Microdialysis is a unique technique to monitor the chemistry of the extracellular space in living tissue. In basic research it is primarily used for In Vivo determinations of endogenous compound changes, drug delivery, PK/PD, bioavailability and bioequivalence.
The Microdialysis probe
The Microdialysis probe designed to mimic a blood capillary, has a semi-permeable membrane that, when perfused with a physiological salt solution, allows an exchange of compounds from an area of high concentration to an area of low concentration. A representative proportion of molecules from the extracellular fluid is then carried to the probe outlet for collection and analysis.
With a various range of Microdialysis membranes, it is possible to sample molecules in size ranging from a few hundred Daltons up to about 30,000 Daltons, making it feasible to monitor neuro-transmission, amino acids, energy metabolites, markers of inflammation, pain, and disease biomarkers, as well as available drug levels in target tissues.
Basic Research Applications
For more than thirty years, Microdialysis has been used to study brain neurophysiology and the release of neurotransmitters, monoamines and metabolites, amino acids and other small endogenous compounds. Now, with the introduction of several new Microdialysis probes for use in the peripheral organs, Microdialysis is seeing widespread use in sampling molecules in tissues such as muscle, liver and adipose tissue, as well as in the spinal cord, synovial fluid, vitreous humour and blood, to assess the delivery and distribution of parent drug and metabolites and their effects on endogenous compounds.
Today, two of the hottest areas into which Microdialysis probes are placed are tumor and skin. In these areas, as in the others mentioned above, Microdialysis is used to collect free available drugs and soluble endogenous factors, including cytokines, simultaneously in real time in vivo, to assess penetration. Also, drugs can be delivered intratumorally or into the dermis through the probe to assess effects on collectable biomarkers.
Since the exchange of molecules through the dialysis membrane is in both directions, a Microdialysis probe placed in target tissue, can be used to continuously:
- sample unbound drug and/or active metabolites as they arrive to the tissue following systemic administration;
- deliver drugs locally into an organ or tissue through the probe, and simultaneously collect endogenous target compounds to determine pharmacological effect, and;
- assess controlled release of drugs from encapsulation following administration within specific sites
In summary, Microdialysis is a valuable tool for in vivo evaluation studies on drug delivery, drug metabolism, PK/PD, bioavailability, bioequivalence and pharmacological efficacy. It is the only technique that gives simultaneous in vivo temporal information on unbound drug and metabolic levels as well as endogenous compounds in target tissues.
CMA offers a complete and leading suite of Microdialysis solutions that meets the needs of advanced research. All products are produced under high quality standards and in a clean environment in Sweden.
For more information about CMA's basic research solutions, please contact us or your local distributor.