title: Macrophage uptake of cylindrical microparticles investigated with correlative microscopy.
abstract: Cylindrical particles offer the opportunity to develop controlled and sustained release systems for the respiratory tract. One reason is that macrophages can phagocyte such particles only from either of the two ends. We investigated the uptake behaviour of murine alveolar macrophages incubated with elongated submicron-structured particles. For that purpose, fluorescent model silica nanoparticles were interconnected with the biocompatible polysaccharide agarose, building up cylindrical particles within the pores of track-etched membranes. In contrast to common approaches we determined the uptake at different time points with scanning electron microscopy, fluorescence microscopy, and the combination of both techniques - correlative microscopy (CLEM). As a consequence, we could securely identify uptake events and observe in detail the engulfment of particles and confirm, that phagocytosis could only be observed from the tips of the cylinders. CLEM allowed a comparison of the uptake measured with different techniques at identical macrophages. Qualitative and quantitative evaluation of this cylindrical particle uptake showed substantial differences between fluorescence microscopy, electron microscopy and the combination of both (CLEM) within 24h.
authors.affiliation: Pharmaceutics and Biopharmacy, Philipps University, Marburg, Germany.
authors.forename: Clemens
authors.initials: C
authors.lastname: Tscheka
authors.affiliation: Drug Delivery, Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Center for Infection Research (HZI), Saarbrücken, Germany.
authors.forename: Marius
authors.initials: M
authors.lastname: Hittinger
authors.affiliation: Drug Delivery, Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Center for Infection Research (HZI), Saarbrücken, Germany; Department of Pharmacy, Biopharmaceutics and Pharmaceutical Technology, Saarland University, Saarbrücken, Germany.
authors.forename: Claus-Michael
authors.initials: CM
authors.lastname: Lehr
authors.affiliation: Drug Delivery, Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Center for Infection Research (HZI), Saarbrücken, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Schneider-Daum
authors.affiliation: Pharmaceutics and Biopharmacy, Philipps University, Marburg, Germany; Department of Pharmacy, Biopharmaceutics and Pharmaceutical Technology, Saarland University, Saarbrücken, Germany. Electronic address: Marc.Schneider@mx.uni-saarland.de.
authors.forename: Marc
authors.initials: M
authors.lastname: Schneider
mesh_terms: D000818:Animals; D002460:Cell Line; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008855:Microscopy, Electron, Scanning / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D053758:Nanoparticles / Q000737:chemistry* / Q000378:metabolism*; D010316:Particle Size
keywords: Correlative light and electron microscopy (CLEM); Fluorescence light microscopy (FLM); Microparticles from nanoparticles; Non-spherical particles; Phagocytosis; Scanning electron microscopy (SEM); Shape dependent uptake