A silica supported tricarbocyanine based pH nanosensor with a large Stokes shift and a near infrared fluorescence response: performance in vitro and in live cells

Abstract

We report the synthesis of a near-infrared (NIR) fluorescent pH probe with a remarkable Stokes shift (∼135 nm) based on a tricarbocyanine (Cy-PIP). The fluorescent molecule was anchored to SiO₂ nanoparticles (Cy-PIP@SiO₂) and is capable of monitoring pH changes within the physiological range (pH 6-8). The Cy-PIP@SiO₂ nanoparticles were successfully internalized by HeLa cells as shown by fluorescence confocal microscopy, while flow cytometry revealed pH fluctuations during the endocytic pathway.