Mikrodializ

Mikrodializ is a sampling technique used to measure concentrations of soluble molecules in the extracellular fluid of living tissue by diffusion across a semipermeable membrane. A small dialysis probe is implanted into the target tissue. An isotonic perfusate is pumped through the probe at a slow, constant flow. Molecules from the surrounding interstitial fluid diffuse across the membrane into the perfusate and are collected as dialysate for analysis.

Microdialysis enables continuous, in vivo sampling with higher temporal resolution than many traditional methods. This approach is widely used in neuroscience, pharmacology, and metabolism research to monitor dynamic changes in chemical signaling and metabolic activity within intact tissue.

Typical probes use a concentric design with a semi-permeable membrane, and the membrane length is often in the sub-millimeter to few-millimeter range. The membrane’s molecular weight cutoff and the perfusate flow rate influence what substances can be sampled and how efficiently they are recovered. Flow rates commonly range from about 0.2 to 2 microliters per minute.

Dialysate is analyzed with various laboratory techniques, including high-performance liquid chromatography, liquid chromatography–mass spectrometry, and capillary electrophoresis, to quantify target analytes such as neurotransmitters, metabolites, and drugs. Recovery, the fraction of the true extracellular concentration that appears in the dialysate, depends on membrane properties, flow rate, and tissue characteristics; calibration methods such as retrodialysis aid interpretation.

Applications span neuroscience (for example, monitoring dopamine, glutamate, and GABA), metabolism (glucose, lactate), and pharmacokinetics (tissue drug concentrations). Limitations include relatively low temporal resolution, indirect concentration measurements, potential tissue damage, and the need for careful calibration, especially for larger molecules. In clinical settings, mikrodializ is performed under approved protocols to monitor tissue chemistry in patients or to study drug distribution.