Monitoring chemical dynamics in vivo using capillary ultrafiltration and microdialysis probes
Abstract
The objective of my research has been to develop an understanding of continuous in vivo sampling probes for small molecules in awake, freely-moving animals. Capillary ultrafiltration and microdialysis probes are two such devices that were investigated. Capillary ultrafiltration and microdialysis probes are novel tools that can provide continuous in vivo monitoring of small molecules with several advantages over traditional methods. These advantages include providing "clean" samples that are free of enzymes and cell material, continuous unattended observation, and the use of awake, freely-moving animals without sacrifice. Microdialysis and capillary ultrafiltration probes are complementary techniques utilizing hydrophilic membrane fibers in the range of 100-300 $\mu$m in diameter. Capillary ultrafiltration probes utilize a negative pressure across the membrane capillary, whereby small molecules and extracellular fluid (intercellular fluid) are actively "pulled" across the membrane and collected. Microdialysis probes function by the diffusion of molecules across a membrane capillary into a perfusion fluid that is pumped through the membrane fiber. Microdialysis probes can be constructed in several formats and typically have membranes from 1 mm to 60 mm in length. Each of these two techniques has unique advantages, and limitations. The quantitative aspects and practical considerations of both probe types were studied. The monitoring of therapeutic drug disposition and the determination of pharmacokinetics was explored. The pharmacokinetics of acetaminophen and theophylline were determined in awake rats using capillary ultrafiltration probes implanted in the subcutaneous tissue and in human saliva in situ. Drugs were quantitated using either capillary electrophoresis or liquid chromatography. The monitoring of ions in the intercellular space and a comparison to blood concentrations was conducted. The hyperinsulinemic dependent uptake of potassium from the intercellular space was observed using capillary ultrafiltration. The use of loop geometry microdialysis probes with increased membrane lengths were studied for the quantitative determination of pharmacokinetics in awake rats. Investigation of the co-administration of ethanol and acetaminophen on the pharmacokinetics of both drugs and the metabolites of acetaminophen was explored. The development of an alcohol oxidase enzyme reactor for the determination of ethanol in biological samples was pursued.
Degree
Ph.D.
Advisors
Kissinger, Purdue University.
Subject Area
Analytical chemistry|Pharmacology|Pharmacology
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