Potassium-Induced Emission Enhancement of Bovine Serum Albumin-Stabilized Red-Emitting Au Nanoclusters: Mechanism and Application to Blood Plasma

Abstract

Aggregation-induced emission (AIE) enhancement is attractive for bioimaging as it offers higher quantum yields (QYs) from fluorophores via modulation of their immediate environment. Fluorophores with high QYs are essential probes for investigating the spatiotemporal distribution of physiologically important metal ions such sodium and potassium. Potassium ions are vital for normal function of living organisms. The research reported here evaluates the emission intensity of the bovine serum albumin-stabilized red-emitting gold nanoclusters (BSA-rAuNCs) upon uptake of K+. The integrated sphere method was used to determine the absolute QYs and a custom-built fluorescence setup recorded the emission spectra of BSA-rAuNCs. Enhancement of emission intensity was observed upon increasing K+ concentration, within the physiological concentration range of 0 - 150 mM. The emission enhancement was correlated with the particle size and charge analysis. Aggregation of BSA-rAuNCs was found to be responsible for the observed emission enhancement. The QY of BSA-rAuNCs in bovine blood plasma was found to be four times lower than corresponding QY in water.