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Published on: June 8, 2012
Macrophage uptake of cylindrical microparticles investigated with correlative microscopy
Clemens Tscheka1, Marius Hittinger2, Claus-Michael Lehr3
1Pharmaceutics and Biopharmacy, Philipps University, Marburg, Germany.
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.
Insights
Macrophages engulf cylindrical particles only at their ends. This study used advanced microscopy to confirm this unique phagocytosis behavior, crucial for developing new respiratory drug delivery systems.
Area of Science:
- Biomaterials science
- Cell biology
- Nanotechnology
Background:
- Cylindrical particles are promising for controlled drug release in the respiratory tract.
- Macrophages phagocytose particles, influencing drug delivery and clearance.
- Particle shape significantly impacts cellular uptake mechanisms.
Purpose of the Study:
- To investigate the phagocytosis of cylindrical nanoparticles by murine alveolar macrophages.
- To elucidate the specific uptake mechanisms and kinetics of these particles.
- To compare the efficacy of different microscopy techniques in analyzing cellular uptake.
Main Methods:
- Fabrication of fluorescent, submicron-structured cylindrical silica-agarose particles.
- Incubation of particles with murine alveolar macrophages.
- Analysis of particle uptake using scanning electron microscopy (SEM), fluorescence microscopy, and correlative light and electron microscopy (CLEM).
Main Results:
- Phagocytosis of cylindrical particles by macrophages was confirmed to occur exclusively from the particle ends.
- Correlative microscopy (CLEM) provided detailed insights into the engulfment process.
- Significant quantitative and qualitative differences in uptake assessment were observed between SEM, fluorescence microscopy, and CLEM within 24 hours.
Conclusions:
- The end-on phagocytosis mechanism of cylindrical particles by macrophages is confirmed.
- CLEM offers a powerful tool for detailed and comparative analysis of cellular uptake.
- Understanding these uptake dynamics is vital for designing effective nanoparticle-based respiratory drug delivery systems.
