Abstract
Magnetoencephalography has been established nowadays as a crucial in vivo technique for clinical and diagnostic applications due to its unprecedented spatial and temporal resolution and its non-invasive methods. However, the innate nature of the biomagnetic signals derived from active biological tissue is still largely unknown. One alternative possibility for in vitro analysis is the use of magnetic sensor arrays based on Magnetoresistance. However, these sensors have never been used to perform long-term in vitro studies mainly due to critical biocompatibility issues with neurons in culture. In this study, we present the first biomagnetic chip based on magnetic tunnel junction (MTJ) technology for cell culture studies and show the biocompatibility of these sensors. We obtained a full biocompatibility of the system through the planarization of the sensors and the use of a three-layer capping of SiO2/Si3N4/SiO2. We grew primary neurons up to 20 days on the top of our devices and obtained proper functionality and viability of the overlying neuronal networks. At the same time, MTJ sensors kept their performances unchanged for several weeks in contact with neurons and neuronal medium. These results pave the way to the development of high performing biomagnetic sensing technology for the electrophysiology of in vitro systems, in analogy with Multi Electrode Arrays.
Highlights
In the last 20 years, the study of the magnetic field generated by the electrical activity of the brain has revolutionized neuroscience
In the present work we investigate in detail the biocompatibility of magnetic tunnel junction (MTJ) sensors with murine embryonic hippocampal neurons cultured on the top of the device by viability assays, immunocytochemistry and patch-clamp recordings
In the sensors used in this work, aiming at demonstrating the biocompatibility, maximum Tunneling Magnetoresistance (TMR) variations between 20 and 50% were obtained, mainly depending on the
Summary
In the last 20 years, the study of the magnetic field generated by the electrical activity of the brain has revolutionized neuroscience. Magnetoencephalography (MEG), due to its unprecedented spatial and temporal resolution (Sander et al, 2012; Borna et al, 2017), gained wide clinical applications in detecting and localizing pathological cortical activity in patients with brain tumors or intractable epilepsy (Stufflebeam, 2011). During the last decade, there has been an increasing need to extend biomagnetic signal detection to microscale for higher spatial resolution. As described in (Hall et al, 2012), the magnetic field decays one order of magnitude faster than the electric field. In this context, there is evident crucial interest in developing devices for local magnetic recording in in-vitro systems
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