Rational Design of a Polymer-Based Ratiometric K⁺ Indicator for High-Throughput Monitoring Intracellular K⁺...

Area of Science:

• Biochemistry
• Analytical Chemistry
• Materials Science

Background:

• Highly selective fluorescent potassium ion (K+) sensors are crucial for understanding biological processes.
• Ratiometric K+ sensors, emitting dual wavelengths for quantitative analysis, are highly sought after.

Purpose of the Study:

• To develop the first polymer-based ratiometric fluorescent K+ indicator (PK1) for quantitative detection in aqueous solutions.
• To enable high-throughput monitoring of K+ fluctuations in living cells.

Main Methods:

• Synthesized PK1 by conjugating a K+ probe and a red emission dye to a hydrophilic polymer.
• Formed stable nanoparticles of PK1 in aqueous solutions, functional in 100% water.
• Validated PK1's sensitivity, selectivity, and linear correlation with K+ concentration.

Main Results:

• PK1 exhibited a sevenfold fluorescence enhancement upon K+ interaction (1000 mM) and was inert to other ions and pH variations.
• The fluorescence intensity ratio showed a linear correlation with log [K+] (2-500 mM, R² = 0.998).
• PK1 demonstrated successful quantitative detection in K+-rich samples and was internalized by live cells with no cytotoxicity.

Conclusions:

• PK1 is a sensitive, selective, and quantitative ratiometric fluorescent K+ sensor suitable for aqueous solutions and live-cell imaging.
• Its polymer-based design and nanoparticle formation offer advantages for biological applications.
• PK1 facilitates high-throughput, time-saving monitoring of K+ fluctuations, broadening the design of fluorescent K+ sensors.