In-vitro real-time magnetic recording of neuronal activity on spinal cord slices

Recording the neural activity that originates from action potential dynamics has long been a major pursuit in neuroscience and, specifically, to develop neural interfaces, which are crucial for probing and understanding the nervous tissue. Conventional electrodes and emergent optical imaging (using genetically encoded fluorescence indicators) are complementary technologies to measure neuronal activity in-vivo but present intrinsic and general physical constraints. While optical imaging is difficult to translate in humans due to the strong genetic perturbations it involves, recordings through rigid implanted electrodes get frequently compromised over time by the foreign body reaction of the tissue that hinders the charge transfer to the electrode. In this scenario, magnetic sensing technologies can open further possibilities. Their working principle does not require intimate contact or charge transfer with the neural tissue and allows for well-tested soft polymeric coatings, which can facilitate the long-term functionality of implanted monitoring interfaces. Here, we report on the development of spintronic-based magnetic sensors able to detect neuronal activity emerging from spinal cord slices in physiological conditions at room temperature and with no magnetic shielding. We pharmacologically weaken synaptic inhibition inducing a switch from random to synchronous generation of action potentials, characterized by the appearance of slow-paced bursting in SCSs. The biological nature of the signals recorded was assessed by pharmacological removal of action potentials by tetrodotoxin and also by performing live Ca2+ imaging recordings simultaneously with magnetophysiology. Our results pave the way towards developing implanted devices that detect magnetic fields from neuronal activity for daily life applications.