Liposome Delivery of Quantum Dots to the Cytosol of Live Cells

Abstract

An increasing number of studies have demonstrated the multiple advantages of using nanocrystals, such as Quantum dots, for biological imaging. Quantum dots functionalized with biomolecules on their surfaces were shown to be able to bind to specific extracellular targets via specific recognition and to be internalized inside the cells, thereby allowing the imaging of intracellular pathways. However, the use of Quantum dots for live tracking of intracellular molecules is relatively limited because of the difficulties encountered during the induction of Quantum dots across living cell membranes. In this study we show that cationic liposomes can deliver low concentrations of non-targeted Quantum dots into the cytosol of living cells via a lipid-mediated fusion with the cell membrane. The intracellular Quantum dots exhibit aggregation that appears dependent upon their concentration, but does not visibly affect cell viability. Our results point towards the use of cationic liposomes as an effective delivery system for targeted Quantum dots within the cell cytosol, which would facilitate live cell imaging of the labeled molecules.

Live Cell Labeling of Glial Progenitor Cells Using Targeted Quantum Dots

“…Cationic liposomes were selected because of their electrostatic interaction with the negatively charged cell membrane, and the OPPC and DOPC+ liposome combination was used primarily in response to published literature that suggested its fusion with the plasma membrane 2,18 as well as our own experiments with the lipofection. 9 Previous results from our lab have shown that cationic liposome fuse with the plasma membrane and release their content into the cytoplasm. This fusion was represented by an increase in plasma membrane after liposome fusion.…”

“…This fusion was represented by an increase in plasma membrane after liposome fusion. 9 Figure 3a depicts a fluorescent image and overlay of extracellular labeling of PDGFR protein domains by direct incubation of GPC PDGF cells with T-QDs. The desired e-PDGFR labeling is seen along the cell periphery, and no cytosolic labeling is observed within the plasma membrane.…”

Entrapment in phospholipid vesicles quenches photoactivity of quantum dots

“…Liposomal QDs show improved shelf life stability and intracellular delivery. 75,76 We have further checked the possibility of intracellular proteins to exert an effect on QD fluorescence. Indeed, in a model solution after incubation at room temperature with BSA, QD fluorescence lifetime decreased ( Figure 9, curve 2 vs 3) and after ∼100 h, the fluorescence was completely quenched (Figure 10).…”

Biopolymer, Dendrimer, and Liposome Nanoplatforms for Optical Molecular Imaging

“…Owing to their hydrophobic surface and potential in vivo toxicity [85,86], the clinical application of QDs is often faced with skepticism. The encapsulation of QDs in liposomes therefore presents an attractive approach to improve QDs' biocompatibility and toxicity [87]. Recently, it was also reported that liposomes consisting of hepatitis B surface antigen and fluorescently labeled polystyrene beads or plasmids were used for tissue and cellular targeting with high specificity [88].…”