A minimally invasive method for sampling the interstitial fluid in human brain tissue is cerebral microdialysis (CMD). CMD enables sampling of macromolecules like proteins and peptides as well as monitoring the metabolic state of tissue. It has been demonstrated in-vitro that protein adsorption to the CMD membrane can hinder protein recovery; however, protein adsorption to CMD membranes after implantation in human brain tissue has not been studied. In this article, we compare the protein-adsorbed pattern on CMD membranes to that of microdialysate and cerebrospinal fluid (CSF).

We took CMD membranes from three patients who had undergone surgical treatment for intracerebral haemorrhage (ICH) and used two-dimensional gel electrophoresis (2-DE) in conjunction with nano-liquid mass spectrometry to examine protein adsorption to the membranes. Three compartments—the CMD membrane, the microdialysate, and the ventricular CSF collected at the moment of CMD removal—had their proteome profiles compared.

There are a number of technical considerations when employing CMD to sample macromolecules from interstitial fluid. In the CMD procedure, a thin dialysis catheter made of a semipermeable membrane is inserted into the brain tissue. Fluid is injected into the catheter, collected, and then examined. The fluid that was gathered, known as the microdialysate, is an image of the interstitial fluid. However, because it depends on a number of variables, the relative recovery of molecules in the microdialysate is never a perfect representation of their true tissue content. These variables include tissue temperature, pH, and tortuosity; perfusate flow rate and composition; protein molecular weight, three-dimensional structure, and hydrophobicity.

On the CMD membrane, distinct proteins were discovered that were not present in the dialysate or the CSF. BRICK1, which is necessary for cell division and transformation as well as directional migration, was one of them. Its downregulation is linked to invasive growth in a variety of tumour cell types.