Separation and determination of norepinephrine, epinephrine and isoprinaline enantiomers by capillary electrophoresis in pharmaceutical formulation and human serum

Activatable NIR Fluorescence Probe for Epinephrine Detection and Bioimaging Based on Anionic Heptamethine Cyanine

Epinephrine (EP) is an essential catecholamine in the human body. Currently, most EP detection methods are not suitable for in vivo detection due to material limitations. An organic small molecule fluorescent probe based on a chemical cascade reaction for the detection of EP was designed. Anionic heptamethine cyanine dye was selected as a fluorescent dye because of its NIR fluorescence emission with excellent biocompatibility. The secondary amine of EP nucleophilically attacks the carbonate of the probe with its stronger nucleophilicity and further undergoes intramolecular nucleophilic cyclization to release the fluorophore. Other substances containing only primary amines or no β-OH lack reaction competitiveness due to their weaker nucleophilicity or inability to undergo further cyclization. The fluorescence recovery of the probe was linearly related to the EP concentration of 2-75 μmol/L. The detection limit was 0.4 μmol/L. The recovery rate was 94.78-111.32%. Finally, we successfully achieved bioimaging of EP in living cells and EP analogue in nematodes.

Deep eutectic solvents combined with beta-cyclodextrin derivatives for chiral separation of typical adrenergic receptor agonists by capillary electrophoresis with amperometric detection

Enantioseparation has always been one of the research hotspots and difficulties in the field of modern separation science. In this work, a binary chiral electrophoretic separation system was constructed using deep eutectic solvents (DESs) coupled with beta-cyclodextrin derivatives based on capillary electrophoresis with amperometric detection system, and five groups of typical adrenergic receptor agonists (adrenaline, salbutamol, isoproterenol, norepinephrine and terbutaline) were selected as the model enantiomers. The effects of additive types and contents of DESs and cyclodextrins, and the pH value and concentration of the running buffer on the resolution of the selected chiral compounds were investigated in detail. The mechanism of DESs improving separation was explored preliminarily by means of UV spectrophotometry, which was further verified based on the comparison of single and mixed components of choline chlorine-urea DES. Under the optimum conditions, the relative standard deviations for inter-day and intra-day repeatability of the migration time, peak area and resolution for adrenaline and salbutamol were within 8.7%, and the limits of detection reached 0.030 μg mL-1 (S/N = 3). The recovery data were in the range of 96.3-118.7%. The developed methods have been applied for the analyses of (+)-adrenaline hydrochloride injection and (±)-salbutamol aerosol. This binary chiral electrophoretic separation system by CE-AD has high detection sensitivity and low analytical cost, providing an alternative for the separation and analysis of chiral drugs.

High-performance fluorescence probe for fast and specific visualization of norepinephrine in vivo and depression-like mice

Norepinephrine (NE), as an important neurotransmitter, is closely associated with the pathogenesis of anxiety and depressive disorders. Effective monitoring of NE fluctuation aids in the diagnosis of depression and the therapeutic assessment of the antidepressant intervention. The construction of novel fluorescent probes with high specificity towards NE for imaging in depression models is still in demand urgently. In this work, a novel resorufin-based red-emitting fluorescent probe for real-time tracking NE was developed. NE can significantly increase the fluorescence of probe LNE by triggering deprotection of carbonothioate ligand via nucleophilic substitution. The probe LNE demonstrated significant NE selectivity and sensitivity over other analytes in vitro. In addition, probe LNE showed a fast response time (<10 min), and the change in fluorescence signal was positively linked with NE concentration, which could be utilized to track the dysregulation of NE in vivo. More importantly, this powerful probe was successfully employed for real-time visual and imaging of NE in living cells and depression-like behavior animals.

Smart green CQD@SiO2 hybrid coated optical fiber manifesting dual versatile absorptive and MIP features towards epinephrine detection

For the first time, in this study, a novel optical fiber biosensor is proposed and developed via coating only one smart functional layer of silica-supported carbon dots realizing the concepts of both lossy mode resonance (LMR) and molecularly imprinted polymer (MIP) for epinephrine detection. The carbon quantum dots (CQDs) are prepared using a green synthesis method and then treated with a molecularly imprinted polymer (MIP) strategy. Under ultrasonic irradiation, a SiO₂ shell was stabilized on the surface of the CQDs to graft and to provide the LMR/MIP functional layer onto the curved optical fiber surface. Accurate structural and morphological characterization confirmed the carbon quantum dot agents and also the SiO₂ supporting shells on the optical fiber, while spectroscopic analysis confirms the formation of the imprinted polymer and desirable absorbance characteristics. The experimental and numerical sensing studies revealed that the proposed sensing probe allows the rapid adsorption/desorption of epinephrine to the sensing films and highly permeable coating for studying the influence of effective parameters. Under the optimal experimental conditions, the sensitivity of the proposed LMR-based optical fiber sensor is reported to be 0.37 nm μM^-1 with a correlation coefficient of 0.99. So, sensitive detection of epinephrine at a low concentration can be guaranteed with a 0.72 mM LOD.

Enhanced sensitivity of dilute aqueous adrenaline solution with an asymmetric hexagonal ring structure in the terahertz frequencies

Quantitative detection of neurotransmitters in aqueous environment is crucial for the early diagnosis of many neurological disorders. Terahertz waves, as a non-contact and non-labeling tool, have demonstrated large potentials in quantitative biosensing. Although the detection of trace-amount analyte has been achieved with terahertz metamaterials in the recent decades, most studies have been focused on dried samples. Here, a hexagonal asymmetric metamaterial sensor was designed and fabricated for aqueous solution sensing with terahertz waves in the reflection geometry. An absorption enhancement of 43 was determined from the simulation. Dilute adrenaline solutions ranging from 30 µM to 0.6 mM were measured on our sensor using a commercial terahertz time-domain spectroscopy system, and the effective absorption was found to be linearly correlated with the concentration (R²= 0.81). Furthermore, we found that as the concentration becomes higher (>0.6 mM), a non-linear relationship starts to take place, which confirmed the previous theory on the extended solvation shell that can be probed on the picosecond scale. Our sensor, without the need of high-power and stable terahertz sources, has enabled the detection of subtle absorption changes induced by the solvation dynamics.

Synthesis of porous 2D layered nickel oxide-reduced graphene oxide (NiO-rGO) hybrid composite for the efficient electrochemical detection of epinephrine in biological fluid

In the present research work, 2D-Porous NiO decorated graphene nanocomposite was synthesized by hydrothermal method to monitored the concentration of epinephrine (EPI). The morphology (SEM and TEM) results confirmed 2D-Porous NiO nanoparticles firmly attached over graphene nanosheets. FTIR and XPS analysis confirmed the formation of nickel oxide formation and complete reduction of GO to rGO. The electrochemical activity of the proposed NiO-rGO/GCE modified electrode on epinephrine was analyzed by simple cyclic voltammetry technique. The proposed low cost NiO-rGO/GCE modified electrode showed excellent catalytic activity over GCE and rGO/GCE electrodes. Due to its high conductivity and charge transfer ability of the NiO-rGO/GCE modified electrode exhibited high sensitivity of EPI at optimized conditions. The anodic peak current of the EPI linearly increases with increasing the concertation of EPI. A wide linear range (50 μM-1000 μM) was achieved with high correlation coefficient (R² = 0.9986) and the limit of detection (LOD) of NiO-rGO/GCE modified electrode was calculated to be 10 μM. NiO-rGO/GCE electrode showed good stability and repeatability towards the EPI oxidation. Mainly, the proposed NiO-rGO/GCE modified electrode showed good sensitivity of EPI in the human biological fluid with high recovery percentage. The low cost, NiO-rGO/GCE electrode could be the promising sensor electrode for the detection of Epinephrine in the real samples.

Single-Drop Analysis of Epinephrine and Uric Acid on a Screen-Printed Carbon Electrode

This work demonstrates the analysis of epinephrine (EP) and uric acid (UA) in a single drop (the volume of the test solution was only 50 µL) using a screen-printed carbon electrode (SPCE) sensor and square-wave voltammetry (SWV). The limit of detection, limit of quantification, linearity, accuracy, precision, and robustness were validated. The normality of the experimental data was tested and confirmed for both methods. Heteroscedasticity was checked by residual analysis followed by a statistical F-test. The latter was confirmed for both analytes. The low relative standard deviations (RSD) at all calibration points and repetitive slopes justified the use of a calibration curve; therefore, the standard addition methodology was avoided (the latter is common in electroanalysis, but time-consuming). Since the conditions for using an ordinary least squares (OLS) regression were not met, weighted linear regression (WLR) was used to improve the accuracy of the analytical results at low concentrations of the analytes. In this manner, the best weighted model was determined and used for the quantification. A comparison was made between the OLS and WLR methods to show the necessity of using the WLR method for EP and UA analysis. The newly developed and validated methods were also shown to be effective in the analysis of real samples. The content of EP in an EP auto-injector and UA in human urine was tested by employing the best weighted model. For EP and UA, the accuracy in terms of the average recovery value was 101.01% and 94.35%, and precision in terms of RSD was 5.65% and 2.75%, respectively. A new analytical methodology is presented that uses a low volume (a single drop), and it offers the advantage of electroanalysis for on-site analysis, where conventional chromatographic techniques cannot be easily employed. Furthermore, the developed technique has additional advantages in terms of speed, cost, and miniaturization.

Enantioseparation of phenethylamines by using high-performance liquid chromatography column permanently coated with methylated β-cyclodextrin

Cyclodextrins and their derivatives have been used for chiral high-performance liquid chromatography selectors, while they are costly to use as mobile phase additives in high-performance liquid chromatography. Here, we report application of phenyl column coated permanently with methylated β-cyclodextrin for chiral high-performance liquid chromatography. A 0.1% (v/v) phosphoric acid solution containing 1 M NaCl and 0.5% (w/v) methylated β-cyclodextrin was subjected to a phenyl column at a flow rate of 0.5 mL/min at 30°C for 2 h. Using the precoating phenyl column, all the enantiomers of the four phenethylamines (norepinephrine, epinephrine, octopamine, and synephrine) were successfully separated simultaneously by high-performance liquid chromatography with a mobile phase without methylated β-cyclodextrin at a flow rate of 0.2 mL/min at 30°C. The enantioseparation ability was retained for successive analyses during 1 week. It is suggested that inclusion complex of methylated β-cyclodextrin with a phenyl group on the surface of the stationary phase could be formed and that the inclusion complex could form the ternary complex with the injected analytes. The longer retention time of (S)-enantiomers of analytes than corresponding (R)-enantiomers for high-performance liquid chromatography could be explained from the higher stability of the methylated β-cyclodextrin complexes with (S)-enantiomers, which were confirmed by capillary electrophoresis and ¹ H NMR spectroscopy experiments.

Response Surface Methodology for Spectrophotometric Determination of Two β-Adrenergic Agonists-Terbium Chemosensors in Urine and Pharmaceutical Dosage Forms

BACKGROUND

According to literature reports, none of the previous methods of analysis had touched the multivariate approach for the quantification of significant factors affecting the interaction of dobutamine or hexoprenaline with Terbium.

OBJECTIVE

Two novel β-adrenergic agonists-lanthanide chemosensors were prepared for the determination of dobutamine and hexoprenaline in their pure and pharmaceutical dosage forms and in urine samples. Fabrication of the two chemosensors was based on their ligand-metal interaction with the lanthanide Terbium.

METHODS

A Plackett-Burman Design (PBD) was selected for the screening of four main variables (reaction time, metal volume, pH, and temperature). Applying Response Surface Methodology (RSM), a Central Composite Design (CCD) was executed for the optimization of the significant factors with narrower upper and lower limits. Spectrophotometric technique was exploited for the analysis of the two chemosensors.

RESULTS

Maximum absorption was obtained at 299 and 298 nm for dobutamine-terbium and hexoprenaline-terbium complexes, respectively. Only factors that were found to bear significant effects on the formed complexes were promoted to the optimization level. Model verification was carried out, where target results coincided with those at the predicted levels, indicating the efficiency of the two proposed models. Validation of the proposed was implemented and linear ranges were found to be 3.30-13.50 and 1.90-10.00 µg/mL, for dobutamine and hexoprenaline, respectively.

CONCLUSIONS

Recovery and relative standard deviation values by application in pure powder, pharmaceutical dosage forms and spiked urine samples indicated high accuracy and reproducibility. Wide-ranging linear values and comparatively low detection limits inferred the effectiveness of the proposed method.

HIGHLIGHTS

RSM for optimization of spectrophotometric determination of dobutamine and hexoprenaline β-adrenergic agonists-lanthanide chemosensors; PBD was used for screening and CCD for optimization of variables affecting the spectrophotometric method; Determination of dobutamine and hexoprenaline in pure powder, pharmaceutical dosage form, and spiked urine samples was accomplished after method validation.

CuO nanorods as a laccase mimicking enzyme for highly sensitive colorimetric and electrochemical dual biosensor: Application in living cell epinephrine analysis

A sensitive colorimetric and electrochemical sensor for measuring of epinephrine (EP) was developed based on CuO nanorods (NRs), and applicability of the sensor for detection of release epinephrine (EP) from living cells was evaluated. The CuO NRs was prepared using a facile and efficient method in low temperature and characterized by Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and Energy-dispersive X-ray spectroscopy (EDX). The CuO NRs exhibited laccase-like activity and could oxidize epinephrine (EP) to a colored product. No interference from the common interfering agents such as dopamine, ascorbic acid and uric acid was observed. Colorimetric sensor demonstrated a linear range of 0.6-18 μM with detection limit of 0.31 μM. Furthermore, the electrochemical study showed CuO NRs exhibited excellent electrocatalytic activity towards epinephrine oxidation. Differential pulse voltammetry signals increase with increasing of EP concentration in the range 0.04-14 μM, with a detection limit of 20 nM. Finally, the proposed sensor applied to perform real-time monitoring of epinephrine released by PC12 cells, indicating that CuO NRs provide a new platform for developing high-performance sensors in biological applications.

Au Quantum Dot/Nickel Tetraminophthalocyanaine-Graphene Oxide-Based Photoelectrochemical Microsensor for Ultrasensitive Epinephrine Detection

Owing to the importance of epinephrine as a neurotransmitter and hormone, sensitive methods are required for its detection. We have developed a sensitive photoelectrochemical (PEC) microsensor based on gold quantum dots (Au QDs) decorated on a nickel tetraminophthalocyanine-graphene oxide (NiTAPc-Gr) composite. NiTAPc was covalently attached to the surface of graphene oxide to prepare NiTAPc-Gr, which exhibits remarkable stability and PEC performance. In situ growth of Au QDs on the NiTAPc-Gr surface was achieved using chemical reduction at room temperature. The synthesized materials were characterized by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and electrochemical impedance spectroscopy. Au QDs@NiTAPc-Gr provided a much greater photocurrent than NiTAPc-Gr, making it suitable for the ultrasensitive PEC detection of epinephrine. The proposed PEC strategy exhibited a wide linear range of 0.12-243.9 nM with a low detection limit of 17.9 pM (S/N = 3). Additionally, the fabricated PEC sensor showed excellent sensitivity, remarkable stability, and good selectivity. This simple, fast, and low-cost strategy was successfully applied to the analysis of human serum samples, indicating the potential of this method for clinical detection applications.

Electrochemical sensor based on incorporation of gold nanoparticles, ionic liquid crystal, and β-cyclodextrin into carbon paste composite for ultra-sensitive determination of norepinephrine in real samples

A novel, reliable electrochemical sensor is fabricated for direct and sensitive determination of norepinephrine (NE) based on gold nanoparticles, ionic liquid crystal, and β-cyclodextrin modified carbon paste electrode, namely AuILCCDCPE. The ionic liquid crystal (ILC) played a key role in improving the current response of electro-oxidation of NE compared with other ionic liquids modified electrodes. The ILC increased the ionic conductivity of the paste and formed noncovalent interactions with both host (CD) and guest (NE) compounds. The solid state structure of the ILC helped in the formation of ordered films in the paste. Furthermore, CD and Au nanoparticles raised the stability and the electrocatalytic ability of the proposed sensor. Under optimized conditions, the fabricated electrochemical sensor showed a good electrochemical response towards NE in human urine in the linear dynamic ranges of 0.05–10 μmol/L and 20–300 μmol/L with a correlation coefficient of 0.999 and detection limit of 3.12 × 10−9 mol/L in the low concentration range. The practical analytical performance of the sensor was attained for determination of NE in real samples with satisfied recovery results. This sensor has great ability to be extended for electrochemical applications in assays of other drugs.

Preparation of Molecularly Imprinted Magnetic Graphene Oxide-Gold Nanocomposite and Its Application to the Design of Electrochemical Sensor for Determination of Epinephrine

In this study, a new molecularly imprinted polymer (MIP) based nanocomposite was synthesized then used to determine epinephrine (EPN) by the use of an electrochemical sensor modified by it. Typical techniques for the synthesis of MIP have disadvantages, such as weak binding sites, low mass transfer and low selectivity. One of the ways to improve electrochemical properties is the use of graphene oxide (GR-Ox) and modification of its surface. For this purpose, GR-Ox was initially magnetized (MGR-Ox), then its surface was coated with a silica layer, and gold nanoparticles (AuNPs) were coated on its surface. Subsequently, copolymerization of methacrylic acid (MAA) and N,N'-methylene-bis-acrylamide (MBA) in the presence of EPN was performed on the MGO-AuNPs surface. Afterwards, a selective carbon paste electrode (CPE) with synthetic nanocomposite was fabricated to detect EPN. Under optimal conditions, a linear range from 10^-8 to 5.0 × 10^-7 M was obtained for the measurement of EPN in urine and blood with a detection limit of 5 × 10^-9 M (S/N = 3).

Simple strategy for sensitive detection of dopamine using CdTe QDs modified glassy carbon electrode

BACKGROUND

Cellular and brain metabolism of dopamine can be correlated with a number of neurodegenerative disorders, our study was to explore a simple and efficient method to detect dopamine in real samples.

METHODS

A new quantum dots (CdTe QDs) could be prepared using the hydrothermal method, the electrochemical biosensor was established by dropping CdTe QDs on the surface of glassy carbon electrode (GCE).

RESULTS

The CdTe QDs/GCE exhibited the excellent electrochemical catalytic activity toward dopamine (DA) with good stability and high sensitivity in presence of interfering substances. The detection limit of DA was calculated by differential pulse voltammetry (DPV) as low as 0.3 μmol L^-1 with a linear dynamic range of 1 μmol L^-1 to 400 μmol L^-1 .

CONCLUSION

In this paper, the proposed electrochemical biosensor could be effectively used for the direct and rapid detection of DA in human serum and urine samples.

Colorimetric detection of epinephrine using an optimized paper-based aptasensor

Morphological modification of gold nanoparticles to obtain a highly efficient paper based sensor for colorimetric detection of epinephrine (LOD – Limit of Detection).

Ultra-sensitive determination of epinephrine based on TiO2-Au nanoclusters supported on reduced graphene oxide and carbon nanotube hybrid nanocomposites

A highly efficient and sensitive electrochemical sensor for EP based on reduced graphene and multi-walled carbon nanotube hybrid nanocomposites loaded TiO2-Au nano-clusters modified glassy carbon electrode was developed. The surface nature and morphology of the nanocomposite film and the electrochemical properties of the sensor were characterized by Raman spectra, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectra (EDX), Fourier transform infrared spectroscopy (FT-IR), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), respectively. Carbon nanomaterials were widely used in sensing due to its large electroactive surface area, fast electron transport and strong adsorption capacity. Meanwhile, TiO2-Au nano-clusters could accelerate the electron transfer, increase reactive site and extend electrochemical response window. The nanocomposite film could greatly enhance the response sensitivity and decrease the overpotential. The resulting sensor showed an excellent electrocatalytic activity toward EP. Under the optimum conditions (i.e. pH6.0, 0.1M PBS, preconcentration for 110s), Differential pulse voltammetry was employed to detect ultra-trace amounts of EP. The result of a wide linear range of 1.0-300nM and limited of detection 0.34nM (S/N=3) were obtained. The constructed sensor exhibited excellent accuracy and precision, the relative standard deviation (RSD) was less than 5%. The nanocomposite film sensor was successfully used to accurately detect the content of EP in practical samples, and the recoveries for the standards added are 97%-105%.

Enantioseparation of the constituents involved in the phenylalanine-tyrosine metabolic pathway by capillary electrophoresis tandem mass spectrometry

Catecholamines dopamine, norepinephrine, and epinephrine are well-known neurotransmitters playing different roles in the nervous and endocrine system. These compounds are biologically synthesized in the phenylalanine-tyrosine pathway which consists on the successive conversion of l-phenylalanine into l-tyrosine, l-3,4-dihydroxyphenylalanine (L-DOPA), dopamine, norepinephrine, and epinephrine. This work describes the development of an enantioselective CE-ESI-MS² methodology enabling, for the first time, the simultaneous enantioseparation of all the constituents involved in the Phe-Tyr metabolic pathway, since all these compounds except dopamine are chiral. The developed method was based on the use of a dual CDs system formed by 180mM of methyl-β-CD and 40mM of 2-hydroxypropyl-β-CD dissolved in 2M formic acid (pH 1.2) and presented the advantage of avoiding the use of any time-consuming labelling procedure. LODs ranged from 40 to 150nM and the unequivocal identification of the compounds investigated was achieved through their MS² spectra. The applicability of this methodology to the analysis of biological samples (rat plasma) was also demonstrated.

A biosensor based on gold nanoparticles stabilized in poly(allylamine hydrochloride) and decorated with laccase for determination of dopamine

A new biosensor for dopamine determination based on laccase immobilized in gold nanoparticles is reported.

Development of glassy carbon electrode modified with ruthenium red-multiwalled carbon nanotubes for simultaneous determination of epinephrine and acetaminophen

A glassy carbon electrode modified with ruthenium red and functionalized multi-walled carbon nanotube has been developed. The electrochemical response characteristics of the modified electrode toward epinephrine (EP) and acetaminophen (AC) was investigated by differential pulse voltammetry (DPV). Linear calibration plots were obtained over the range of 0.3 - 333.3 μM for both EP and AC with sensitivities of 0.221 and 0.174 μA μM(-1) for EP and AC, respectively. The detection limits for EP and AC were 0.04 and 0.06 μM, respectively. The diffusion coefficients for the oxidation of EP and AC at the modified electrode were calculated as 2.74 ± 0.05 × 10(-5) and 1.75 ± 0.07 × 10(-5) cm(2) s(-1), respectively. The practical analytical utilities of the modified electrode were demonstrated by the determination of EP and AC in human urine and serum as well as AC tablet samples.