Push-Pull Microdialysis

PsychoGenics offers push-pull microdialysis techniques for the collection of large molecules. This technique coupled with immunoassay detection permits measures of dynamic changes of peptides, proteins and other large molecules such as α-Synuclein, Tau, and cytokines. Microdialysis probes with large molecular weight cut offs (MWCO, 1000-3000 kDa) require special procedures for pressure equalization across the probe membrane to perform dialysis. We have successfully utilized several probes, AtmosLM (Eicom, San Diego,CA, USA), Brainlink (Brainlink, Groningen, NL) and CMA 12 Ultra HighCO (Harvard Apparatus, Holliston, MA USA) for the recovery of extracellular large molecules.

In the following example the ability to measure basal levels of alpha Synuclein and Tau over a 24 hr period using push pull techniques was demonstrated for a mouse Parkinson’s disease model Thy1-αSyn (Line 61) and Tauopathy model (Tg4510).

Figure 1: In vivo measurement of extracellular alpha-Synuclein levels in striatum of Thy1-αSyn (Line 61) mice during a 24 hours period using push pull microdialysis technology. One week after implantation of guide cannula, microdialysis probes with large molecular weight cut off (MW/CO, 3000kDa), were inserted via guide cannulas into the striatum of 7 week old male mice . The animal was then placed in a plastic observation cage and connected to a 2-channel swivel. The input of the dialysis probe was connected to a syringe pump, which delivered an artificial cerebrospinal fluid (CSF) with 0.15% HSA at a rate of 0.7 μl/min. The output from the swivel was attached to a peristaltic pump and a refrigerated fraction collector. Microdialysis samples were analyzed using Legend MaxTM human α-Synuclein ELISA kit (BioLegend) and α-Synuclein concentrations were calculated from standard curve and presented as percentage of baseline (amount at time 0).

Figure 2: In vivo measurement of extracellular total Tau (a) and phospho Thr181 (b) levels in striatum of rTg4510 mice during a 24 hour period using push pull technique. Microdialysis samples were collected as described above and were analyzed.using Milliplex MAP human Tau Magnetic Bead Panel (EMD Millipore). Concentrations were calculated from standard curves and presented as percentage of baseline (amount at time 0). Phospho Tau to Total Tau ratio is also presented (c).