Ionophore-Based Ion-Selective Nanosensors from Brush Block Copolymer Nanodots

The selectivity of ionophore-based sensors is crucial to real applications such as clinical diagnostics and bioimaging. Previous ion-selective nanosensors developed from amphiphilic block copolymers are attractive because of simple fabrication, high stability, and versatility. However, the selectivity was reduced compared with polymeric ion-selective membranes. Here, we present ionophore-based nanosensors from graft copolymer nanodots (23.5 ± 3.8 nm in diameter) with significantly improved selectivity and excellent stability against high ionic strength and dilution. The improved selectivity was ascribed to the high ion-carrier stability constants inside the nanodots, with log β values of 7.6 and 8.2 for Na+ and K+, respectively. Besides response in the light absorption mode, an intriguing energy transfer in the nanodots resulted in a ratiometric and dual-emission sensing mode. Nanosensors delivered to HeLa cells through endocytosis were found to accumulate in endosomes and lysosomes. As a preliminary application, the sodium ion concentration in diluted human blood serum was successfully determined.