Microdialysis & Ultrafiltration

Historically, most information about the distribution and concentration of endogenous and exogenous compounds has been based on blood sampling or homogenized tissue. In the case of endogenous compounds, sampling plasma or homogenized tissue only provides data on concentrations and provides little or no insight into the physiology of temporal release patterns or release stimuli. While blood sampling can provide multiple serial samples from a single animal, it sums analyte concentrations from all tissues and offers no anatomical specificity. While sampling tissue does provide anatomical specificity, it usually permits only one sample per tissue/animal and thus can dramatically increase the number of animals required in a study.

In Vivo Microdialysis and Ultrafiltration Sampling address these limitations and are two of the very few sampling techniques that allows for direct sampling in the interstitial fluid, allowing investigators to measure free analyte concentrations along with temporal and spatial release and concentration patterns. While both are semi-permeable membrane based sampling techniques, the applications and features of these two techniques differ.


Most often, Microdialysis (MD) sampling has been used for preclinical tracking of brain neurotransmitter release after administration of CNS treatments or compounds. However, MD sampling techniques are also used to sample from a variety of tissues and species. Unlike blood or tissue sampling, by dialyzing across a semi-permeable membrane, microdialysis does not add or remove any fluids, only molecules. As a result, many serial samples can be monitored -in many cases from awake, freely moving animals. This can help to dramatically reduce and refine your animal usage. Microdialysis allows sampling times of minutes to hours. Contact for more information on the power and features that microdialysis sampling provides you.


Like Microdialysis, In Vivo Ultrafiltration (UF) also relies on the use of an implanted semi-permeable membrane. However, when you are trying to determine the actual concentration of analyte in the tissue, as opposed to relative changes, microdialysis methods may require that you perform additional experiments and extrapolate to determine that figure. In contrast, in vivo ultrafiltration does not simply recover a percentage of the analyte. Instead, it extracts the actual extracellular fluid and filters it to exclude high molecular weight compounds such as proteins. The concentration of an analyte in the ultra-filtrate represents the concentration of that analyte in the adjacent extracellular space. Ultrafiltration may allow sampling times ranging from hours to weeks. Click here for more information on the power and features that in vivo ultrafiltration sampling provides you.

Getting Started

BASi offers everything you need to start microdialysis or ultrafiltration membrane based sampling. If you are just getting started, BASi offers flexible microdialysis packages to help ensure that you have the items you need to be successful. If you know you want a complete microdialysis package, or you want to learn more about what items you need to perform microdialysis, contact BASi. You can also click the following links for information on in vivo ultrafiltration probes or ultrafiltration accessories.

If you don't see what you need here, you want technical support, or you would like to discuss your specific needs, call or email.