Mikrodialyse

Mikrodialyse is a minimally invasive sampling technique used to measure the chemical composition of the extracellular fluid in living tissues. A microdialysis probe with a semipermeable membrane at its tip is inserted into the target tissue. A physiological perfusate, usually isotonic saline, is pumped through the membrane at a slow flow rate. Molecules in the tissue diffuse across the membrane into the perfusate and form the dialysate, which is collected over time for laboratory analysis. The method enables in vivo monitoring of soluble compounds such as neurotransmitters, metabolites, and drugs.

Principle and recovery. The amount of an analyte appearing in the dialysate depends on its diffusion across the membrane and on the probe’s recovery, which is influenced by factors including membrane molecular weight cut-off, surface area, perfusion flow rate, tissue characteristics, and temperature. Lower flow rates and larger membrane areas generally increase recovery but reduce temporal resolution. Calibration methods, such as zero-net flux and retrodialysis, are used to estimate in vivo recovery and to correct measured concentrations.

Applications. Mikrodialyse is widely used in neuroscience to study extracellular neurotransmitters in brain tissue, as well as in pharmacology and toxicology to characterize tissue distribution and metabolism of drugs. It is also employed in clinical research and patient care to monitor metabolites, glucose, lactate, and other substances in tissues during surgery or in critical care settings.

Advantages and limitations. The technique provides continuous, real-time sampling with high chemical specificity and minimal tissue disruption. Limitations include invasiveness, potential tissue damage, and the need for careful calibration to interpret dialysate concentrations as accurate reflections of interstitial levels.