Nanoparticles have gained recent attention with an application range spanning from therapeutic drug delivery to sensitive biosensor systems. Quantum dots, specifically, are quickly becoming impressive analytical tools because of their novel optical and electrical properties. Before a quantum dot (QD) can be employed as a biosensor, for instance, studies must be conducted to observe the process of QD entry into biological cells.
The commonly regarded cell entry pathway of QDs is through endocytosis. MHDA-coated CdSe@ZnS QDs and MUHEG-coated CdSe@ZnS QDs enter bovine pulmonary arterial endothelial cells (bPAEC) by nonspecific endocytosis, which was observed by quantitatively measuring QD fluorescence emission within bPAEC via fluorescence microscopy. Experiments showed that cellular uptake of QDs is significantly dependent on QD concentration and cell exposure time to QD solution. It was also observed that MUHEG-capped CdSe@ZnS were more uniformly distributed inside of bPAEC than MHDA-capped CdSe@ZnS QDs. The biodistribution of MHDA-QDs can be attributed to intracellular Ca 2+ concentrations. Divalent metal ions (Ca 2+ specifically) in the HBSS reaction buffer caused MHDA-capped QDs to aggregate in solution prior to cellular absorption, whereas MUHEG-QDs were unaffected. Due to even slight aggregation of MHDA-coated CdSe@ZnS nanoparticles, MUHEG-coated CdSe@ZnS QDs are better candidates for biological applications.
