50nW 5kHz-BW opamp-less ΔΣ impedance analyzer for brain neurochemistry monitoring

Potassium (K+) and sodium (Na+) ions are the main signal carriers in the nervous system. The difference in the concentration of both K+ and Na+ across the neuron cell membrane, as regulated by respective ion channels, plays a critical role in the propagation of action potentials, the spike-like signals neurons communicate with, as shown in Fig. 17.5.1 (top, left and middle). Due to their significant role in neuronal signaling, K+ channel malfunctions are linked to over 100 neurological disorders, such as schizophrenia, Alzheimer's disease, spreading depression, and epilepsy. Selective real-time sensing of K+ concentration (denoted as [K+]) is therefore critical for the advancement of many neurological therapies.