New nanostructured extracellular potassium ion probe for assay of cellular K⁺ transport

The concentration of potassium ion is an important indicator for human health, and its abnormality is often accompanied by various diseases. However, most tools currently used to study potassium ion transport are low throughput. Herein, we reported a new K⁺ fluorescent nanoprobe CP1-KS with high selectivity and sensitivity to K⁺ (fluorescence enhanced factor was up to 9.91 at 20 mM K⁺). The polymeric fluorescent probe CP1-KS was composed of the small-molecular K⁺ indicator KS and amphiphilic copolymer CP1. This sensor can be easily and uniformly dispersed in cell culture medium and is suitable for high throughput analysis. To assess the utility of the probe CP1-KS in biological field, this probe was employed as an extracellular fluorescent probe to monitor the efflux of K⁺ from cells (E coli, B. Subtilis 168, Hela and MCF-7 cells) under various stimulation including lysozyme, nigericin, digitonin, and ATP. Results demonstrated that CP1-KS is an effective analysis tool for extracellular K⁺ concentration. We believe that the nanoprobe has great potential in antibacterial drug screening, K⁺ ionophore function, K⁺ channel activity, cell membrane permeability analysis or other K⁺ related field in the future.