Exploring Tissue Chemistry
CMA Microdialysis ("CMA”) is a Swedish medical device and research company founded in 1984 as a spin-off from the Karolinska Institute. Unique and market leading solutions are developed, produced and sold to researchers to enable optimized and accelerated drug development. CMA’s complete lines of instruments and consumables are used globally by universities and pharmaceutical companies as unique tools for pre-clinical research.
In basic research Microdialysis is an indispensible tool for drug discovery. CMA’s solutions are used across the globe by drug developers and researchers to achieve fast and efficient drug discovery. CMA´s vision is: To substantially shorten the time-to-market of drug and research projects by offering a complete and leading portfolio of Microdialysis products.
When using the 100 kDa cut-off membrane there is a risk for ultra filtration: Perfusion fluid passes into the tissue (=ultra filtration); less fluid remains in the catheter i.e. the flow of perfusion fluid in the catheter is lowered. Lower flow rates means higher concentration (recovery) as each µL of perfusate has more time to take up molecules diffusing over the membrane. You need push-pull when you are losing to much of the perfusion fluid to the surrounding tissue = too much ultrafiltration (UL). This normally happens when you are using a high cut-off membrane.
When you perfuse fluid trough the probe you create a positive pressure inside. If your membrane has a high cut-off, the fluid will just float over the membrane and into the tissue = no sample to collect. The UL is also affected by the osmotic force in the tissue. High local capillary blood flow = higher osmotic force = more fluid from the probe is removed per minute. This means that the UL is not the same in all tissues. e.g. you have more UL in muscle tissue then adipose tissue.
To use push pull will balance up the pressure inside the membrane. In order to balance up the osmotic pressure you can add albumin or dextran to the perfusion fluid. But in general practice this is not done so much because of problems with air bubbles. When you use 100 kDa membrane push-pull is normally not needed. But with our new Ultra High Probes 1.000 kDa membrane you need a push-pull system.