiation from a 365 nm lamp, while PIN has no characteristic PL. The presence of richly N-doped graphitic lattices in the N-GQDs possibly accounts for the improved catalytic activity of N-GQDs/GCE towards electrocatalytic DA detection. Under optimum conditions, this novel N-GQDs-modified electrode exhibits superior selectivity and sensitivity. Moreover, it could detect as low as 0.15 nM of DA with a linear range of 0.001-1000 µM. In addition, the outstanding sensing attributes of the detector were extended to the real samples as well. Overall, our findings evidence that N-GQDs-based DA electrochemical sensors can be synthesized from PIN precursor and could act as promising EC sensors in medical diagnostic applications.

Dual-Template Magnetic Molecularly Imprinted Polymer for Simultaneous Determination of Spot Urine Metanephrines and 3-Methoxytyramine for the Diagnosis of Pheochromocytomas and Paragangliomas

A novel dual-template magnetic molecularly imprinted polymer (MMIP) was synthesized to extract normetanephrine (NMN), metanephrine (MN) and 3-methoxytyramine (3-MT) from spot urine samples. As the adsorbent of dispersive solid-phase extraction (d-SPE), the MMIP was prepared using dopamine and MN as dual templates, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the crosslinking reagent and magnetic nanoparticles as the magnetic core. NMN, MN, 3-MT and creatinine (Cr) in spot urine samples were selectively enriched by d-SPE and detected by HPLC-fluorescence detection/ultraviolet detection. The peak area (A) ratios of NMN, MN and 3-MT to Cr were used for the diagnosis of pheochromocytomas and paragangliomas (PPGLs). The results showed that the adsorption efficiencies of MMIP for target analytes were all higher than 89.0%, and the coefficient variation precisions of intra-assay and inter-assay for the analytes were within 4.9% and 6.3%, respectively. The recoveries of the analytes were from 93.2% to 112.8%. The MMIP was still functional within 14 days and could be reused at least seven times. The d-SPE and recommended solid-phase extraction (SPE) were both used to pretreat spot urine samples from 18 PPGLs patients and 22 healthy controls. The correlation coefficients of A_NMN/A_Cr and A_MN/A_Cr between d-SPE and SPE were both higher than 0.95. In addition, the areas under the receiver operator curves for spot urine A_NMN/A_Cr, A_MN/A_Cr and plasma free NMN and MN were 0.975, 0.773 and 0.990, 0.821, respectively, indicating the two methods had the similar performances. The d-SPE method took only 20 min, which was effective in clinical application.

Efficient synthesis of boronate affinity-based catecholamine-imprinted magnetic nanomaterials for trace analysis of catecholamine in human urine

Catecholamines, a class of cis-diol-containing compounds, play a major role in the central nervous system.

Efficient Sub-1 Minute Analysis of Selected Biomarker Catecholamines by Core-Shell Hydrophilic Interaction Liquid Chromatography (HILIC) with Nanomolar Detection at a Boron-Doped Diamond (BDD) Electrode

A rapid, sensitive method for the separation of catecholamine biomarkers (CAs), of importance in traumatic brain injury (TBI) and in Parkinson’s disease (PD), has been successfully developed using hydrophilic interaction liquid chromatography (HILIC). Dopamine (DA), epinephrine (EPI), and norepinephrine (NE) are known to be three to fivefold elevated above normal in traumatic brain injury (TBI) patients. HILIC facilitates the rapid and efficient separation of these polar biomarkers, which can be poorly retained by reversed-phase liquid chromatography (RPLC), while electrochemical detection (ECD) at the boron-doped diamond (BDD) electrode provides enhanced nanomolar detection. Three HILIC columns were compared, namely the superficially porous (core-shell) Z-HILIC column and the Z-cHILIC and Z-HILIC fully porous columns. The core-shell Z-HILIC showed the highest efficiency with a rapid separation within 60 s. The HILIC method utilizing the core-shell Z-HILIC column was initially optimized for the simultaneous analysis of DA, EPI, and NE using UV detection. The advantages of using the BDD electrode over UV detection were explored, and the improved limits of detection (LODs, S/N = 3) measured were 40, 50, and 50 nM for DA, EPI, and NE, respectively. Method validation is reported in terms of the linearity, repeatability, reproducibility, and LODs. Furthermore, the proposed method was successfully applied to the real sample analysis of urinary CAs following phenylboronic acid (PBA) solid phase extraction (SPE) pretreatment.

Surface Polymers on Multiwalled Carbon Nanotubes for Selective Extraction and Electrochemical Determination of Rhodamine B in Food Samples

In this study, we combine magnetic solid phase extraction (MSPE), with the screen-printed carbon electrode (SPCE) modified by a molecular imprinted polymer (MIP) for sensitive and selective extraction and electrochemical determination of Rhodamine B in food samples. A magnetic solid phase extraction (MSPE) was carried out using magnetic poly(styrene-co-divinylbenzene) (PS-DVB) and magnetic nanoparticles (MNPs) synthetized on the surface of multiwalled carbon nanotubes (MWCNTs). An MIP was prepared on the surface of MWCNTs in the presence of titanium oxide nanoparticles (TiO₂NPs) modifying the SPCE for the rapid electrochemical detection of Rhodamine B. The MIPs synthesis was optimized by varying the activated titanium oxide (TiO₂) and multiwalled carbon nanotubes (MWCNTs) amounts. The MSPE and electrochemical detection conditions were optimized as well. The present method exhibited good selectivity, high sensitivity, and good reproducibility towards the determination of Rhodamine B, making it a suitable method for the determination of Rhodamine B in food samples.

Application of magnetic nanomaterials in bioanalysis

The importance of magnetic nanomaterials and magnetic hybrid materials, which are classified as new generation materials, in analytical applications is increasingly understood, and research on the adaptation of these materials to analytical methods has gained momentum. Development of sample preparation techniques and sensor systems using magnetic nanomaterials for the analysis of inorganic, organic and biomolecules in biological samples, which are among the samples that analytical chemists work on most, are among the priority issues. Therefore in this review, we focused on the use of magnetic nanomaterials for the bioanalytical applications including inorganic and organic species and biomolecules in different biological samples such as primarily blood, serum, plasma, tissue extracts, urine and milk. We summarized recent progresses, prevailing techniques, applied formats, and future trends in sample preparation-analysis methods and sensors based on magnetic nanomaterials (Mag-NMs). First, we provided a brief introduction of magnetic nanomaterials, especially their magnetic properties that can be utilized for bioanalytical applications. Second, we discussed the synthesis of these Mag-NMs. Third, we reviewed recent advances in bioanalytical applications of the Mag-NMs in different formats. Finally, recently literature studies on the relevance of Mag-NMs for bioanalysis applications were presented.

A new nanometrological strategy for titanium dioxide nanoparticles screening and confirmation in personal care products by CE-spICP-MS

A new nanometrological approach was developed for screening of titania nanoparticles by capillary electrophoresis after adsorption of a target analyte namely l-cysteine onto the nanoparticles in a sodium phosphate buffer, followed by titanium elemental analysis by means of inductively-coupled plasma-mass spectrometry and size distribution measurements by single-particle mode. This analytical strategy involved a first screening of nanotitania in actual samples by electrophoresis, sensitivity being enhanced by cysteine which acts as a nanoparticles stabiliser. Detection and quantitation limits were 0.31 ng μL^-1 and 1.03 ng μL^-1 respectively for anatase nanoparticles in capillary electrophoresis, and a high amount of titanium was found in the samples subject to study (lip balm and two types of toothpaste) by total elemental analysis. Besides, the potential of single-particle modality for inductively-coupled plasma-mass spectrometry was exploited for a verification of particle size distribution, then confirming the presence of titanium dioxide nanoparticles as an ingredient in the composition of the real samples and validating the overall strategy herein presented.

LC-MS determination of catecholamines and related metabolites in red deer urine and hair extracted using magnetic multi-walled carbon nanotube poly(styrene-co-divinylbenzene) composite

A novel analytical methodology for the extraction and determination of catecholamines (dopamine, epinephrine and norepinephrine) and their metabolites DL-3,4-dihydroxyphenyl glycol and DL-3,4-dihydroxymandelic acid by LC-MS is developed and validated for its application to human and animal urine and hair samples. The method is based on the preliminary extraction of the analytes by a magnetic multi-walled carbon nanotube poly(styrene-co-divinylbenzene) composite. This is followed by a <9 min chromatographic separation of the target compounds in an Onyx Monolithic C₁₈ column using a mixture of 0.01% (v/v) heptafluorobutyric acid in water and methanol at 500 µL min^-1 flow rate. Detection limits within range from 0.055 to 0.093 µg mL^-1, and precision values of the response and retention times of analytes were >90%. Accuracy values comprised the range 79.5-109.5% when the analytes were extracted from deer urine samples using the selected MMWCNT-poly(STY-DVB) sorbent. This methodology was applied to real red deer urine and hair samples, and concentrations within range from 0.05 to 0.5 µg mL^-1 for norepinephrine and from 1.0 to 44.5 µg mL^-1 for its metabolite 3,4-dihydroxyphenyl glycol were calculated. Analyses of red deer hair resulted in high amounts of 3,4-dihydroxyphenyl glycol (0.9-266.9 µg mL^-1).

Magnetic molecularly imprinted polymer prepared by microwave heating for confirmatory determination of chloramphenicol in chicken feed using high-performance liquid chromatography-tandem mass spectrometry

A magnetic molecularly imprinted polymer (MMIP) for chloramphenicol was prepared using a surface-imprinted and microwave-heating-induced polymerization method. The surfaces of the magnetic particles were first double-bond functionalized with 3-(trimethoxysilyl)propyl methacrylate (γ-MPS), followed by the copolymerization of 4-vinyl pyridine (4-VP) and trimethylolpropane trimethacrylate (TRIM) in the presence of chloramphenicol as a template and 1,1-azobis(cyclohexane-carbonitrile) (ABCN) as an initiator in a mixture of dimethyl sulfoxide and water with microwave heating at 80°C. The magnetic polymer possesses supraparamagnetic properties and was used to concentrate and cleanup chicken feed extract, followed by chromatographic separation using a Lichrospher®100 RP C8 column and detection with two multi-reaction monitoring transitions at m/z 321→ 152 and m/z 321→ 257. The mean recoveries obtained at two spiking levels were in the range of 94.6-100% The relative intra- and inter-day standard deviations were in the range of 1.4-2.6% and 5.1-5.7%, respectively. The detection limit of the method was 0.12 µg kg^-1. This confirmatory method was successfully applied to determine chloramphenicol in chicken feed samples.

Nanostructured carbon electrode modified with N-doped graphene quantum dots-chitosan nanocomposite: a sensitive electrochemical dopamine sensor

A highly selective and sensitive dopamine electrochemical sensor based on nitrogen-doped graphene quantum dots-chitosan nanocomposite-modified nanostructured screen printed carbon electrode is presented, for the first time. Graphene quantum dots were prepared via microwave-assisted hydrothermal reaction of glucose, and nitrogen doping was realized by introducing ammonia in the reaction mixture. Chitosan incorporation played a significant role towards the selectivity of the prepared sensor by hindering the ascorbic acid interference and enlarging the peak potential separation between dopamine and uric acid. The proposed sensor's performance was shown to be superior to several recently reported investigations. The as-prepared CS/N,GQDs@SPCE exhibited a high sensitivity (i.e. ca. 418 µA mM cm^-2), a wide linear range i.e. (1-100 µM) and (100-200 µM) with excellent correlations (i.e. R² = 0.999 and R² = 1.000, respectively) and very low limit of detection (LOD = 0.145 µM) and limit of quantification (LOQ = 0.482 µM) based on S/N = 3 and 10, respectively. The applicability of the prepared sensor for real sample analysis was tested by the determination of dopamine in human urine in pH 7.0 PBS showing an approximately 100% recovery with RSD < 2% inferring both the practicability and reliability of CS/N,GQDs@SPCE. The proposed sensor is endowed with high reproducibility (i.e. RSD = ca. 3.61%), excellent repeatability (i.e. ca. 0.91% current change) and a long-term stability (i.e. ca. 94.5% retained activity).

Assessment of the binding performance of histamine-imprinted microspheres by frontal analysis capillary electrophoresis

Frontal analysis capillary electrophoresis was used to evaluate the binding performance of molecularly imprinted microspheres (MIM) toward its template histamine and analogs at pH 7, and compared to the high performance liquid chromatographic method. In both methods, batch binding was employed and the binding parameters were calculated from the measured concentration of unbound amine analytes and afforded comparable histamine equilibrium dissociation constants (K_d ∼ 0.4 mM). FACE was easily carried out at shorter binding equilibration time (i.e. 30 min) and without the need to separate the microspheres, circumventing laborious and, in the case of the system under study, inefficient sample filtration. It also allowed for competitive binding studies by virtue of its ability to distinctly separate intact microspheres and all tested amines which could not be resolved in HPLC. K_d 's for nonimprinted (control) microspheres (NIM) from FACE and HPLC were also comparable (∼ 0.6 mM) but at higher histamine concentrations, HPLC gave lower histamine binding. This discrepancy was attributed to inefficient filtration of the batch binding samples prior to HPLC analysis resulting in an over-estimation of the concentration of free histamine brought about by the presence of unfiltered histamine-bound microspheres.

Recent configurations and progressive uses of magnetic molecularly imprinted polymers for drug analysis

Since the introduction of the molecularly imprinting technology (MIT) in the 1970s, it becomes an emerging technology with the potential for wide-ranging applications in drug determination. With the rise of green chemistry, many researchers began to focus on the application and development of green materials which led to the breakthrough of molecularly imprinted polymers (MIPs) in the green chemistry. Because of the low concentration levels in the human matrices, almost adequate analytical methods should be used for quantification of drugs at the trace levels. In recent years there have been reported benefits of combining MIPs with additional features, e.g. magnetic properties, through the build-up of this type of material on magnetite particles. Magnetic molecularly imprinted polymer (MMIP) is a new material which is composed of magnetic material and non-magnetic polymer material and shares the characteristics of high adsorption capacity to template molecule, special selective recognition ability, and the magnetic adsorption property. These materials have been widely used in the different fields such as chemical, biological and medical science. This review describes the novel configurations and progressive applications of magnetic molecularly imprinted polymers to the drug analysis. Also, the advantages and drawbacks of each methodology, as well as the future expected trends, are evaluated.

Determination of monoamine neurotransmitters in zebrafish (Danio rerio) by gas chromatography coupled to mass spectrometry with a two-step derivatization

A sensitive analytical method for the determination of monoamine neurotransmitters (MNTs) in zebrafish larvae was developed using gas chromatography coupled to mass spectrometry. Six MNTs were selected as target compounds for neurotoxicity testing. MNTs underwent a two-step derivatization with hexamethyldisilazane (HDMS) for O-silylation followed by N-methyl-bis-heptafluorobutyramide (MBHFBA) for N-perfluoroacylation. Derivatization conditions were optimized by an experimental design approach. Method validation showed linear calibration curves (r ² > 0.9976) in the range of 1-100 ng for all the compounds. The recovery rates were between 92 and 119%. The method was repeatable and reproducible with relative standard deviations (RSD) in the range of 2.5-9.3% for intra-day and 4.8-12% for inter-day variation. The limits of detection and the limits of quantitation were 0.4-0.8 and 1.2-2.7 ng/mL, respectively. The method was successfully applied to detect and quantify trace levels of MNTs in 5-day-old zebrafish larvae that were exposed to low concentrations of neurotoxic chemicals such as pesticides and methylmercury. Although visual malformations were not detected, the MNT levels varied significantly during early zebrafish development. These results show that exposure to neurotoxic chemicals can alter neurotransmitter levels and thereby may influence early brain development. Graphical abstract ᅟ.

Recognition and selective adsorption of pesticides by superparamagnetic molecularly imprinted polymer nanospheres

Selective adsorption of pesticides phosalone, diazinon, and chlorpyrifos from aqueous solution by superparamagnetic molecularly imprinted polymer nanosphere.

Polymer–nanoparticles composites in bioanalytical sample preparation

The term composite refers to a class of synthetic materials made from different constituents which exhibit final properties which are different from those of the individual components. Composites have been extensively used in the sample treatment context as sorbents since the resulting solid presents better extraction efficiency. In this realm, polymeric nanocomposites are raised as a powerful alternative. They can be tailored-synthesized for selectivity enhancement or include a magnetic core to simplify the extraction/elution process. This review article points out the relevance of such nanomaterials in bioanalysis. Several synergic combinations of nanoparticles (magnetic, carbon-based) as well as polymeric coatings (conventional, conductive or molecularly imprinted) are commented on. Finally, the potential of biopolymers in the microextraction field is briefly highlighted.

Two-photon excited quantum dots with compact surface coatings of polymer ligands used as an upconversion luminescent probe for dopamine detection in biological fluids

Two-photon excited CdTe quantum dots were developed as a novel upconversion luminescent probe for dopamine detection in biological fluids.