title: Entrapment in phospholipid vesicles quenches photoactivity of quantum dots.
abstract: Quantum dots have emerged with great promise for biological applications as fluorescent markers for immunostaining, labels for intracellular trafficking, and photosensitizers for photodynamic therapy. However, upon entry into a cell, quantum dots are trapped and their fluorescence is quenched in endocytic vesicles such as endosomes and lysosomes. In this study, the photophysical properties of quantum dots were investigated in liposomes as an in vitro vesicle model. Entrapment of quantum dots in liposomes decreases their fluorescence lifetime and intensity. Generation of free radicals by liposomal quantum dots is inhibited compared to that of free quantum dots. Nevertheless, quantum dot fluorescence lifetime and intensity increases due to photolysis of liposomes during irradiation. In addition, protein adsorption on the quantum dot surface and the acidic environment of vesicles also lead to quenching of quantum dot fluorescence, which reappears during irradiation. In conclusion, the in vitro model of phospholipid vesicles has demonstrated that those quantum dots that are fated to be entrapped in endocytic vesicles lose their fluorescence and ability to act as photosensitizers.
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.
authors.forename: Roman
authors.initials: R
authors.lastname: Generalov
authors.forename: Simona
authors.initials: S
authors.lastname: Kavaliauskiene
authors.forename: Sara
authors.initials: S
authors.lastname: Westrøm
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.forename: Solveig
authors.initials: S
authors.lastname: Kristensen
authors.forename: Petras
authors.initials: P
authors.lastname: Juzenas
mesh_terms: D005453:Fluorescence; D005609:Free Radicals; D008081:Liposomes; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D050997:Nanomedicine; D055620:Optical Phenomena; D010316:Particle Size; D010743:Phospholipids; D010778:Photochemotherapy; D010782:Photolysis; D017319:Photosensitizing Agents; D045663:Quantum Dots
chemical_list: D005609:Free Radicals; D008081:Liposomes; D010743:Phospholipids; D017319:Photosensitizing Agents