Development of an integrated microperfusion-EEG electrode for unbiased multimodal sampling of brain interstitial fluid and concurrent neural activity

Abstract

Objective. To modify off-the-shelf components to build a device for collecting EEG from macroelectrodes surrounded by large fluid access ports sampled by an integrated microperfusion system in order to establish a method for sampling brain interstitial fluid at the site of seizure activity with no bias for molecular size. Approach. Twenty-four 560 µm diameter holes were ablated through the sheath surrounding one platinum-iridium macroelectrode of a standard Spencer depth electrode using a femtosecond UV laser. A syringe pump was converted to push-pull configuration and connected to the fluidics catheter of a commercially available microdialysis system. The fluidics were inserted into the lumen of the modified Spencer electrode with the microdialysis membrane removed, converting the system to open flow microperfusion. Electrical performance and analyte recovery were measured and parameters were systematically altered to improve performance. An optimized device was tested in the pig brain and unbiased quantitative mass spectrometry was used to characterize the perfusate collected from the peri-electrode brain in response to stimulation. Main Results. Optimized parameters resulted in >70% recovery of 70 kDa dextran from a tissue analog. The optimized device was implanted in the cortex of a pig and perfusate was collected during four 60-minute epochs. Following a baseline epoch, the macroelectrode surrounded by microperfusion ports was stimulated at 2 Hz (0.7 mA, 200 µs pulse width). Following a post-stimulation epoch, the cortex near the electrode was stimulated with benzylpenicillin to induce epileptiform activity. Proteomic analysis of the perfusates revealed a unique inflammatory signature induced by electrical stimulation. This signature was not detected in bulk tissue interstitial fluid. Significance. A modified dual-sensing electrode that permits coincident detection of EEG and interstitial fluid at the site of epileptiform neural activity may reveal novel pathogenic mechanisms and therapeutic targets that are otherwise undetectable at the bulk tissue level.

Advances in computational and translational approaches for malignant glioma

“…Ongoing clinical trials (NCT04692337, NCT04047264) aim to utilize a similar paradigm but with the incorporation of real-time, in situ and subsequent rapid assessment of potential therapeutic biomarkers and metabolomics. Advances in microelectrode and catheter technology including the development of lower profile instruments as well as those that can simultaneously sample brain interstitial fluid and neural activity hold promise for a more integrated, real-time assessment of molecular- and network-level changes in gliomas ( Rajani et al, 2021 ; Stangler et al, 2023 ). Stangler et al demonstrate that an integrated microperfusion-EEG electrode is able to detect epileptiform activity as well as sample interstitial fluid in a pig model with potential future implications of studying glioma-neuronal integration and functional reorganization in situ ( Stangler et al, 2023 ).…”