PNIPAM-based extracellular K+ fluorescent sensor for high-throughput analysis

We report on the fabrication of K+ fluorescent sensor P2 based on thermoresponsive poly(N-isopropylacrylamide) and small molecule K+ fluorescent sensor KS. P2 changed its size with a range from 35 degrees C to 42 degrees C and exhibited lower critical solution temperature (LCST) at 38 degrees C. The LCST affected the polymer's nanostructures and microenvironment of KS, which in turn affected P2's fluorescence intensities and responses to K+. Furthermore, P2 exhibited high selectivity and sensitivity to K+ with a dynamic response range from 1 to 20 mM, enabling its suitableness for extracellular K+ analysis. The sensor was further used to in situ monitor the K+ fluctuation of Escherichia coli and B. Subtilis 168 bacteria under lysozyme stimulation in 96 well plate by a high throughput analysis approach, and cell species dependent K+ release was observed. The PNIPAM-based K+ sensor P2 shows potential application in antimicrobial drugs/peptides screening.

Automated summary

A K+ fluorescent sensor P2 was fabricated based on thermoresponsive poly(N-isopropylacrylamide) and small molecule K+ fluorescent sensor KS, showing high selectivity and sensitivity to K+. P2 changed its size at a specific temperature range and responded to K+, suitable for extracellular K+ analysis.