Structural and physicochemical aspects of silica encapsulated ZnO quantum dots with high quantum yield and their natural uptake in HeLa cells.

Abstract

Photoluminescent semiconductor quantum dots (QDs) are of significant interest for bioimaging and fluorescence labeling. In this regard, we describe here the design of high sensitivity and high specificity non-toxic ZnO QDs (∼5 nm) with long-term stability of up to 12 months. The embedding of ZnO QDs on silica nanospheres led to significant increase in photoluminescence intensity rendering them highly bright QD-based probes. The QDs were characterized in vitro with respect to cancer cells (HeLa) and evaluated in terms of viability, fluorescence and cytoskeletal organization. The immobilization of ZnO QDs on silica nanospheres promoted the internalization and enhanced fluorescence emission of HeLa cells. The fluorescence emission from QDs was stable for 3 days, indicating excellent stability toward photobleaching. Cytoskeletal reorganization was observed after internalization of QDs such that the ZnO QDS on silica nanospheres resulted in broadening of the actin cytoskeleton. The study underscores that ZnO QDs immobilized on Si nanospheres are promising for tracking cancer cells in cell therapy.