Microdialysis of cerebrospinal fluid in polyacrylamide gels: a suitable procedure prior to electrophoretic analysis

Most electrophoresis methods for separation of CSF proteins are generally preceded by some procedure of concentration and desalting of the specimen. Generally ultrafiltration techniques are used. The risk of losses, which may be unequal for different CSF proteins during such procedures, is to be stressed. On the other hand, desalting prior to isoelectric focusing (IEF) will minimize the curvature of the protein bands, and in isotachophoresis (ITP) faster separation and increased capacity with repeated sample application are made possible. Since some years microdialysis of samples has been performed by the authors and found to be a valuable procedure both prior to IEF and ITP. With respect to microheterogeneity and recovery, tested by IEF, immunonephelometry and radioiodinated proteins no losses were observed. Ion exchange of acrylamide in a mixed resin, and recrystallization of bisacrylamide, were found necessary to avoid absorption from very dilute protein solutions as CSF. Gel structure and performance were very dependent on polymerization conditions (time, temperature, initiator and accelerator concentrations).