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.

Study on intracellular delivery of liposome encapsulated quantum dots using advanced fluorescence microscopy

“…Generalov et al . observed a decrease of the QD655 average luminescence decay time upon encapsulation in phospholipid vesicles 39 , but this was not the case in the present study. This confirmed that the luminescence decay behaviour of quantum dots is strongly dependent on their microenvironment.…”

“…30 min. A similar uptake pattern has been reported for QD610-loaded liposomes 33 as well as for QD655 (PEG)-loaded liposomes 39 . The intracellular luminescent spots could be attributed to aggregates of quantum dots formed intracellularly 19,20,75,76 .…”

Dual-Ligand Surface Passivation Enables Monodisperse Ag2S Colloidal Quantum Dots for Efficient Near-Infrared Photothermal Therapy

“…The result revealed that the control CQDs have an average diameter of 22.9 nm, whereas the dual-ligand CQDs exhibit a smaller average diameter of 12.4 nm (Figure S2). The increased diameter in the control CQDs is attributed to their CQD fusion, which increases the hydrodynamic diameter of CQDs . In contrast, the dual-ligand CQDs exhibit diameters measured in DLS (12.4 nm) that are similar to those measured by TEM (11.8 nm), indicating a more uniform size distribution with a minimized CQD fusion.…”

“…The increased diameter in the control CQDs is attributed to their CQD fusion, which increases the hydrodynamic diameter of CQDs. 32 In contrast, the dualligand CQDs exhibit diameters measured in DLS (12.4 nm) that are similar to those measured by TEM (11.8 nm), indicating a more uniform size distribution with a minimized CQD fusion.…”