A hemicyanine-based optical probe for biomembranes and intracellular pH sensing

The hemicyanine-based fluorescent probe L3 was demonstrated as a suitable membrane physiological pH probe. L3 easily interacted with the lipid components and anchored in inner membrane and gave a red fluorescence signal (~ 650 nm) in neutral or acidic pH, while the emission switching off when intramembrane pH varied to basic. Moreover, the absorption color of L3 changed from purple red to colorless with increasing pH. Thus L3 served as the pH-dependent modulator, a dual optical biomembranes pH sensing probe, showing good linear relationship in physiological pH range 7.0-8.5 or 7.5-9.0. The liposomes prepared under random pH and suspensions of gastric cancer cells (HGC-27) samples were used for verification of proposed intracellular pH sensing method, and satisfied results were obtained.