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Microfabrication and in Vivo Performance of a Microdialysis Probe with Embedded Membrane.

ABSTRACT: Microdialysis sampling is an essential tool for in vivo neurochemical monitoring. Conventional dialysis probes are over 220 ?m in diameter and have limited flexibility in design because they are made by assembly using preformed membranes. The probe size constrains spatial resolution and governs the amount of tissue damaged caused by probe insertion. To overcome these limitations, we have developed a method to microfabricate probes in Si that are 45 ?m thick × 180 ?m wide. The probes contain a buried, U-shaped channel that is 30 ?m deep × 60 ?m wide and terminates in ports for external connection. A 4 mm length of the probe is covered with a 5 ?m thick nanoporous membrane. The membrane was microfabricated by deep reactive ion etching through a porous aluminum oxide layer. The microfabricated probe has cross-sectional area that is 79% less than that of the smallest conventional microdialysis probes. The probes yield 2-20% relative recovery at 100 nL/min perfusion rate for a variety of small molecules. The probe was successfully tested in vivo by sampling from the striatum of live rats. Fractions were collected at 20 min intervals (2 ?L) before and after an intraperitoneal injection of 5 mg/kg amphetamine. Analysis of fractions by liquid chromatography-mass spectrometry revealed reliable detection of 14 neurochemicals, including dopamine and acetylcholine, at basal conditions. Amphetamine evoked a 43-fold rise in dopamine, a result nearly identical to a conventional dialysis probe in the same animal. The microfabricated probes have potential for sampling with higher spatial resolution and less tissue disruption than conventional probes. It may also be possible to add functionality to the probes by integrating other components, such as electrodes, optics, and additional channels.

SUBMITTER: Lee WH

PROVIDER: S-EPMC5111822 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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Microfabrication and in Vivo Performance of a Microdialysis Probe with Embedded Membrane.

Lee Woong Hee WH Ngernsutivorakul Thitaphat T Mabrouk Omar S OS Wong Jenny-Marie T JM Dugan Colleen E CE Pappas Samuel S SS Yoon Hyeun Joong HJ Kennedy Robert T RT

Analytical chemistry 20160104 2

Microdialysis sampling is an essential tool for in vivo neurochemical monitoring. Conventional dialysis probes are over 220 μm in diameter and have limited flexibility in design because they are made by assembly using preformed membranes. The probe size constrains spatial resolution and governs the amount of tissue damaged caused by probe insertion. To overcome these limitations, we have developed a method to microfabricate probes in Si that are 45 μm thick × 180 μm wide. The probes contain a bu ...[more]

PMID: 26727611

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Project description:BackgroundThere is no uniform definition for cerebral microdialysis (CMD) probe location with respect to focal brain lesions, and the impact of CMD-probe location on measured molecule concentrations is unclear.MethodsWe retrospectively analyzed data of 51 consecutive subarachnoid hemorrhage patients with CMD-monitoring between 2010 and 2016 included in a prospective observational cohort study. Microdialysis probe location was assessed on all brain computed tomography (CT) scans performed during CMD-monitoring and defined as perilesional in the presence of a focal hypodense or hyperdense lesion within a 1-cm radius of the gold tip of the CMD-probe, or otherwise as normal-appearing brain tissue.ResultsProbe location was detected in normal-appearing brain tissue on 53/143 (37%) and in perilesional location on 90/143 (63%) CT scans. In the perilesional area, CMD-glucose levels were lower (p = 0.003), whereas CMD-lactate (p = 0.002), CMD-lactate-to-pyruvate-ratio (LPR; p < 0.001), CMD-glutamate (p = 0.002), and CMD-glycerol levels (p < 0.001) were higher. Neuroglucopenia (CMD-glucose < 0.7 mmol/l, p = 0.002), metabolic distress (p = 0.002), and mitochondrial dysfunction (p = 0.005) were more common in perilesional compared to normal-appearing brain tissue. Development of new lesions in the proximity of the CMD-probe (n = 13) was associated with a decrease in CMD-glucose levels, evidence of neuroglucopenia, metabolic distress, as well as increasing CMD-glutamate and CMD-glycerol levels. Neuroglucopenia was associated with poor outcome independent of probe location, whereas elevated CMD-lactate, CMD-LPR, CMD-glutamate, and CMD-glycerol levels were only predictive of poor outcome in normal-appearing brain tissue.ConclusionsFocal brain lesions significantly impact on concentrations of brain metabolites assessed by CMD. With the exception of CMD-glucose, the prognostic value of CMD-derived parameters seems to be higher when assessed in normal-appearing brain tissue. CMD was sensitive to detect the development of new focal lesions in vicinity to the neuromonitoring probe. Probe location should be described in the research reporting brain metabolic changes measured by CMD and integrated in statistical models.

Dataset Information

Microfabrication and in Vivo Performance of a Microdialysis Probe with Embedded Membrane.

Publications

Microfabrication and in Vivo Performance of a Microdialysis Probe with Embedded Membrane.

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