Atomic Force Microscopy-based Cell Nanostructure for Ligand-conjugated Quantum Dot Endocytosis

Abstract

While it has been well demonstrated that quantum dots (QDs) play an important role in biological labeling both in vitro and in vivo, there is no report describing the cellular nanostructure basis of receptor-mediated endocytosis. Here, nanostructure evolution responses to the endocytosis of transferrin (Tf)-conjugated QDs were characterized by atomic force microscopy (AFM). AFM-based nanostructure analysis demonstrated that the Tf-conjugated QDs were specifically and tightly bound to the cell receptors and the nanostructure evolution is highly correlated with the cell membrane receptor-mediated transduction. Consistently, confocal microscopic and flow cytometry results have demonstrated the specificity and dynamic property of Tf-QD binding and internalization. We found that the internalization of Tf-QD is linearly related to time. Moreover, while the nanoparticles on the cell membrane increased, the endocytosis was still very active, suggesting that QD nanoparticles did not interfere sterically with the binding and function of receptors. Therefore, ligand-conjugated QDs are potentially useful in biological labeling of cells at a nanometer scale.

Hypoxia: dual effect on the expression of transferrin receptor in human melanoma A375 cell line

“…It was reported that anti-apoptotic proteins IAP-2 and the proapoptotic protein Bax can shift the balance between cell apoptosis and proliferation during hypoxia as hypoxia can induce apoptosis, prevent cell death, or even stimulate cell proliferation (19)(20)(21)(22)(23). Bax is the family of BCL-2 proteins which can form protein dimers with BCL-2 (24,25), and the BCL-2 ⁄ Bax ratio is believed to control the balance between life and death within a cell (23,(25)(26)(27).…”

Nanomedicine in Hepatocellular Carcinoma: A New Frontier in Targeted Cancer Treatment

“…In vitro cytotoxicity in HepG2 and KC cells and in vivo transfection activity in HepG2 xenografts concluded high loading efficiency along with excellent cell targeting ability of Tf-conjugated NPs Transferrin [249] Quantum dots (nanocrystales) N/A…”

Optical Biosensors Based on Semiconductor Nanostructures

“…Among the most referenced methods for a detailed study of this internalization are confocal microscopy [ 21 ] and flow cytometry [ 22 ]. Related studies show that diffusive processes taking place to reach osmotic equilibrium are not efficient enough and should be enhanced by active receptor mediated endocytotic pathways [ 23 , 24 ]. For this latter point, biofunctionalization with carrier molecules is a key issue.…”

“…PEG chains allow also subsequent binding to a protein through amino terminal groups in the chain [ 29 ]. Among interesting proteins linked to QDs we can mention some with membrane access role such as transferring [ 24 ] though conjugation at the aminoacid scale has been also reported to be effective with histidine [ 15 ] and cysteine [ 18 ], both showing metal affinity interactions and thus prone also to direct bonding to QDs. Relevantly, gastric administration of gluthathione-QD conjugates has been proved to be effective to induce QD fluorescence in the endoderm of invertebrates [ 30 ].…”