Transfer of lipophilic markers from PLGA and polystyrene nanoparticles to caco-2 monolayers mimics particle uptake.
OBJECTIVE
The objective of this study was to evaluate nanoparticle uptake by the Caco-2 monolayer model in vitro. Special emphasis was placed on the localization and the quantification of the uptake of fluorescently labeled polystyrene and poly(lactic-co-glycolic acid) (PLGA) nanoparticles.


METHODS
Intracellular fluorescence was localized by fluorescence and confocal laser scanning microscopy. Particle uptake was quantified either directly, by counting internalized nanoparticles after separation from the Caco-2 monolayers, or indirectly, by extraction of the lipophilic fluorescence marker. In vitro release studies of lipophilic markers from nanoparticles were performed in standard buffer systems and buffer systems supplemented with liposomes.


RESULTS
Instead of uptake of polystyrene and PLGA nanoparticles by Caco-2 monolayers an efficient transfer of lipophilic fluorescence markers from nanoparticles into Caco-2 cells with subsequent staining of intracellular lipophilic compartments was observed. Whereas in standard buffer no release of fluorescent marker from polystyrene and PLGA nanoparticles was observed, the release studies using liposome dispersions as receiver revealed an efficient transfer of fluorescent marker into the liposome dispersion.


CONCLUSIONS
The results suggest that the deceptive particle uptake is caused by a collision-induced process facilitating the transfer of lipophilic fluorescent marker by formation of a complex between the nanoparticles and the biomembranes. Diffusion of the marker within this complex into lipophilic compartments of the cell strongly affects quantitative evaluation of particle uptake.
Pietzonka
Peter
P
Institute of Pharmaceutical Sciences, ETH Zurich.
Rothen-Rutishauser
Barbara
B
Langguth
Peter
P
Wunderli-Allenspach
Heidi
H
Walter
Elke
E
Merkle
Hans P
HP
D001692:Biological Transport; D018938:Caco-2 Cells; D004058:Diffusion; D005456:Fluorescent Dyes / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D019344:Lactic Acid; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology; D010316:Particle Size; D010539:Permeability; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers; D011137:Polystyrenes
D005456:Fluorescent Dyes; D011108:Polymers; D011137:Polystyrenes; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid