In situ monitoring and unveiling of K+ ions transmembrane process via sensitive fiber-optic plasmonic spectral combs

Potassium ions ( K + ) transmembrane transport is essential for regulating various physiological processes . Herein, a label-free tilted fiber Bragg grating (TFBG)-assisted plasmonic sensor was proposed and experimentally demonstrated for measuring K + transmembrane movement in situ and continuously. The sensor was coated with valinomycin-modified vesicular liposome , providing an exceptional capability for selectively capturing and transporting K + through the liposome’s bilayer membrane . A differential demodulation method was proposed, by which great advancements were achieved in unveiling K + transmembrane process showing three stages in real time. In particular, not only does the sensor sensitively detect low K + level (detection limit down to 8.5 pM) but also successively decouple bulk and surface effects involved in transmembrane dynamics, along with additional advantage of resistance to temperature and light power fluctuations. These advancements represent great progress in revealing K + transmembrane movement and highlight the potential for monitoring transmembrane-related cellular signaling pathways like cell proliferation and apoptosis.