Nanoparticules organiques fluorescentes à base de lipides : intégrité et relargage de principes actifs in vitro et in vivo

Abstract

Understanding the drug release form nanocarriers is fundamental in the development of new effective nanomedicines. However, existing methods, notably dialysis frequently fails to quantifies release of molecules poorly soluble in water and it is not really adapted for in situ measurements in biological media. Here, we have developed a new methodology for quantifying release of fluorescent molecule from lipid nanocarriers (LNCs) using fluorescent correlation spectroscopy (FCS). LNCs, so-called nanoemulsion droplets, encapsulating as a model cargo, the hydrophobic Nile Red derivative NR668, were used as a testing system for release into model biological media. Our studies revealed that standard deviation of fluorescence fluctuation in FCS measurements depends linearly from the loading of the nanocarriers with the dye and it is insensitive to the presence of less bright molecular emissive species in solution. In sharp contrast, classical FCS parameters, such as number and brightness of emissive species are strongly influenced by fluorescence of molecular species in solution. Therefore, only standard deviation of fluorescence fluctuation can directly report on the nanocarriers dye loading without interferences from “parasite” fluorescence because of released dye or auto-fluorescence of the medium. Our method was validated using hydrophobic Nile Red dye, NR668, encapsulated into lipid nanoemulsion. The results suggest that LNCs remain intact in water, whereas in FBS medium, they release their content in a temperature-dependent manner. At 37°C, the release is relatively slow reaching 50% only after 6h of incubation. This method of quantification is simple, because it requires only detection of standard deviation of the signal, so that measurements can be done in principle without any analysis of autocorrelation curve.