Photoregulated Sequential Chemical Relay via Artificial Nanochannels

Development of synthetic ion transporters and in situ chemical reaction-mediated communication systems that mimic cellular signaling processes is crucial for preparing protocells to understand complex cellular signaling and related functions. Although there have been advances in synthetic ion transporters, the role of this synthetic ion transporter-mediated inter-vesicular signal transduction remains largely unexplored. Herein, we describe a photoregulated inter-vesicular molecular communication system that employs synthetic ion transporters and a photoresponsive precatalyst. This artificial communication system regulates the transformation of one chemical signal (Zn²⁺) from the sender vesicle into another chemical signal (Cl^-) to the receiver vesicle through a photoregulated chemical reaction in the extravesicular environment. Fluorescence-based ion transport and electrophysiological studies showed that the potent salicylaldehyde-based imine derivatives of 9-alkyl-9<i>H</i>-carbazole-3,6-diamine self-assemble within the lipid bilayer to form supramolecular nanochannels that selectively efflux Zn²⁺ from the sender vesicles. The use of a photoresponsive precatalyst anchored to the outer membrane of the receiver vesicle and the protransporter plays a crucial role in transforming the Zn²⁺-based chemical signal from the sender vesicles to a Cl^--based chemical signal into the receiver vesicle in a controlled manner. The Zn²⁺-bound catalyst-driven hydrolysis facilitates the release of an active transporter, a salicylanilide derivative, from its protransporter to transport Cl^- to a larger population of receiver vesicles, resulting in inter-vesicle signal transduction.