title: A new tool to ensure the fluorescent dye labeling stability of nanocarriers: a real challenge for fluorescence imaging.
abstract: Numerous studies on nanocarriers use fluorescent dye labeling to investigate their biodistribution or cellular trafficking. However, when the fluorescence dye is not grafted to the nanocarrier, the question of the stability of the labeling arises. How can it be validated that the fluorescence observed during an experiment corresponds to the nanocarriers, and not to the free dye released from the nanocarriers? Studying the integrity of the labeling is challenging. Therefore, an innovative approach to confirm the labeling stability was developed, based on the transfer of a fluorescent dye from its hosting nanocarrier to a lipophilic compartment. Lipid nanocapsules (LNC) and triglyceride oil were used as models. The protocol involved mixing of LNC suspension and oil, and then separation by centrifugation. The quality of the separation was controlled by light scattering, using the derived count rate tool. Dye transfer from loaded LNCs to the lipophilic compartment or from a lipophilic compartment containing dye to non-loaded LNC was investigated by varying the nature of the dye and the oil, the oil volume and the LNC dilution. Tensiometry was used to define the dye location in the nanocarrier. Results showed that when dyes such as Nile Red and Coumarin-6 are located in oily core, the transfer occurred in a partition-dependent manner. In contrast, when the dye was entrapped in the surfactant shell of LNCs such as lipophilic indocarbocyanines (i.e. DiO, DiI and DiD), no transfer was observed. Dye diffusion was also observed in cell culture, with Nile Red inside lipid bodies of HEI-OC1 cells, without uptake of LNCs. In contrast, DiO-loaded LNCs had to be internalized to observe fluorescence inside the cells, providing a further confirmation of the absence of transfer in this case, and the stability of fluorescence labeling of the LNCs.
authors.affiliation: Micro et Nanomédecines Biomimétiques-MINT, INSERM U 1066, Angers F-49933, France. guillaume.bastiat@univ-angers.fr
authors.forename: Guillaume
authors.initials: G
authors.lastname: Bastiat
authors.forename: Christian Oliver
authors.initials: CO
authors.lastname: Pritz
authors.forename: Clemens
authors.initials: C
authors.lastname: Roider
authors.forename: Florian
authors.initials: F
authors.lastname: Fouchet
authors.forename: Erwann
authors.initials: E
authors.lastname: Lignières
authors.forename: Alexander
authors.initials: A
authors.lastname: Jesacher
authors.forename: Rudolf
authors.initials: R
authors.lastname: Glueckert
authors.forename: Monika
authors.initials: M
authors.lastname: Ritsch-Marte
authors.forename: Anneliese
authors.initials: A
authors.lastname: Schrott-Fischer
authors.forename: Patrick
authors.initials: P
authors.lastname: Saulnier
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Benoit
mesh_terms: D000818:Animals; D002460:Cell Line; D004337:Drug Carriers / Q000008:administration & dosage* / Q000737:chemistry; D005456:Fluorescent Dyes / Q000008:administration & dosage* / Q000737:chemistry; D008055:Lipids / Q000737:chemistry; D051379:Mice; D053769:Nanocapsules / Q000008:administration & dosage* / Q000737:chemistry; D061848:Optical Imaging
chemical_list: D004337:Drug Carriers; D005456:Fluorescent Dyes; D008055:Lipids; D053769:Nanocapsules
keywords: Cell culture; Fluorescent dye; Labeling of nanocarrier; Light scattering; Lipid nanocapsule