Dual color pH probes made from silica and polystyrene nanoparticles and their performance in cell studies

Ratiometric green-red fluorescent nanosensors for fluorometrically monitoring pH in the acidic range were designed from 80 nm-sized polystyrene (PS) and silica (SiO₂) nanoparticles (NPs), red emissive reference dyes, and a green emissive naphthalimide pH probe, analytically and spectroscopically characterized, and compared regarding their sensing performance in aqueous dispersion and in cellular uptake studies. Preparation of these optical probes, which are excitable by 405 nm laser or LED light sources, involved the encapsulation of the pH-inert red-fluorescent dye Nile Red (NR) in the core of self-made carboxylated PSNPs by a simple swelling procedure and the fabrication of rhodamine B (RhB)-stained SiO₂-NPs from a silane derivative of pH-insensitive RhB. Subsequently, the custom-made naphthalimide pH probe, that utilizes a protonation-controlled photoinduced electron transfer process, was covalently attached to the carboxylic acid groups at the surface of both types of NPs. Fluorescence microscopy studies with the molecular and nanoscale optical probes and A549 lung cancer cells confirmed the cellular uptake of all probes and their penetration into acidic cell compartments, i.e., the lysosomes, indicated by the switching ON of the green naphthalimide fluorescence. This underlines their suitability for intracellular pH sensing, with the SiO₂-based nanosensor revealing the best performance regarding uptake speed and stability.

An emissive dual-sensitized bimetallic Eu2III-bioprobe: design strategy, biological interactions, and nucleolus staining studies

A dual sensitized Eu2III–bioprobe (1) offers incredible opportunities for fine-tuning and exploring a strongly luminescent probe as a nucleolus staining agent.

Lysosome-targeting luminescent lanthanide complexes: From molecular design to bioimaging

Lysosomes are essential acidic cytoplasmic membrane-bound organelles in human cells that play a critical role in many cellular events. A comprehensive understanding of lysosome-specific imaging can ultimately help us to...

Cyclotriphosphazene-Based "Butterfly" Fluorescence Probe for Lysosome Targeting

A cyclotriphosphazene-based "butterfly" fluorescence probe HCCP-MNI bearing two naphthalimide and morpholine units were developed for lysosome targeting. The synthesized HCCP-MNI exhibited stable fluorescence signals and was cytocompatible in the given concentration range. Co-localization experimental results showed that cells treated with the HCCP-MNI and a commercial dye (Lyso-Tracker Red DND-99) had overlapped fluorescence signals, demonstrating its targeting specificity to lysosomes. The developed HCCP-MNI may be used for cell tracking applications associated with the functionalities of lysosomes.

Luminescent naphthalimide-tagged ruthenium(ii)–arene complexes: cellular imaging, photocytotoxicity and transferrin binding

Two luminescent ruthenium(ii)–arene complexes containing a naphthalimide tagged morpholine moiety were studied for their biomaging, transferrin-binding and phototherapeutic activity.

Engineering diformyl diaryldipyrromethane into a molecular keypad lock

A diaryldipyrromethane-based acyclic system acts as a photolabile sequential chemosensor for both anions and cations via ESIDPT and deprotonation, which is engineered into a fluorescent molecular keypad lock system.