Microencapsulation of inorganic nanocrystals into PLGA microsphere vaccines enables their intracellular localization in dendritic cells by electron and fluorescence microscopy

• Published in: Journal of controlled release Vol. 151; no. 3; pp. 278 - 285
• Main Authors: Schliehe, Christopher, Schliehe, Constanze, Thiry, Marc, Tromsdorf, Ulrich I., Hentschel, Joachim, Weller, Horst, Groettrup, Marcus
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 10.05.2011; Elsevier
• Subjects: Animals; Antigenicity; Biodegradation; Biological and medical sciences; Biological Transport; Cells, Cultured; Cross-Priming - immunology; Dendritic Cells - metabolism; Dendritic Cells - ultrastructure; Drug Carriers - chemistry; Drug Compounding; Endosomes - metabolism; Endosomes - ultrastructure; General pharmacology; Immunostimulation; Lactic Acid - chemistry; Lead - chemistry; Medical sciences; Mice; Mice, Inbred C57BL; Microencapsulation; Microscopy, Electron, Transmission; Microscopy, Fluorescence; Microsphere; Microspheres; Nanoparticles - chemistry; Pharmaceutical technology. Pharmaceutical industry; Pharmacology. Drug treatments; Polyglycolic Acid - chemistry; Polylactic acid; Quantum Dots; Sulfides - chemistry; Vaccines - administration & dosage; Vaccines - pharmacokinetics; Biodegradation; Microencapsulation; Immunostimulation; Microsphere; Antigenicity; Polylactic acid; Dendritic cell; Pharmaceutical technology; Biodegradability; Vaccine; Glycolic acid polymer; Electron microscopy; Lactone polymer; Lactic acid polymer; Aliphatic polymer; Microparticle; Copolymer; Fluorescence microscopy; Nanocrystal
• ISSN: 0168-3659; 1873-4995
• DOI: 10.1016/j.jconrel.2011.01.005

Biodegradable poly-(D,L-lactide-co-glycolide) microspheres (PLGA-MS) are approved as a drug delivery system in humans and represent a promising antigen delivery device for immunotherapy against cancer. Immune responses following PLGA-MS vaccination require cross-presentation of encapsulated antigen by professional antigen presenting cells (APCs). While the potential of PLGA-MS as vaccine formulations is well established, the intracellular pathway of cross-presentation following phagocytosis of PLGA-MS is still under debate. A part of the controversy stems from the difficulty in unambiguously identifying PLGA-MS within cells. Here we show a novel strategy for the efficient encapsulation of inorganic nanocrystals (NCs) into PLGA-MS as a tool to study their intracellular localization. We microencapsulated NCs as an electron dense marker to study the intracellular localization of PLGA-MS by transmission electron microscopy (TEM) and as fluorescent labels for confocal laser scanning microscopy. Using this method, we found PLGA-MS to be rapidly taken up by dendritic cells and macrophages. Co-localization with the lysosomal marker LAMP1 showed a lysosomal storage of PLGA-MS for over two days after uptake, long after the initiation of cross-presentation had occurred. Our data argue against an escape of PLGA-MS from the endosome as has previously been suggested as a mechanism to facilitate cross-presentation of PLGA-MS encapsulated antigen. [Display omitted]