• • The second-generation rotaxane transporter [3]R-TCE2 achieves an EC50 of 60 nM (0.18 mol% relative to lipid), a tenfold improvement over first-generation systems, enabling effective K+ transport at concentrations relevant for clinical applications.
• • The tricyclic TCE ring with two K+ recognition sites allows transport of two K+ ions per shuttle cycle, doubling the transport flux and reducing the required transporter concentration for 50% activity to the nanomolar range.
• • The cooperative shuttle-relay mechanism in [3]R-TCE2, where two rings traverse the thread, minimizes shuttle distance and enhances transport efficiency, yielding EC50 values that surpass previous rotaxane-based transporters by an order of magnitude.
• • The reported EC50 of 60 nM positions [3]R-TCE2 among the most active synthetic ion transporters, offering a viable pathway for developing therapeutic agents and biosensing platforms that require precise ion flux control.