Spectroscopic Measurements of Physiological Elements in Microdialysis Samples from Rat Brain,Flowering Plum Fruit and Pea

The basal levels of magnesium and copper in rat brain and flowering plum fruit dialysates, and the background concentration of calcium in pea dialysates have been determined with sensitive spectroscopic techniques including atomic absorption spectrometry and spectrophotometry based on amino G acid chlorophosphonazo. It is found that the magnesium level in flowering plum fruit dialysates is much lower than that in rat brain dialysates, indicating a considerable composition difference present between a plant dialysate and an animal one.

Prediction of rat liver transplantation outcomes using energy metabolites measured by microdialysis

Background: Warm ischemia jeopardizes graft quality and recipient survival in donation after cardiac death(DCD) transplantation. Currently, there is no system to objectively evaluate the liver quality from DCD. The present study tried to use energy metabolites to evaluate the donor liver quality. Methods: We divided 195 Sprague-Dawley rats into five groups: the control( n = 39), warm ischemic time(WIT) 15 min( n = 39), WIT 30 min( n = 39), WIT 45 min( n = 39), and WIT 60 min( n = 39) groups. Three rats from each group were randomly selected for pretransplant histologic evaluation of warm ischemiarelated damage. The remaining 36 rats were randomly divided into donors and recipients of 18 liver transplantations, and were subjected to postoperative liver function and survival analyses. Between cardiac arrest and cold storage, liver energy metabolites including glucose, lactate, pyruvate, and glycerol were measured by microdialysis. The lactate to pyruvate ratio(LPR) was calculated. Results: The changes in preoperative pathology with warm ischemia were inconspicuous, but the trends in postoperative pathology and aminotransferase levels were consistent with preoperative energy metabolite measurements. The 30-day survival rates of the control and WIT 15, 30, 45, and 60 min groups were 100%, 81.82%, 76.92%, 58.33%, and 25.00%, respectively. The areas under the receiver operating characteristic curves of glucose, lactate, glycerol, and LPR were 0.87, 0.88, 0.88, and 0.92, respectively. Conclusion: Glucose, lactate, glycerol, and LPR are predictors of graft quality and survival outcomes in DCD transplantation.

EFFECTS OF TRANSIENT FOREBRAIN ISCHEMIA AND RADIX SALVIAE MILTIORRHIZAE (RSM) ON EXTRACELLULAR LEVELS OF MONOAMINE NEUROTRANSMITTERS AND METABOLITES IN THE GERBIL STRIATUM-An in vivo Microdialysis Study

The aim of this study was to investigate the effect of 30 min forebrain ischemia, followed by 120 min reperfusion on extracellular fluid (ECF) levels of dopamine (DA), norepinephrine (NE), serotonin (5-HT) and their metabolites, homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the striatum of gerbils, so as to obtain further information on the mechanism of Radix Salviae Miltiorrhizae (RSM)-induced neuroprotection. Microdialysis was used to sample the extracellular space. Dialysate was measured by high performance liquid chromatography with electrochemical detector (HPLC-ED). ECF DA, NE levels increased from basal levels by 282, 227 and 221 folds, by 9.14, 8.51 and 8.25 folds, respectively for the three ischemic duration (0-10; 11-20; 21-30 min). ECF DA, NE, 5-HT levels in the RSM-treated group were significantly decreased as compared with those in the control group during ischemia (P

Recovery rates of combination antibiotic therapy using in vitro microdialysis simulating in vivo conditions

Microdialysis is a technique used to measure the unbound antibiotic concentration in the interstitial spaces, the target site of action. In vitro recovery studies are essential to calibrating the microdialysis system for in vivo studies. The effect of a combination of antibiotics on recovery into microdialysate requires investigation. In vitro microdialysis recovery studies were conducted on a combination of vancomycin and tobramycin, in a simulated in vivo model. Comparison was made between recoveries for three different concentrations and three different perfusate flow rates. The overall relative recovery for vancomycin was lower than that of tobramycin. For tobramycin, a concentration of 20μg/mL and flow rate of 1.0μL/min had the best recovery. A concentration of 5.0μg/mL and flow rate of 1.0μL/min yielded maximal recovery for vancomycin. Large molecular size and higher protein binding resulted in lower relative recoveries for vancomycin. Perfusate flow rates and drug concentrations affected the relative recovery when a combination of vancomycin and tobramycin was tested. Low perfusate flow rates were associated with higher recovery rates. For combination antibiotic measurement which includes agents that are highly protein bound, in vitro studies performed prior to in vivo studies may ensure the reliable measurement of unbound concentrations.

Determination of 6-Mercaptopurine in Rat Blood by Microdialysis Coupled with High Performance Liquid Chromatography on a Functionalized Multi-wall Carbon Nanotubes Modified Electrode

A new chemically modified electrode(CME) immobilized on the surface of multi-wall carbon nanotubes functionalized with carboxylic groups was fabricated. The results indicate that the CME exhibits efficiently electrocatalytic oxidation of 6-mercaptopurine(6-MP). The CME can be used as the working electrode in the liquid chromatography for the determination of 6-MP. The peak current of 6-MP is linearly changed with its concentration ranging from 4.0×10 -7 to 1.0×10 -4 mol/L with the calculated detection limit (S/N=3) of 2.0×10 -7 mol/L. Coupled with microdialysis sampling, the method has been successfully applied to assessing the content of 6-MP in rat blood.

Rapid Determination of Dopamine and Its Metabolites During in vivo Cerebral Microdialysis by Routine High Performance Liquid Chromatography With Electrochemical Detection

To determine dopamine and its metabolites during in vivo cerebral microdialysis by routine high performance liquid chromatography with electrochemical detection. Methods Microdialysis probes were placed into the right striatum of Wistar rat brains and perfused with Ringer＇s solution at a rate of 1.5 pL/min. A reverse phase HPLC with electrochemistry was used to assay DA, DOPAC, and HVA after cerebral microdialysates were collected every 20 minutes from awake and freely moving rats. In order to identify the reliability of this method, its selectivity, linear range, precision and accuracy were tested and the contents of DA, DOPAC, and HVA in rat microdialysates were determined. Results The standard curve was in good linear at the concentration ranging from 74 nmol/L to 1.5 pmol/L for DOPAC （r^2= 0.9996）, from 66 nmol/L to 1.3 gmol/L for DA （r^2=l.0000） and from 69 nmol/L to 1.4 pmol/L for HVA （r^2=0.9992）. The recovery of DOPAC （0.30, 0.77, 1.49 gmol/L）, DA （0,26, 0.69, 1.32 gmol/L）, and HVA （0.27, 0.71, 1.37 gmol/L） was 82.00±1.70%, 104.00±4.00%, 98.70±3.10%; 92.30± 1.50%, 105.30±2.30%, 108.00±2.00%; 80.00±7.80%, 107.69±8.00%, and 108.66±3.10%, respectively at each concentration. Their intra-day RSD was 3.3%, 3.4%, and 2.5%, and inter-day RSD was 4.2%, 2.3%, and 5.6%, respectively. The mean extracellular concentrations of DOPAC, DA, and HVA in rat brain microdialysates were 10.7, 2.4, and 9.2 gmol/L （n=6）, respectively. Conclusion The findings of our study suggested that the simple, accurate and stable method can be applied to basic researches of diseases related to monoamines neurotransmitters by cerebral microdialysis in rats.

Biological Fingerprinting Analysis of Interaction Between Taxoids in Taxus and Microtubule Protein by Microdialysis Coupled with High-performance Liquid Chromatography/Mass Spectrometry for Screening Antimicrotubule Agents

Some natural products, such as traditional Chinese medicines（TCMs）, contain compounds with anticancer activity and have attracted a great interest in recent years as alternative anticancer therapies. A quick and convenient assay for screening antimicrotubule compounds in which in vitro microdialysis/high-performance liquid chromatography （HPLC） is used to monitor the binding of the compounds extracted from TCM Taxus cuspidata Siebold ＆ Zucc（Taxus） to microtubules is reported. It was observed that the extract of Taxus contains at least five compounds which have affinity interaction with microtubules by biological fingerprinting analysis, and they were identified as the taxoids of taxol, baccatin III, 10-deacetylbaccatin Ⅲ（10-DAB）, cephalomannine and 7-epi-10-deacetyltaxol （7-epi-10-DAT） based on the comparison of their high-performance liquid chromatographic/mass spectrometric and UV spectra with those of the standard samples, both assembly-promoting and disassembly-inhibiting characteristics of those compounds were evaluated. It was observed that baccatin Ⅲ and 10-DAB bound to microtubules and the binding degrees were influenced by GTP. Competitive binding behavior of taxol with other four taxoids to microtubules was also investigated.

Microdialysis in awake macaque monkeys for central nervous system pharmacokinetics

Background: The brain bioavailability of novel small molecules developed to address central nervous system disease is classically documented through ex vivo or in vivo analyses conducted in rodent models. Data acquired in rodent models are, however,not easily transferrable to human as the pharmacokinetic and pharmacodynamics profiles of the species are quite different.Methods: Using drugs selected for their differential transport across the blood-brain barrier, we here demonstrate the feasibility of brain microdialysis in normal vigil macaque monkey by measuring brain extracellular fluid bioavailability of carbamazepine, digoxin, oxycodone, and quinidine.Results: All drugs, but digoxin, were found in dialysate samples. Drugs that are substrate of P-glycoprotein show a difference of bioavailability or brain pharmacokinetic parameters between rodents and primates.Conclusion: Data suggest that brain microdialysis in vigil macaque monkey, the species of choice for classic pharmacokinetic/pharmacodynamics studies could help predicting human brain bioavailability of a small molecule depending on the protein involved in the efflux transport from the brain.

Evaluation of the Effects of Corticosteroids on Histamine Release by ex Vivo Cutaneous Microdialysis

The purpose of the study was to evaluate the effects of corticosteroids on histamine release and to compare their potency with the MacKenzie classification based on their vasoconstrictor effects. Thanks to ex Vivo cutaneous microdialysis, we studied histamine-induced release over a period of time on excised abdominal skin from women. Eight corticosteroids were topically applied with occlusive dressing onto the skin, above probes, before anti-IgE injection. Histamine levels were assessed by an EIA method. In order to compare the different corticosteroids, AUC was calculated allowing an estimation of the amount of released histamine for 60 min of ex vivo cutaneous microdialysis. Diflucortolone 0.1% and micronized betamethasone dipropionate 0.05% are considered as corticosteroids with high potency in MacKenzie classification. Betamethasone dipropionate associated with propylene glycol 0.05%, belongs to a stronger class in Mackenzie classification. Our results showed that the decrease in histamine release was more important with difluocortolone than with both of these corticosteroids. Therefore there was no correlation between the vasoconstrictor potency of topical corticosteroids and their ability to inhibit histamine release.

Characteristics and pharmacokinetics of tripterygium glycosides nano-carries transdermal delivery systems:skin-blood synchronous microdialysis and numerical simulation

The traditional Chinese medicine tripterygium glycosides(TPG)is used clinically to treat some Rheumatism,Eczema,immunosuppression and tumor,with the activities of hypnosis,antipyretic,analgesic,antiinflammatory,allergy and antitumor.However TPG has low water solubility and low skin permeability,so its clinical use is limited.Transdermal delivery systems can provide a controlled drug release rate that can keep constant concentrations of drug in the plasma for up to multiple days,improved patient compliance,and the possibility ofreducing the rate and severity of side effects.In this study,a fast and sensitive technique skin-blood two sites synchronous microdialysis coupled with LC-MS was used to study the pharmacokinetic parameter of three different formulations(TPG nanoemulsion,TPG nanoemulsion based gels and TPG gel).Creating a multilayer model,use the model to simulate the three formulations dynamics in transdermal-drug delivery system.The experiment results showed that the TPG nanoemulsion,TPG nanoemulsion based gels can significantly raise the drug concentrations in skin more than that of TPG gels.The numerical simulation results indicating that TPG gel and TPG nanoemulsion are close to practical measurements,only in the concentration increase phase the numerical simulation result has some difference with the experimental results.TPG nanoemulsion based gels have significant difference with the experimental results,both in concentration increase stage and concentration decreasing stage,but its trend was same.The study shows that the skin-blood synchronous microdialysis technique provided a new method for the pharmacokinetics study of nanocarriers transdermal delivery systems.In addition,the microdialysis technique combined with mathematical modeling provides a very good platform for the further study of transdermal delivery system.

Outcome following severe traumatic brain injury TBI correlates with serum S100B but not brain extracellular fluid S100B:An intracerebral microdialysis study

S100B protein is released by astrocytes into the brain extracellular fluid following acute brain injury and elevated levels in CSF and serum have been shown to correlate with patient outcome following traumatic brain injury. A prospective study of brain extracellular fluid (ECF) and serum S100B levels in 12 patients with severe head injury (GCS ≤ 8) was undertaken using intracerebral microdialysis to investigate whether a correlation with ECF S100B and outcome could be confirmed. Patient outcomes were assessed at 6 months using the Glasgow Outcome Scale (GOS) and divided into two outcome groups: group A, 8 survivors with either a good recovery or moderate disability (GOS scores of 4 or 5);and group B, 4 patients who died (GOS 1). Peak serum levels of S100B were significantly greater in group B (mean 6.03 ng/ml) compared with group A (mean 0.73 ng/ml) (P = 0.009). Group A had a mean peak S100B in the extracellular compartment of 186 ng/ml compared to 150 ng/ml in group B. There was no significant difference between the mean peak brain ECF S100B concentrations for the 2 outcome groups (P = 0.932). We confirm that intracerebral microdialysis can be used to sample S100B concentrations from brain extracellular fluid and our results suggest that the ECF S100B levels were variable and that there was no significant difference between the good outcome and poor outcome groups. In contrast, the serum levels of S100B of patients with a poor outcome were significantly higher than those with a good outcome.

Dynamic Cerebral Microdialysis during Pallidotomy and Thalamotomy in Parkinson’s Disease: A Preliminary Neurochemical Study

In Parkinson’s disease (PD), dopaminergic neurons reduce the regulation of glutamatergic (glutamate-Glu) input from the cortex to neostriatum (caudate and putamen nuclei) consequently leading to a hyperactivity of globus pallidus internae (GPi) neurons that release gamma-amino-butyric acid (GABA) into the thalamic ventrolateral (VL) nucleus. The objective of the present experiment was to measure changes in GABA and Glu in the caudate and the thalamus of 2 patients during the application of electrical stimuli following either a pallidotomy or a thalamotomy. Proper insertion of the electrode was tested by applying high frequency electrical pulses (HFEP). During these procedures, we obtained neurochemical information placing cerebral (CMD) microdialysis probes in caudate nucleus and VL nucleus of ipsi- and contra-lateral thalamus. In VL thalamus, extracellular GABA decreased during HFEP, tending to reach previous levels once HFEP was finalized. Following the pallido- or thalamotomy GABA decreased again. Similarly, in the contralateral VL thalamus, extracellular GABA levels showed a similar but less pronounced profile but did not show any decrement after the lesion. Caudate Glu decreases when HFEP is applied to the GPi and recovers to previous levels after HFEP, but did not decrease again after lesion (GPi-tomy), instead it continued to rise. These results suggest that HFEP exerts a similar but reversible biochemical effect as thermopallido- or thermothalamotomy on GABA extracellular concentration in the ipsilateral VL thalamus. We also observe a distant effect of HFEP, but not of thermolesion, on contralateral thalamic GABA and ipsilateral caudate Glu.

Intracerebral Microdialysis in Neurosurgery for Obsessive-Compulsive Disorder: Report of 2 Preliminary Cases

Neurosurgery for psychiatric disorders, notably for obsessive-compulsive disorder (OCD), was initiated in Venezuela in the decade of 1970, and consisted since that time in the classic stereotactic anterior cingulotomy. In order to know further about the physiopathology of this disorder, we performed intracerebral microdialysis in 2 patients who were operated on. The aim was to measure changes in extracellular neurotransmitters within the basal ganglia. The microdialysis probes were stereotactically placed in the right caudate nucleus and in the dorsomedial nucleus of the right thalamus. The microdialysis was done before the left cingulotomy, during the pause and after the right cingulotomy. Glutamate and gamma-aminobutyric acid (GABA) changes were similar in the caudate nucleus of both patients, whereas in the dorsomedial nucleus the changes were opposite among the 2 patients. Although this study does not bring enough data to explain such differences yet, the existence of dynamic changes in the neurochemistry of the basal ganglia during cingulotomy shows that intracerebral microdialysis can help in the understanding of the pathophysiology of OCD and eventually in the design of new surgeries with better results.

Toosendanin-induced change of dopamine level detected by microdialysis in vivo at rat striatum

To investigate the effect on central nervous transmission of toosendanin (TSN), a presynaptic blocker, rat striatum was perfused in vivo with a TSN-containing artificial cere-brospinal fluid (ACSF) and the level of dopamine (DA) as well as related metabolites in the collected dialysates has been determined by a microbore HPLC with electrochemical detection (mi-crobore HPLC-ECD). The results are as follows: ( i ) TSN induced a biphasic change of DA from its basal level;( ii ) the basal contents of two metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) increased in turn and stayed at a higher level than basal control for a long period. The basal level of 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of 5-hydroxytryptamine(5-HT), had a change similar to that of HVA; (iii) after per-fusion with TSN-containing ACSF, high K+-evoked DA release was inhibited. These results show that TSN does not selectively affect acetylcholine (ACh) release, but probably acts on a common

Comparative study on brain pharmacokinetics of Buyang Huanwu Decoction in normal and cerebral ischemia rats using brain microdialysis combined with LC-MS/MS

Objective To conduct a comparative study on the brain pharmacokinetics of seven ingredients(i.e.senkyunolide A,ferulic acid,formononetin,calycosin,ononin,calycosin-O-β-D-glucopyranoside,and paeoniflorin),which were the compounds of Buyang Huanwu Decoction(BHD),in normal and cerebral ischemia rats administrated intragastrically with BHD.Methods The samples of normal and permanent middle cerebral artery occlusion(pMCAO)rats were collected by using brain microdialysis technique.The concentrations of seven ingredients were determined by the HPLC-MS/MS method.After the BHD were administrated intragastrically to the rats for seven consecutive days,brain microdialysis probes were inserted into the hippocampus of rats,and then the brain microdialysates were collected at 20 min time intervals for 5 h.The separation of the seven ingredients and internal standard(IS)was carried out on an ACQUITY UPLC BEH C18(2.1 mm×100 mm,1.7μm)chromatographic column,using a mobile phase consisting of acetonitrile(containing 0.1%formic acid)and water(containing 0.1%formic acid)for gradient elution within 13 min.The ionization was conducted using an ESI source in positive ion mode.Multiple reaction monitoring mode was used for quantification of ingredients in BHD.Results Linearity,accuracy,precision,matrix effect and stability of LC-MS/MS method were all satisfactory,successfully applied to compare the pharmacokinetics of the analytes between normal and model rats after intragastric administration of BHD.Compared with the normal group,the model group after the administration of the BHD showed that T1/2 of formononetin and ononin were longer,and except for calycosin-O-β-D-glucopyranoside(P<0.01),there was no significant difference between the normal group and the model group.The C_(max) of senkyunolide A and calycosin of model group were increased,while the T_(max) of senkyunolide A was decreased,and except for the T_(max) of PF,the differences between the two groups were statistically significant(P<0.01).Conclusion The LC-MS/MS method combined with microdialysis was successfully applied to the comparative study of brain pharmacokinetics of seven ingredients in BHD.After intragastric administration of BHD,there were differences in the pharmacokinetics of seven ingredients in the brain hippocampus between normal rats and model rats,probably related to the characteristics of the ingredients and the effects of cerebral ischemia on the absorption and distribution of the ingredients.

Pharmacokinetics of different dosage of astragalus membranaceus of buyang huanwu decoction in rats with cerebral ischemic injury by microdialysis combined with LC/MS

To investigate the pharmacokinetics of effective components of Bu Yang Huang Wu Decoction(BYHWD)with different dosages of Astragalus(Yiqi groups and Huoxue groups)applicating in rats with middle cerebral artery occlusion(MCAO).Replicating the animal model of cerebral ischemia-reperfusion in rats,establishing the liquid-mass spectrometry method for the determination of BYHWD and researching the pharmacokinetics of effective components of yiqi groups of BYHWD with different dosages of astragalus(3.09,6.17,12.34 g/Kg)and Huoxue goups(2.32 g/Kg)when applicated seperately in the rats suffering from cerebral ischemia reperfusion injury after femoral vein administration.The pharmacokinetics of formononetin and paeoniflorin in the different dosage groups of BYHWD met the one-compartment model,and the t1/2 of formononetin and paeoniflorin in the low-dose Yiqi and Huoxue groups were(88.43±3.82,69.18±0.11)min,MRT were(138.56±4.83,113.62±2.42)min,and AUC0-twere(28488.35±4800.32,140614.80±23954.05)ng/mL min;The t1/2 of formononetin and paeoniflorin in the middle-dose Yiqi group and Huoxue group were(82.16±1.78,67.08±3.69)min,and MRT were(127.95±2.70,116.58±4.13),AUC0-t were(48619.25±6745.75,159026.00±15003.33)ng/mL min;The t1/2 of formononetin and paeoniflorin in the high-dose Yiqi and Huoxue groups were(80.29±1.12,69.69±0.87)min and MRT was(128.79±1.46,118.78±4.56)min AUC0-twere(109942.90±13101.83,189417.90±22311.00)ng/mL·min.The concentration rate of formononetin t1/2 brain was decreased with increase of Astragalus dose.However,no significant difference between these two variables was found during experiments.Furthermore,the experiments showed that the increasing dose of astragalus would affect the pharmacokinetic behavior of paeoniflorin in the Huoxue groups.More specifically,the result showed that paeoniflorin can be metabolized more slowly in the body when applicated in high dose of the jaundice administration groups.In this way,the effect of paeoniflorin can be lasted for longer time in the body and brain.

Change of extracellular ascorbic acid in the brain cortex following ice water vestibular stimulation： an on-line electrochemical detection coupled with in vivo microdialysis sampling for guinea pigs

Background Ascorbic acid （AA） represents one of the most important enzyme co-factors, antioxidants and neuromodulators and plays an important role in the cerebral system. Increasing evidence has suggested that AA could treat certain kinds of vertigo diseases such as Meniere＇s disease. To elucidate the neurochemical functions associated with AA in vertigo, the change of extracellular AA in the brain cortex following caloric vestibular stimulation （CVS） was evaluated.Methods An on-line electrochemical detection was coupled with in vivo microdialysis to continuously monitor the change of extracellular AA in the primary somatosensory （SI） area of guinea pigs following a caloric vestibular stimulation. Sixteen guinea pigs were divided into three groups, i.e., experimental group with irrigation of the ear canal with ice water （0℃） （n=-8）, and two control groups, one with irrigation of the ear canal with warm water （38℃） （n=-4） and the other with irrigation of the auricle with ice water （n=-4）.Results In the experimental group, the ice water irrigation of the left external ear canal induced a horizontal nystagmus towards the right side lasting about 45 seconds. No nystagmus was induced by warm water irrigation of the external ear canal or by ice water irrigation of the auricle. The extracellular AA concentration significantly increased following the ice water vestibular stimulation, reaching a maximum of （130±20）% （n=8） of the basal dialysate level （2.61±0.92） μmol/L （n=8）, lasting at least for an hour. AA level did not change distinctly after the irrigation of the left external ear canal with warm water or the irriclation of the auricle with ice water.Conclusions The concentration of extracellular AA in the brain cortex of the SI area increased following the ice water vestibular stimulation. This demonstration may be useful for the investigation of the neurochemical processes associated with AA in the process of vertigo.

Monitoring magnesium degradation using microdialysis and fabric-based biosensors

This paper describes the development of a monitoring system capable of detecting the concentration of magnesium ions(Mg^(2+)) released during the degradation of magnesium implants. The system consists of a microdialysis probe that samples fluid adjacent to the implant and a catalytic biosensor specific to Mg^(2+)ions. The biosensor was fabricated on a cotton fabric platform, in which a mixture of glycerol kinase and glycerol-3-phosphate oxidase enzymes was immobilized on the fabric device via a simple matrix entrapment technique of the cotton fibers. Pure magnesium was used as the implant material. Subsequently, the concentration of ions released from the degradation of the magnesium specimen in Ringer's solution was evaluated using cyclic voltammetry technique. The device demonstrated a pseudo-linear response from 0.005 to 0.1 mmol L^(-1) with a slope of 67.48 μA mmol^(-1) L. Detectable interfering species were lesser than 1%indicating a high selectivity of the fabric device. Furthermore,the device requires only 3 μL of fluid sample to complete the measurement compared to spectroscopic method(±50 μL),hence providing a higher temporal resolution and reduced sampling time. The system could potentially provide a real time assessment of the degradation behavior, a new studied aspect in biodegradable metals research.

Amperometric Sensor Based on Neutral Red-Doped Silica Nanoparticles Coupled with Microdialysis for the Measurement of Glutamate in the Rat Striatum

Amperometric sensor based on neutral red-doped silica （NRSiO2） nanoparticles （NPs） was fabricated and coupled with a microdialysis sampling system for the detection of glutamate （Glu） in the rat striatum. The NRSiO2 NPs [about （45 ± 3） nm] were prepared with water-in-oil （W/O） microemulsion method, and characterized by transmission electron microscope （TEM） technique. The neutral red （NR） doped in silica network could maintain its high electroactivity and behave as an excellent electron mediator for electrocatalysis of hydrogen dioxide. Furthermore, the silica surface could prevent the leakage of NR, hence, the stability of biosensor was improved. The novel Glu biosensor showed a linear range from 5.0×10^-7 to 1.5×10^-4 mol/L, with a detection limit of 2.0×10^-7 mol/L （S/N=3）.

Comparative brain pharmacokinetic study of Jiaotai Pills in normal and insomnic rats using brain microdialysis combinated with LC–MS/MS

Objective：To compare the brain pharmacokinetics of five protoberberine-type alkaloids（i.e.berberine,palmatine,coptisine,epiberberine,and jatrorrhizine）,which were the main bioactive constituents of Jiaotai Pills（JTP）,in normal and insomnic rats orally administrated with JTP.Methods：The detection was conducted by a fully validated liquid chromatography-tandem mass spectrometry combinated with brain microdialysis method.Brain microdialysis probes were inserted into the hippocampus of rats.JTP extracts were administrated intragastrically and then brain microdialysates were collected at 30 min time intervals for 10 h.The separation of the five protoberberine-type alkaloids was carried out on a BDS Hypersilusing a mobile phase consisting of acetonitrile and water（containing 5 mmol ammonium acetate adjusted to p H 5.0）within 4 min.The quantification was performed by multiple reaction monitoring with the transitions of m/z 336.0-320.1 for berberine,m/z 352.0-336.1for palmatine,m/z 338.0-322.1 for jatrorrhizine,m/z 336.0-320.1 for epiberberine,m/z 320.0-292.1 for coptisine and m/z 356.4-192.1 for IS.Results：The lower limit of quantification for five protoberberine-type alkaloids was 0.05 ng/m L.Linearity,accuracy,precision,stability and matrix effect of five analytes were all satisfactory.Five protoberberinetype alkaloids were quickly distributed in the brain.Moreover,significant differences in the principal pharmacokinetic parameters such as AUC andthe analytes were observed between two groups.Conclusion：The LC-MS/MS method combinated with microdialysis is useful in the brain pharmacokinetic study of five protoberberine-type alkaloids.The results indicated that the rates of analytes absorption in insomnic rats were significantly higher than those in normal rats.Besides,the protoberberine-type alkaloids could bring a direct effect on the neuron in the hippocampus.