Turning the lights on with Quantum dots labeled liposomes

VALERIA SIGOT Y THOMAS JOVIN

Conferencia; XLI Reunión Anual de la Sociedad Argentina de Biofísica (SAB); 2012

The combination of liposomes and imaging probes such as Quantum Dots (QDs) in a single nanoparticle offers an excellent tool for understanding the mechanisms of liposome uptake, required to improve the efficiency of gene or drug delivery. In our strategy, biotinylated lipid particles (BLPs), ~100 nm size, were loaded with red emitting QD655 and surface coated with green emitting QD525 conjugated to EGF (Epidermal Growth Factor) ligand. This dual-color approach was employed to monitor the specificity of BLPs binding and uptake in A431 cells from human epidermoid carcinoma over-expressing the EGF receptor (EGFR) by confocal fluorescence microscopy. BLPs were formulated with 1.4% and 2.7 % of PEG-lipids composed by either a fusogenic or a pH-sensitive lipid to favor endosomal escape of the encapsulated QDs. With this approach, colocalized red-green dots indicated specific uptake, whereas the sole detection of red fluorescence evidenced unspecific binding of non-targeted BLP-QD655. The dual-color QD labeling strategy allows the immediate detection of targeted BLPs from the untargeted counterparts, as well as the presence of free EGF-QD525 complexes during live cell imaging. The chemistry of conjugation between EGF ligand, the QDs, and the BLPs in a single lipid particle, involves only biotin-streptavidin interactions. From a therapeutic point of view, the specificity displayed by the targeted BLPs may provide a platform for testing the delivery of anti-tumorigenic drugs into tumor cells overexpressing the EGFR. This approach was also intended to elucidate the fate of lipid particles in real time, taking advantages of the photo-stability and bright fluorescence of QDs, and to provide refined information about subcellular barriers to gene or drug delivery.