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Analytica Chimica Acta Oct 2009Methods and advances for monitoring neurotransmitters in vivo or for tissue analysis of neurotransmitters over the last five years are reviewed. The review is organized... (Review)
Review
Methods and advances for monitoring neurotransmitters in vivo or for tissue analysis of neurotransmitters over the last five years are reviewed. The review is organized primarily by neurotransmitter type. Transmitter and related compounds may be monitored by either in vivo sampling coupled to analytical methods or implanted sensors. Sampling is primarily performed using microdialysis, but low-flow push-pull perfusion may offer advantages of spatial resolution while minimizing the tissue disruption associated with higher flow rates. Analytical techniques coupled to these sampling methods include liquid chromatography, capillary electrophoresis, enzyme assays, sensors, and mass spectrometry. Methods for the detection of amino acid, monoamine, neuropeptide, acetylcholine, nucleoside, and soluble gas neurotransmitters have been developed and improved upon. Advances in the speed and sensitivity of these methods have enabled improvements in temporal resolution and increased the number of compounds detectable. Similar advances have enabled improved detection at tissue samples, with a substantial emphasis on single cell and other small samples. Sensors provide excellent temporal and spatial resolution for in vivo monitoring. Advances in application to catecholamines, indoleamines, and amino acids have been prominent. Improvements in stability, sensitivity, and selectivity of the sensors have been of paramount interest.
Topics: Biosensing Techniques; Chromatography, High Pressure Liquid; Electrophoresis, Capillary; Enzyme Assays; Mass Spectrometry; Microdialysis; Neurotransmitter Agents
PubMed: 19800472
DOI: 10.1016/j.aca.2009.08.038 -
Pharmacology, Biochemistry, and Behavior Aug 2008Central nervous system (CNS) insults elevate endogenous toxins and alter levels of indicators of metabolic disorder. These contribute to neurotrauma, neurodegenerative... (Review)
Review
Central nervous system (CNS) insults elevate endogenous toxins and alter levels of indicators of metabolic disorder. These contribute to neurotrauma, neurodegenerative diseases and chronic pain and are possible targets for pharmaceutical treatment. Microdialysis samples substances in the extracellular space for chemical analysis. It has demonstrated that toxic levels of glutamate are released and that toxic levels of the reactive species O(2)(-), H(2)O(2), HO. NO and HOONO are generated upon CNS injury. Agent administration by microdialysis can also help elucidate mechanisms of damage and protection, and to identify targets for clinical application. Microdialysis sampling indicates that circuits descending from the brain to the spinal cord transmit and modulate pain signals by releasing neurotransmitter amines and amino acids. Efforts are under way to develop microdialysis into a technique for intensive care monitoring and predicting outcomes of brain insults. Finally, microdialysis sampling has demonstrated in vivo elevation of glial cell line-derived neurotrophic factor following grafting of primed fetal human neural stem cells into brain-injured rats, the first in vivo demonstration of the release of a neurotrophic factor by grafted stem cells. This increased release correlated with significantly improved spatial learning and memory.
Topics: Animals; Brain Injuries; Calibration; Central Nervous System Diseases; Glutamic Acid; Hydroxyl Radical; Microdialysis; Neurons; Pain; Reactive Oxygen Species; Spinal Cord Injuries; Zinc
PubMed: 18436292
DOI: 10.1016/j.pbb.2008.03.001 -
Journal of Diabetes Science and... Sep 2011The aim was to evaluate intravascular microdialysis as a method for measuring blood glucose and lactate in a clinical setting during and after cardiac surgery.
BACKGROUND
The aim was to evaluate intravascular microdialysis as a method for measuring blood glucose and lactate in a clinical setting during and after cardiac surgery.
METHODS
Ten patients undergoing cardiac surgery were included. A microdialysis catheter was percutaneously placed in the superior vena cava or right atrium. Glucose and lactate values measured by the microdialysis technique were analyzed and compared with reference methods, i.e., arterial and venous blood gas values, once every hour up to 24 hours postoperatively. Laboratory plasma glucose was additionally analyzed every 4 hours for reference value.
RESULTS
Mean absolute differences were low between microdialysis and reference methods for both glucose and lactate values. All microdialysis glucose values were in the clinically acceptable zone of error grid analysis when compared with plasma glucose values. Accuracy of glucose values was 92% according to International Organization for Standardization criteria.
CONCLUSIONS
Intravascular microdialysis is a novel and promising technique for real-time and accurate measurement of glucose and lactate during and after open heart surgery. Development of sensor technology may allow for continuous measurement of blood glucose and lactate using intravascular microdialysis.
Topics: Aged; Cardiac Surgical Procedures; Female; Glucose; Humans; Lactic Acid; Male; Microdialysis; Middle Aged; Postoperative Period
PubMed: 22027302
DOI: 10.1177/193229681100500510 -
Analytical and Bioanalytical Chemistry Sep 2020Microchip electrophoresis with amperometric detection (ME-EC) is a useful tool for the determination of redox active compounds in complex biological samples. In this... (Review)
Review
Microchip electrophoresis with amperometric detection (ME-EC) is a useful tool for the determination of redox active compounds in complex biological samples. In this review, a brief background on the principles of ME-EC is provided, including substrate types, electrode materials, and electrode configurations. Several different detection approaches are described, including dual-channel systems for dual-electrode detection and electrochemistry coupled with fluorescence and chemiluminescence. The application of ME-EC to the determination of catecholamines, adenosine and its metabolites, and reactive nitrogen and oxygen species in microdialysis samples and cell lysates is also detailed. Lastly, approaches for coupling of ME-EC with microdialysis sampling to create separation-based sensors that can be used for near real-time monitoring of drug metabolism and neurotransmitters in freely roaming animals are provided. Graphical abstract.
Topics: Animals; Electrochemical Techniques; Electrodes; Electrophoresis, Microchip; Equipment Design; Mice; Microdialysis; Sheep
PubMed: 32347360
DOI: 10.1007/s00216-020-02647-z -
Analytical and Bioanalytical Chemistry Aug 2017Cerebral microdialysis is a sampling technique which offers much potential for understanding inflammatory pathophysiology following traumatic brain injury (TBI). At...
Cerebral microdialysis is a sampling technique which offers much potential for understanding inflammatory pathophysiology following traumatic brain injury (TBI). At present, the recovery of cytokines via microdialysis in clinical studies is not straightforward primarily due to their size, steric properties and low concentrations. Heparin and heparin-coated microspheres have previously shown promise as cytokine-binding agents for enhanced microdialysis sampling in animal models (Duo and Stenken in Anal Bioanal Chem 399(2):773-82, 2011; Anal Bioanal Chem 399(2):783-93, 2011). However, there are several factors limiting application for microdialysis in patients. The aim of this study was to produce heparin-coated gold nanoparticles as cytokine capture agents for enhanced microdialysis sampling, potentially applicable to a clinical setting. Gold nanoparticles (AuNP) were chemically conjugated to heparin via a bifunctional polyethylene glycol (PEG) linker. The heparin-AuNP (AuNP-Hep) were characterised, demonstrating the successful addition of heparin to the gold surface. The performance of the AuNP-Hep during in vitro testing was compared both to current methodology (Helmy et al. in J Neurotrauma 26(4):549-61, 2009) and to the heparin-coated microspheres developed by Duo and Stenken (Anal Bioanal Chem 399(2):773-82, 2011; Anal Bioanal Chem 399(2):783-93, 2011). The AuNP-Hep yielded a higher recovery of cytokines compared to current methodology and heparin-coated microspheres, during in vitro testing designed to mimic the human environment and the intensive care unit. In this study, AuNP-Hep were developed for enhanced microdialysis sampling of cytokines, potentially applicable in a clinical setting. Based on the success of the AuNP-Hep in vitro, the proposed method offers an alternative to the use of current protocols that rely on a blood product (albumin) for microdialysis sampling of cytokines in patients.
Topics: Cytokines; Gold; Heparin; Humans; In Vitro Techniques; Metal Nanoparticles; Microdialysis; Microscopy, Electron, Transmission
PubMed: 28664332
DOI: 10.1007/s00216-017-0447-y -
Pharmaceutical Research Jan 2008This paper reviews some current methods for the in vivo assessment of local cutaneous bioavailability in humans after topical drug application. After an introduction... (Review)
Review
This paper reviews some current methods for the in vivo assessment of local cutaneous bioavailability in humans after topical drug application. After an introduction discussing the importance of local drug bioavailability assessment and the limitations of model-based predictions, the focus turns to the relevance of experimental studies. The available techniques are then reviewed in detail, with particular emphasis on the tape stripping and microdialysis methodologies. Other less developed techniques, including the skin biopsy, suction blister, follicle removal and confocal Raman spectroscopy techniques are also described.
Topics: Administration, Topical; Algorithms; Biological Availability; Humans; Microdialysis; Microscopy, Confocal; Pharmaceutical Preparations; Pharmacokinetics; Skin; Skin Absorption
PubMed: 17985216
DOI: 10.1007/s11095-007-9429-7 -
Metabolic Brain Disease Jun 2015The pathophysiology of traumatic brain (TBI) injury involves changes to glucose uptake into the brain and its subsequent metabolism. We review the methods used to study... (Review)
Review
The pathophysiology of traumatic brain (TBI) injury involves changes to glucose uptake into the brain and its subsequent metabolism. We review the methods used to study cerebral glucose metabolism with a focus on those used in clinical TBI studies. Arterio-venous measurements provide a global measure of glucose uptake into the brain. Microdialysis allows the in vivo sampling of brain extracellular fluid and is well suited to the longitudinal assessment of metabolism after TBI in the clinical setting. A recent novel development is the use of microdialysis to deliver glucose and other energy substrates labelled with carbon-13, which allows the metabolism of glucose and other substrates to be tracked. Positron emission tomography and magnetic resonance spectroscopy allow regional differences in metabolism to be assessed. We summarise the data published from these techniques and review their potential uses in the clinical setting.
Topics: Animals; Autoradiography; Brain Injuries; Energy Metabolism; Extracellular Fluid; Glucose; Humans; Magnetic Resonance Imaging; Microdialysis; Positron-Emission Tomography
PubMed: 25413449
DOI: 10.1007/s11011-014-9628-y -
British Journal of Anaesthesia Mar 2005After aneurysmal subarachnoid haemorrhage (SAH), the clinical outcome depends upon the primary haemorrhage and a number of secondary insults in the acute... (Review)
Review
After aneurysmal subarachnoid haemorrhage (SAH), the clinical outcome depends upon the primary haemorrhage and a number of secondary insults in the acute post-haemorrhagic period. Some secondary insults are potentially preventable but prevention requires prompt recognition of cerebral or systemic complications. Currently, several neuro-monitoring techniques are available; this review describes the most frequently used techniques and discusses indications for their use, and their value in diagnosis and prognosis. None of the techniques, when considered in isolation, has proved sufficient after SAH. Furthermore, the use of multi-modality monitoring is hampered by a lack of clinical studies that identify combinations of specific techniques in terms of clinical information and reliability. However, ischaemia at the tissue level can be detected by intracerebral microdialysis technique. Used together with the conventional monitoring systems, for example intracranial pressure measurements, transcranial Doppler ultrasound and modern neuro-imaging, direct assessment of biochemical markers by intracerebral microdialysis is promising in the advancement of neurointensive care of patients with SAH. A successfully implemented monitoring system provides answers but it also raises valuable new questions challenging our current understanding of the brain injury after SAH.
Topics: Cerebrovascular Circulation; Critical Care; Humans; Intracranial Aneurysm; Intracranial Pressure; Microdialysis; Monitoring, Physiologic; Oximetry; Subarachnoid Hemorrhage; Ultrasonography, Doppler, Transcranial
PubMed: 15516355
DOI: 10.1093/bja/aei004 -
European Journal of Pharmaceutical... Sep 2023Many novel small drug molecules are poorly water-soluble and thus, enabling drug formulations may be required to ensure sufficient absorption upon oral administration....
Combining in vitro dissolution/permeation with microdialysis sampling: Capabilities and limitations for biopharmaceutical assessments of supersaturating drug formulations.
Many novel small drug molecules are poorly water-soluble and thus, enabling drug formulations may be required to ensure sufficient absorption upon oral administration. Biopharmaceutical assessment and absorption prediction of enabling formulations, however, remains challenging. Combined in vitro dissolution/permeation (D/P) assays have gained increasing interest since they may provide a more realistic formulation ranking based on the drug permeation profiles from different formulations as compared to conventional dissolution, which captures both readily permeable and not readily permeable fractions of "dissolved" drug. Moreover, the combined in vitro D/P assays allow to better predict intestinal supersaturation and precipitation processes as compared to simple dissolution setups due to the effect of an absorptive sink. Microdialysis on the other hand has proven useful to determine molecularly dissolved drug in colloidal dispersions, thus allowing for a deeper mechanistic insight into the mechanism of drug release from supersaturating formulations. Here, microdialysis sampling from the donor compartment was used in combination with the dissolution/permeation (D/P) tool PermeaLoop™ to study commercial supersaturating drug formulations of the poorly soluble and weakly basic drug Posaconazole (PCZ). An amorphous solid dispersion (ASD)-based tablet, as well as a crystalline suspension in acidified and neutral dilution medium, respectively, were tested. Microdialysis sampling allowed for differentiation between molecularly dissolved and micellar drug concentration, as expected, but, surprisingly, it was found that the presence of the microdialysis probe affected the precipitation behavior of a crystalline suspension within the two-stage D/P setup, simulating the oral administration of the acidified PCZ (Noxafil®) suspension: the extent and duration of supersaturation in the donor decreased significantly, which also affected permeation. Similarly, for the ASD-based tablet, a less pronounced supersaturation was observed during the first 120 min of the experiment. Hence, in this case, the formulation ranking and the prediction of intestinal supersaturation in the in vitro D/P assay became less predictive as compared to a conventional PermeaLoop™ study without microdialysis sampling. It was concluded that valuable mechanistic insights into the molecularly dissolved drug profiles over time can be obtained by microdialysis. However, since the presence of the probe may affect the degree of supersaturation and precipitation, a conventional D/P assay (without microdialysis sampling) is preferred for formulation ranking of supersaturating drug formulations.
Topics: Solubility; Chemistry, Pharmaceutical; Drug Compounding; Biological Products; Microdialysis; Drug Liberation; Tablets
PubMed: 37480963
DOI: 10.1016/j.ejps.2023.106533 -
Postepy Higieny I Medycyny... Jun 2007Homeostasis of human and animal organisms and its disturbance are explored mainly by evaluating metabolic substrates and metabolite concentrations and their changes... (Review)
Review
Homeostasis of human and animal organisms and its disturbance are explored mainly by evaluating metabolic substrates and metabolite concentrations and their changes under different clinical conditions. This review describes a method of tissue biochemistry monitoring by analysis of extracellular fluid dialysate. Microdialysis not only provides information about the general disturbances of the body, but allows insight into the local metabolism of tissues and organs. It can be applied both in experimental conditions (e.g. animal neurophysiology) and in clinical practice (episodes of brain ischemia, glycemic disturbances, pharmacodynamic studies). The technique of microdialysis is relatively simple and is based on microdialysis probe implantation into the studied organ or tissue, followed by measurement of the obtained samples of extracellular fluid dialysate. During the last twenty years, microdialysis probes have been inserted into different part of the living organism: brain, skeletal muscles, subcutaneous adipose tissue, transplanted tissues (myocutaneous flap) and organs (liver), tendons, skin, breast gland, lungs, heart muscle, intestines, and body cavities. The possibility of frequent sampling (every 20-60 minutes) and measuring the concentrations of glucose, glycerol, lactates, and pyruvates with a bedside analyzer in an average time of 2-3 minutes is considered a great advantage of this method. Microdialysis gives many opportunities for a better understanding of how living organisms are functioning, but it requires cautious application and validation in clinical observations in order to make standards and recommendations (diseases and clinical conditions, substances for monitoring, referenced values and trends) for its common medical usage.
Topics: Adipose Tissue; Animals; Brain; Humans; Microdialysis; Muscle, Skeletal; Pharmacology; Skin; Tissue Distribution
PubMed: 17572658
DOI: No ID Found