Long-Term Quantitatively Imaging Intracellular Chloride Concentration Using a Core-/Shell-Structured Nanosensor and Time-Domain Dual-Lifetime Referencing Method

Abstract

Luminescence lifetime-based nanosensors for chloride ions were designed by incorporating a luminescent ruthenium dye [Ru­(1,10-phenanthroline)3] inside silica nanoparticles and chemically labelling their outer surface with chloride ion-sensitive fluorescent dyes (N,N′-bis­(carboxypropyl)-9,9′-biacridine). The nanosensor surface was further functionalized with positively charged amino groups to facilitate intracellular uptake via endocytosis and target lysosomes. The nanosensors have an average diameter of 52 nm and are monodispersed in aqueous solutions. Because of the long lifetime of the reference ruthenium dye, the sensor response can be analyzed using the time-domain dual-lifetime referencing (td-DLR) approach. The use of pulsed excitation in td-DLR rather than intense continuous illumination in ratiometric measurements greatly prevents the dye from photobleaching which significantly improves its measurement stability and reproducibility for long-term monitoring. At optimum conditions, the sensor can measure chloride concentration in the range of 0–200 mM with a large ratiometric signal change from 140.9 to 40.2. Combined with our custom-built microscopic td-DLR system, variations of intracellular chloride concentration in lysosomes were imaged quantitatively with a high spatial resolution and accuracy.

Molecular Probes, Chemosensors, and Nanosensors for Optical Detection of Biorelevant Molecules and Ions in Aqueous Media and Biofluids

“…Recently, a ratiometric sensing strategy which is selective for chloride anions has been evaluated by Wang and coworkers and used for intracellular Cl – quantification . For this purpose, dual fluorescent silica particles ( N12.16 in Figure ) were prepared physically entrapping the [Ru II (1,10-phenanthroline) 3 ] complex (reference dye) and bearing on their surface the Cl – responsive fluorescent dye N , N ′-bis­(carboxypropyl)-9,9′-biacridine (reporter dye), which was grafted onto the surface of the particles by alkoxysilane chemistry.…”

AIEgen‐Based Lifetime‐Probes for Precise Furin Quantification and Identification of Cell Subtypes

“…[ 19 ] Thereby the LRET occurs between PyTPA‐P and ZGO‐NH 2 in PyTPA‐ZGO, leading to the extended lifetime of PyTPA‐P and shortened lifetime of ZGO‐NH 2 . [ 20 ] The PyTPA‐ZGO possesses three lifetime signals: lifetime signal 1 comes from PyTPA‐P labeled as τ P0 , which is at nanosecond level; lifetime signal 2 comes from ZGO‐NH 2 labeled as τ Z0 , which is at microsecond level, and the lifetime signal 3 is a composite‐dual‐lifetime‐signal (CDLS 0 , ). As shown in Figure 1c, PyTPA‐ZGO probe exhibits initial three lifetime signals τ P0 , τ Z0 and CDLS 0 respectively.…”

Strategies to promote permeation and vectorization, and reduce cytotoxicity of metal complex luminophores for bioimaging and intracellular sensing

“…Although useful in the context of Cl À sensing because of local chloride concentration, the particles were found to localise in the lysosome, a common consequence of low endosome escape in nanoparticle uptake. 120 Frasconi et al immobilised the complex [Ru(terpy)(dppz) H 2 O] 2+ , where terpy is 2,2 0 :6 0 ,2 00 -terpyridine, at silica nanoparticles by coordination of a monodentate ligand with nitrile group which anchors the complex to the nanoparticles. The Ru-nanoparticles exhibited low dark cytotoxicity until photoactivation triggered nitrile ligand cleavage and ejection of a highly cytotoxic Ru-aquo solvate complex and separately, paclitaxel drug loaded within the silica nanoparticle.…”

“…Although useful in the context of Cl − sensing because of local chloride concentration, the particles were found to localise in the lysosome, a common consequence of low endosome escape in nanoparticle uptake. 120 …”