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So to the science. Thanks to everybody that voted in the poll yesterday. This time over 70% of you said you had never heard of microdialysis. Wow.
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So let’s break it down. Microdialysis is an analytical technique used to sample the concentration of metabolites (glucose and lactate) and neurotransmitters (like dopamine and glutamate) in the extracellular (outside cell) space of the brain (and other parts of the body).
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Okay, so let’s go a step further. MICRO is at the length scale below a millimetre and above 1000 nanometres (the really small stuff). This length scale is crucial because microdialysis probes sample the extracellular space around cells which are on the microscale. 3/11
Now the definition of DIALYSIS is the separation of particles in a liquid based on differences in their abilities to pass through a membrane. You may have heard of renal dialysis, this is used when kidneys stop functioning properly. It is a very similar principle. 4/11
Okay, a quick analogy if you will. Think of not being tall enough to go on a rollercoaster ride, there was a minimum height requirement or cut-off point. With microdialysis, the membrane is the ride operator excluding particles based on their molecular weight.
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But that's not all… By incorporating these membranes into probes, you can sample the concentration of the environment, but you have to flow through a solution that is chemically similar to the environment around cells to obtain a measurable concentration.
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We call this a perfusate and pump it through an inlet, pass it over the membrane and create a concentration gradient with the outside environment. Diffusion of molecules will occur through the membrane. Molecules can then be sampled at the outlet, known as a dialysate. 7/11
Microdialysis has a bad name because it has a slow time resolution (hourly samples) and you normally have to monitor the dialysate (offline) using a High-Performance Liquid Chromatography (HPLC) machine. So many people can't be bothered BUT…
(no sponsorship btw
) 8/11
(no sponsorship btw
) 8/11
…the @boutelle_lab with brilliant scientists such as @hashemiLab @mrogers28 and many others helped develop rapid sampling microdialysis (rsMD) and subsequently what the group uses today, continuous online microdialysis (coMD).
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By combining the outlet of the probe to biosensors and/or ion-selective electrodes (ISEs), metabolites like glucose, or ions like potassium can be measured to see the chemical nature of SDs (see thread) and dynamic concentration changes to understand brain tissue health. 10/11 https://twitter.com/minoritystem/status/1285568979801706499
https://twitter.com/minoritystem/status/1285568979801706499
I use microdialysis as one of my techniques in making the next generation of probes for neuro-monitoring. One last thing. Do you know what electrocorticography is? #BlackInNeuro
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