Microdialysis (MD) is a minimally invasive in-vivo technique that is used for continuous sampling of chemical changes in tissues. MD can be used in virtually any tissue including skin. The MD probe is designed to mimic the function of capillaries that allow the transport of substances to and from the tissue of interest. In most cases the purpose of MD is to sample the tissue environment for clinical or research applications.

Sampling with MD

The MD probe consists of two chambers – an inlet tube and an outlet tube. After implanting the probe in the tissue (muscle in the diagram) a selected perfusion fluid (dependent on the substance sought) is slowly infused through the inlet tubing and transported down to the probe tip into the muscle. The tip of the probe is semipermeable, i.e. includes small side holes so that substances can diffuse in and out. This will be determined by the concentration of a particular substance in the extracelluar space, amongst other factors. The perfusion fluid is continuously transported up to the outlet tubing where it can be collected for analysis. Usually the substance is stored in a freezer until it is ready to be analyzed.