title: Nanoprobing the acidification process during intracellular uptake and trafficking.
abstract: 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 6h to reach an equilibrium pH distribution (maximum pH5.2 [±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.
  
  
  BACKGROUND
  In this interesting article, the authors elegantly designed a nanoparticular pH sensor with fluorescence probe with the capability to measure intracellular and intravesicular pH changes. The application of this method would enable the further understanding of nanoparticle uptake and intracellular physiology.
authors.affiliation: Max-Planck-Institute for Polymer Research, Mainz, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Lerch
authors.affiliation: Max-Planck-Institute for Polymer Research, Mainz, Germany; Institute of Molecular Biology (IMB) gGmbH, Mainz, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Ritz
authors.affiliation: Max-Planck-Institute for Polymer Research, Mainz, Germany.
authors.forename: Karina
authors.initials: K
authors.lastname: Bley
authors.affiliation: Max-Planck-Institute for Polymer Research, Mainz, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Messerschmidt
authors.affiliation: Max-Planck-Institute for Polymer Research, Mainz, Germany; University of Applied Sciences Bingen, Bingen, Germany.
authors.forename: Clemens K
authors.initials: CK
authors.lastname: Weiss
authors.affiliation: Max-Planck-Institute for Polymer Research, Mainz, Germany; Fraunhofer ICT-IMM, Mainz, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Musyanovych
authors.affiliation: Max-Planck-Institute for Polymer Research, Mainz, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Landfester
authors.affiliation: Max-Planck-Institute for Polymer Research, Mainz, Germany; 3rd Department of Medicine (Hematology, Oncology, and Pneumology), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany. Electronic address: mailaend@mpip-mainz.mpg.de.
authors.forename: Volker
authors.initials: V
authors.lastname: Mailänder
mesh_terms: D000143:Acids / Q000737:chemistry*; D001578:Benzopyrans / Q000737:chemistry; D001692:Biological Transport; D002138:Calibration; D004705:Endocytosis; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015335:Molecular Probes; D049329:Nanostructures; D009284:Naphthols / Q000737:chemistry; D012235:Rhodamines / Q000737:chemistry
chemical_list: D000143:Acids; D001578:Benzopyrans; D015335:Molecular Probes; D009284:Naphthols; D012235:Rhodamines; C091666:seminaphthorhodaminefluoride
keywords: Acidification; Intracellular trafficking; Nanoparticle; Rab-family; pH responsiveness