Interfacial SERS Analyzer Based on Silver Nanoparticles Array for In vivo Monitoring of 5-Hydroxytryptamine in Rat Brain Microdialysates and Serum

Simultaneous determination of 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyamphetamine (MDA) in rat blood and brain microdialysates by high-performance liquid chromatography with fluorescence detection (HPLC-FL) was developed. Microdialysates were directly subjected to derivatization with 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl). The DIB-derivatives of MDMA, MDA and the internal standard, 1-methyl-3-phenylpropylamine (MPPA), were isocratically separated on an ODS column using a mixture of 50 mm phosphate buffer (pH 7.0)-acetonitrile-methanol-2-propanol (50:45:5:2, v/v/v/v %) as an eluent at a flow rate of 1.5 mL/min. The calibration curves of MDA and MDMA spiked to blood and brain microdialysates were linear over the ranges 2.5-500 and 5.0-1000 ng/mL, respectively. The detection limits of MDA and MDMA were 1.2 and 4.2 for blood and 1.3 and 4.8 ng/mL for brain, respectively. Additionally, the intra- and the inter-assay precisions were lower than 5.6% for the blood and brain microdialysates (n = 4). The proposed method was successfully applied for the monitoring of MDMA and its metabolite MDA in rat blood and brain microdialysates, and the pharmacokinetic parameters of MDMA and MDA in the microdialysates after administration of MDMA (5 mg/kg, i.p.) with or without caffeine (20 mg/kg, i.p.) were evaluated.

Neurochemical effects of chronic haloperidol and lithium assessed by brain microdialysis in rats

Metabolic profiling of body fluids from small animal models is often used in (translational) biological studies in order to obtain insight into the underlying molecular mechanisms of (complex) diseases. An example is the use of brain microdialysis samples from rats to study neurological disorders by means of a metabolomics approach. From an analytical point of view, the profiling of (endogenous) metabolites in rat brain microdialysates is challenging because of the limited sample volume for both sample preparation and injection, notably in longitudinal studies. In this work, we have assessed the analytical performance of capillary electrophoresis-mass spectrometry (CE-MS) for the direct profiling of endogenous metabolites in rat brain microdialysates, i.e. without using any sample preparation or derivatization. An on-line preconcentration procedure with sample stacking, which was fully compatible with the high-salt concentration in microdialysates, was used to significantly improve the detection sensitivity of the CE-MS method for metabolic profiling. A response surface methodology, applying a Box-Behnken design, was considered to determine the optimal conditions for preconcentration. A linear response (R2>0.99) for selected metabolites in the concentration range from 0.05 to 10 µM was obtained in perfusate samples. Interday RSD values for peak area and migration time were 2.6-19% and below 3.8%, respectively. Limits of detection ranged from 11 to 284 nM when employing an injection volume of about 291 nL, corresponding to 17% of the total capillary volume. The utility of the CE-MS approach was demonstrated by the direct profiling of endogenous metabolites in rat brain microdialysates. At least 48 compounds could be analyzed of which 25 were provisionally identified and quantified.

A method for the analysis of intact glucuronides and sulfates of common neurotransmitters serotonin (5-HT) and dopamine (DA) as well as of 5-hydroxy-3-indoleacetic acid (5-HIAA), 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) in rat brain microdialysates by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. Enzyme-assisted synthesis using rat liver microsomes as a biocatalyst was employed for the production of 5-HT-, 5-HIAA-, DOPAC-, and HVA-glucuronides for reference compounds. The sulfate conjugates were synthesized either chemically or enzymatically using a rat liver S9 fraction. The LC-MS/MS method was validated by determining the limits of detection and quantitation, linearity, and repeatability for the quantitative analysis of 5-HT and DA and their glucuronides, as well as of 5-HIAA, DOPAC, and HVA and their sulfate-conjugates. In this study, 5-HT-glucuronide was for the first time detected in rat brain. The concentration of 5-HT-glucuronide (1.0-1.7 nM) was up to 2.5 times higher than that of free 5-HT (0.4-2.1 nM) in rat brain microdialysates, whereas the concentration of DA-glucuronide (1.0-1.4 nM) was at the same level or lower than the free DA (1.2-2.4 nM). The acidic metabolites of neurotransmitters, 5-HIAA, HVA, and DOPAC, were found in free and sulfated form, whereas their glucuronidation was not observed.

Liquid chromatography with amperometric detection remains the most widely used method for acetylcholine quantification in microdialysis samples. Separation of acetylcholine from choline and other matrix components on a microbore chromatographic column (1 mm internal diameter), conversion of acetylcholine in an immobilized enzyme reactor and detection of the produced hydrogen peroxide on a horseradish peroxidase redox polymer coated glassy carbon electrode, achieves sufficient sensitivity for acetylcholine quantification in rat brain microdialysates. However, a thourough validation within the concentration range required for this application has not been carried out before. Furthermore, a rapid degradation of the chromatographic columns and enzyme systems have been reported. In the present study an ion-pair liquid chromatography assay with amperometric detection was validated and its long-term stability evaluated. Working at pH 6.5 dramatically increased chromatographic stability without a loss in sensitivity compared to higher pH values. The lower limit of quantification of the method was 0.3 nM. At this concentration the repeatability was 15.7%, the inter-day precision 8.7% and the accuracy 103.6%. The chromatographic column was stable over 4 months, the immobilized enzyme reactor up to 2-3 months and the enzyme coating of the amperometric detector up to 1-2 months. The concentration of acetylcholine in 30 μl microdialysates obtained under basal conditions from the hippocampus of freely moving rats was 0.40 ± 0.12 nM (mean ± SD, n = 30). The present method is therefore suitable for acetylcholine determination in rat brain microdialysates.

Quantitative analysis of olanzapine in rat brain microdialysates by HPLC–MS/MS coupled with column-switching technique

Quantification of serine enantiomers in rat brain microdialysate using Marfey's reagent and LC/MS/MS

A rapid and reproducible method has been developed for the simultaneous quantification of dopamine (DA), norepinephrine (NE), and serotonin (5-HT) in rat brain microdialysates. Derivatization was processed through reductive amination with butyraldehyde and sodium cyanoborohydride at 60℃ for 80 min incubation. Dibutylated monoamine neurotransmitters (MANTs) were directly analyzed with ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The chromatographic run time was shorter (2.1 min/sample) than previous studies [15] [18] [20]. Good linearity (R2 > 0.99) was obtained for DA, NE and 5-HT in the range of 25 - 5000 pg/mL, 5 - 1000 pg/mL and 2.5 - 500 pg/mL, respectively. Acceptable precision (CV, 8.5% - 13.4%) as well as accuracy (recovery, 94.1% - 106.8%) could be acquired by analysis of six batches of quality control samples (QCs) at four different concentrations, which demonstrated the reliability and reproducibility of current method. This method was successfully applied to the simultaneous determination of DA, NE and 5-HT in rat brain microdialysates, where basal levels as well as elevated levels after dosing with amphetamine (AMPH) were quantified for all three MANTs. This study provides a simple and rapid way to analyze MANTs in the biofluid in the future.

Determination of dopamine, serotonin, biosynthesis precursors and metabolites in rat brain microdialysates by ultrasonic-assisted in situ derivatization–dispersive liquid–liquid microextraction coupled with UHPLC-MS/MS

Biomimetic mesoporous carbon-silica/AAO asymmetric nanochannel array for electrochemical sensing of K+ in rat brain microdialysates and serum

Determination of donepezil hydrochloride in human and rat plasma, blood and brain microdialysates by HPLC with a short C 30 column

Emissive carbon dots derived from natural liquid fuels and its biological sensing for copper ions

Single pump column switching technique employing a flow gradient and wavelength programmed fluorescence for simultaneous monitoring of serotonin, fluoxetine and norfluoxetine in rat brain microdialysate

Semi-micro column HPLC of triazolam in rat plasma and brain microdialysate and its application to drug interaction study with itraconazole

For the reliable determination of trace chemicals in the brain, we created a SERS platform based on a functionalized AuNPs array formed at a liquid/liquid interface in a uniform fashion over a large substrate area through ternary regulations for real‐time quantification of trace norepinephrine (NE). The rigid molecule, 4‐(thiophen‐3‐ylethynyl)‐benzaldehyde (RP1) was designed and co‐assembled at AuNPs with 4‐mercaptophenylboronic acid (MPBA) to chemically define NE via dual recognition. Meanwhile, the rigid structure assembly of RP1 and MPBA efficiently fixed the interparticle gap, guaranteeing reproducible SERS analysis. Furthermore, the Raman peak of C≡C group in the silent region was taken as a response element to further improve the accuracy. Combined with microdialysis, this SERS platform was developed for in‐the‐field testing of NE in rat brain microdialysates following anxiety.