Lerch, SimoneSimoneLerchRitz, SandraSandraRitzBley, KarinaKarinaBleyMesserschmidt, ClaudiaClaudiaMesserschmidtWeiss, Clemens K.Clemens K.WeissMusyanovych, AnnaAnnaMusyanovychLandfester, KatharinaKatharinaLandfesterMailänder, VolkerVolkerMailänder2022-03-052022-03-052015https://publica.fraunhofer.de/handle/publica/24007510.1016/j.nano.2015.04.010Many nanoparticular drug delivery approaches rely on a detailed knowledge of the acidification process during intracellular trafficking of endocytosed nanoparticles (NPs). Therefore we produced a nanoparticular pH sensor composed of the fluorescent pH-sensitive dual wavelength dye carboxy seminaphthorhodafluor-1 (carboxy SNARF-1) coupled to the surface of amino-functionalized polystyrene NPs (SNARF-1-NP). By applying a calibration fit function to confocal laser scanning microscopy (CLSM) images, local pH values were determined. The acidification and ripening process of endo/lysosomal compartments containing nanoparticles was followed over time and was found to progress up to 6 h to reach an equilibrium pH distribution (maximum pH 5.2 [± 0.2]). The SNARF-1-NP localization in endo/lysosomal compartments was confirmed by transmission electron microscopy (TEM) and quantitative co-localization analysis with fluorescent endolysosomal marker Rab-proteins by confocal laser scanning microscopy (CLSM). The herein described nanoparticular pH-sensor is a versatile tool to monitor dynamic pH processes inside the endolysosomal compartments.ennanoparticleintracellular traffickingacidificationpH responsivenessRab-family610journal article