Observation of topological action potentials in engineered tissues

The interface between two tissues can have very different bioelectrical properties compared to either tissue on its own. Here we show that an interface between non-excitable tissues can be electrically excitable because of an interaction between the currents passing through the gap junctions—electrically resistive intercellular connections—and the non-linear current–voltage dependence in the ion channels on either side of the interface. Our theory shows that this topologically robust excitability occurs over a far larger range of ion channel expression levels than can support excitability in the bulk. The corresponding interfacial action potentials can cause local elevations in calcium concentration, possibly providing a bioelectrical mechanism for interface sensing. The observed topological action potentials point to the possibility of other types of topological effect in electrophysiology and at other diffusively coupled interfaces.