Cellular Signalling Pathway Regulation via Polyelectrolyte-Graphene Oxide Ionic Bipolar Junction Transistor

Calcium homeostasis is essential for a wide range of physiological functions, from muscle contraction and neurotransmitter release to bone health and blood clotting. Abnormal calcium release from sarcoplasmic reticulum also results in arrhythmias and hypertension. Spheroid formation is a process where cells aggregate and self-organize into three-dimensional spherical structures in a low-attachment surface. The device fabricated with poly(diallyldimethylammonium chloride) (PDADMAC) coated graphene oxide (GO) membrane works as an ionic bipolar junction transistor (IBJT) with CaCl₂/PDADMAC as the emitter and MgCl₂/PDADMAC as the collector, regulating calcium ion flows under various collector-emitter voltage (V_CE) and base-emitter voltage (V_BE). It is observed that vascular smooth muscle cells (VSMC) were more compactly aligned after voltage stimulation, accompanied by a significant uprush of calcium ionic current. Also, the slight condensation of spheroids overtime and an increase of fluorescence intensity are observed, indicating stronger cytoplasmic protein activities. Our device demonstrated its potential in regulating cellular metabolism by providing ionic signals such as calcium and magnesium via external electrical stimulations. The device paves the way for in vitro Ca²⁺-disease modeling for cardiovascular diseases like hypertension, cardiac arrhythmias and atherosclerosis.