Hello: my name is Ricki and I am a PhD student from the University of Southern California (USC). I have a question about CdSe quantum dots I purchased from Ocean Nanotech (https://oceannanotech.com/web/products.php?category3=Quantum_Dots_in_Toluene), specifically the 665 nm-emitting ones (QSR665). I would like to embed these quantum dots onto lipid (dipalmitoyl sn-glycero-palmitoyl, DPPC) vesicles.

I have read numerous papers (https://www.scirp.org/journal/paperinformation.aspx?paperid=86189 and https://pubs.acs.org/doi/10.1021/ja411339f for instance) that describe this process. Briefly, the lipid and QDs are mixed in a chloroform solution (typically 2-4 mM lipid to 100-5000 nM QD) and then deposited as a thin layer onto a surface. The solvent is evaporated and the film is swelled in aqueous solution, with or without an electric current applied. Crucially, the embedding of the hydrophobic QD onto the lipid membrane protects it from degradation in the presence of water.

I have tried duplicating these experiments with these Ocean Nanotech QDs, but I always notice that their fluorescence on the lipid vesicles is completely quenched immediately upon adding the aqueous swelling solution. I used 3-4 mM lipid in combination with many CdSe QD concentration ranges from 0.1 - 250 uM, to no avail. Using the electroformation method also results in vesicle formation, but the CdSe fluorecence remains negligible.

Would you happen to have any suggestions for successfully embedding these quantum dots onto a lipid bilayer, without having the fluorescence disappear after adding water? e.g. different concentration ratios to try, different lipids, etc? Will purchasing the variant Ocean Nanotech QDs with surface modifications (carboxyl, amine, etc) help?

Any help on this would be greatly appreciated.