Feasibility of implantable iron oxide nanoparticles in detecting brain activity-proof of concept in a rat model

Pierre-Olivier Champagne; Nathalie T Sanon; Lionel Carmant; Philippe Pouliot; Alain Bouthillier; Mohamad Sawan

doi:10.1016/j.eplepsyres.2021.106585

Feasibility of implantable iron oxide nanoparticles in detecting brain activity-proof of concept in a rat model

Epilepsy Res. 2021 May:172:106585. doi: 10.1016/j.eplepsyres.2021.106585. Epub 2021 Feb 17.

Authors

Pierre-Olivier Champagne¹, Nathalie T Sanon², Lionel Carmant², Philippe Pouliot³, Alain Bouthillier⁴, Mohamad Sawan⁵

Affiliations

¹ Polystim Neurotech Laboratory, Electrical Engineering Department, Polytechnique Montreal, Montreal, Canada; CHU Sainte-Justine Research Center, Montreal, Canada; Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, Canada. Electronic address: pierre-olivier.champagne@polymtl.ca.
² CHU Sainte-Justine Research Center, Montreal, Canada.
³ Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, Canada; Research Center, Montreal Heart Institute, Montreal, Canada.
⁴ Neurosurgery Department, University of Montreal Medical Center, Montreal, Canada.
⁵ Polystim Neurotech Laboratory, Electrical Engineering Department, Polytechnique Montreal, Montreal, Canada; Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, Canada.

PMID: 33636503
DOI: 10.1016/j.eplepsyres.2021.106585

Abstract

Background: Precise detection of zones of increased brain activity is a crucial aspect in the delineation of the cortical region responsible for epilepsy (epileptic focus). When possible, removal of this area can lead to improved control of epilepsy or even its cure. This study explores a new method of detection of electrical brain activity based on the surgical implantation of iron oxide superparamagnetic nanoparticles (SPIONs). By their magnetic nature, SPIONs tend to aggregate in the presence of magnetic fields. This study aims to demonstrate if brain's magnetic fields could change the aggregation status of SPIONs in a rat model.

Methods: Plastic containers (capsules) containing SPIONs in aqueous suspension were implanted over the cortex of either rats rendered epileptic or naive rats (sham). A model of focal epilepsy using cortical penicillin injection was used for the epileptic rats. Capsules not implanted in rats served as control. Using magnetic resonance imaging (MRI), the aggregation status of SPIONs contained in the capsules was assessed via measurement of the T₂ relaxivity time of the solutions.

Results: Eight Rats were used for the experiments, with 4 rats in each group (epileptic and sham). One Rat in the sham group died immediately after surgery and 3 rats failed to demonstrate the expected behavior after intervention (2 rats in epileptic group with limited observable seizures and 1 rat in the sham group having repeated seizures). T₂ of the control capsules were significantly lower than those implanted in rats (146 ms vs 7.6 ms, p < 0.001), suggesting a higher degree of SPIONs aggregation in the implanted capsules. No significant difference in T₂ could be demonstrated between epileptic and sham rats.

Conclusions: SPIONs implanted over the cortex of active brain showed an increased aggregation status, confirming their potential as a new marker for brain activity. One of the main advantages of SPIONs is that their aggregation status can be measured at a distance with MRI, taking advantage of its high spatial resolution and imaging capacities. The current model was suboptimal to confirm if epileptic activity can be differentiated from normal brain activity using SPIONs.

Keywords: Brain activity; Epilepsy; Epilepsy surgery; Iron oxide nanoparticles; Superparamagnetism.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Brain* / diagnostic imaging
Capsules
Feasibility Studies
Magnetite Nanoparticles*
Rats
Seizures

Substances

Capsules
Magnetite Nanoparticles