Refined Microdialysis Method for Protein Biomarker Sampling in Acute Brain Injury in the Neurointensive Care Setting

Abstract

There is growing interest in cerebral microdialysis (MD) for sampling of protein biomarkers in neurointensive care (NIC) patients. Published data point to inherent problems with this methodology including protein interaction and biofouling leading to unstable catheter performance. This study tested the in vivo performance of a refined MD method including catheter surface modification, for protein biomarker sampling in a clinically relevant porcine brain injury model. Seven pigs of both sexes (10-12 weeks old; 22.2-27.3 kg) were included. Mean arterial blood pressure, heart rate, intracranial pressure (ICP) and cerebral perfusion pressure was recorded during the stepwise elevation of intracranial pressure by inflation of an epidural balloon catheter with saline (1 mL/20 min) until brain death. One naïve MD catheter and one surface modified with Pluronic F-127 (10 mm membrane, 100 kDa molecular weight cutoff MD catheter) were inserted into the right frontal cortex and perfused with mock CSF with 3% Dextran 500 at a flow rate of 1.0 μL/min and 20 min sample collection. Naïve catheters showed unstable fluid recovery, sensitive to ICP changes, which was significantly stabilized by surface modification. Three of seven naïve catheters failed to deliver a stable fluid recovery. MD levels of glucose, lactate, pyruvate, glutamate, glycerol and urea measured enzymatically showed an expected gradual ischemic and cellular distress response to the intervention without differences between naïve and surface modified catheters. The 17 most common proteins quantified by iTRAQ and nanoflow LC-MS/MS were used as biomarker models. These proteins showed a significantly more homogeneous response to the ICP intervention in surface modified compared to naïve MD catheters with improved extraction efficiency for most of the proteins. The refined MD method appears to improve the accuracy and precision of protein biomarker sampling in the NIC setting.

Monitoring the Neuroinflammatory Response Following Acute Brain Injury

“…The addition of colloids does not always improve the recovery of all cytokines; however, the relative recovery for TNF in 3.5% HAS has been shown to increase from 4.4 to 31.2%, a sevenfold increase (56). A 3% Dextran-500 solution shows equally encouraging results compared to crystalloid solutions (64), and has the capacity to improve extraction of even larger inflammatory mediators (65, 66) and has been empirically demonstrated to remain within a 100 kDa membrane catheter (67). In summary, the optimal recovery of cytokines within the MD samples is dependent upon perfusate supplemented with albumin or dextran, favoring an improved relative recovery and no net loss of fluid from the catheter.…”

A proteomic investigation of protein adsorption to cerebral microdialysis membranes in surgically treated intracerebral hemorrhage patients

“…This method, however, is not relevant when the aim is to sample all proteins present. Previous in vitro and preclinical studies show decreased protein adhesion to both CMD membrane and tubing following catheter modifications using triblock copolymers such as Pluronics 127® (6,33). However, to date these modifications have only been used in vitro or in preclinical studies.…”

“…Although protein adsorption to microdialysis membranes has been shown in vitro (6,8,11) and in invivo in skin(12) it has not been characterized on microdialysis membranes implanted in human brain tissue.…”

Surgically Treated Intracerebral Haemorrhage : Pathophysiology and Clinical Aspects

“…It is necessary to use a colloid in the perfusate when using high-molecular-weight cut-off membranes (100kDa), as the problem of ultrafiltration and fluid loss to the tissue otherwise becomes significant. Various Dextran molecules have been used as perfusate colloid (20,178,181,292) some of which have been shown to leak across the membrane into the tissue (178), where they can generate an undesirable inflammatory response (20). Recently, perfusion fluid consisting of artificial CSF with 3% added Dextran MW 500 has been certified for clinical use (M-Dialysis, Solna, Sweden) and our department has now switched to using this perfusate.…”

“…It is plausible that protein adsorption could be decreased by surface modification of microdialysis membranes and tubing, as has been done in preclinical studies showing improved recovery of for example cytokines (292,303). Until such modifications become available for clinical use, however, the results of Paper III emphasise the importance of analysing protein adsorption to the CMD-membrane for a more accurate characterisation of the proteome profile.…”