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Dye-loaded lipid nanoparticles

Mise à jour 17 janvier 2018

Lipid nanoparticles are particularly interesting for bioimaging applications because they are composed of fully biodegradable materials and are very easy to fabricate by spontaneous emulsification. To ensure efficient dye loading with minimal leakage from the particles, we followed successfully two concepts of dye design : (i) dyes bearing multiple hydrophobic alkyl chains1 and (ii) cationic cyanine dyes in combination with bulky hydrophobic counterions 2.


Figure 1. Chemical structures of lipophilic cyanine 5.5 and 7.5 dyes (Cy5.5LP and Cy7.5LP) with their bulky hydrophobic counterions and schematic presentation of nano-droplet encapsulating these dyes.

By using bulky hydrophobic counterion tetraphenyl borate (TPB), we were able to increase many-fold the solubility of cyanines dyes in oil and create 90 nm lipid droplets bearing exceptional number of dyes ( 12,000 per droplet, 8 wt% dye loading). The extreme brightness of these NCs (100-fold brighter than quantum dots) enabled to pioneer single particle tracking in vivo in a zebrafish embryo model. Further, using this concept, we have developed FRET nanocarriers loaded with NIR dyes Cy5.5 Cy7.5 (Figure 1) 3. Efficient FRET and excellent brightness of the loaded dyes allowed achieving whole-animal imaging with a very high resolution (Figure 2). Moreover, we were able to accurately resolve the follow-up of nanoparticles integrity directly in the blood circulation of living mice (Figures 2, 3) 3. It was found that lipid nanocarriers despite their liquid core can enter tumors in nearly intact form, showing their capacity to deliver and release their inside target tumors.


Figure 2. FRET imaging of healthy and nude mice at different times after injection with NIR-FRET lipid NCs (1% of Cy5.5LP and Cy7.5LP each).


Figure 3. Concept of FRET NCs that can report on their integrity by change in their emission color.


1) Klymchenko, A.S. ; Roger, E. ; Anton, N. ; Anton, H. ; Shulov, I. ; Vermot, J. ; Mely, Y. ; Vandamme, T.F. Highly lipophilic fluorescent dyes in nano-emulsions : towards bright non-leaking nano-droplets. RSC Advances, 2012, 2, 11876-11886.

2) Kilin, V.N., H. Anton, N. Anton, E. Steed, J. Vermot, T.E. Vandamme, Y. Mely and A.S. Klymchenko, Counterion-enhanced cyanine dye loading into lipid nano-droplets for single-particle tracking in zebrafish. Biomaterials, 2014. 35(18) : p. 4950-4957.

3) Bouchaala, R., N. Anton, H. Anton, T. Vandamme, J. Vermot, D. Smail, Y. Mely and A.S. Klymchenko, Light-triggered release from dye-loaded fluorescent lipid nanocarriers in vitro and in vivo. Colloids and Surfaces B-Biointerfaces, 2017. 156 : p. 414-421.