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Nanoprobing the acidification process during intracellular uptake and trafficking

: Lerch, Simone; Ritz, Sandra; Bley, Karina; Messerschmidt, Claudia; Weiss, Clemens K.; Musyanovych, Anna; Landfester, Katharina; Mailänder, Volker


Nanomedicine. Nanotechnology, biology and medicine 11 (2015), No.6, pp.1585-1596
ISSN: 1549-9642
ISSN: 1549-9634
Journal Article
Fraunhofer ICT-IMM ()
nanoparticle; intracellular trafficking; acidification; pH responsiveness; Rab-family

Many 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.