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Nanomaterials 2018, 8(7), 513;

Mechanisms of Cellular Internalization of Quantum Dot® Conjugated Bone Formation Mimetic Peptide CK2.3

Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA
Author to whom correspondence should be addressed.
Received: 28 May 2018 / Revised: 3 July 2018 / Accepted: 6 July 2018 / Published: 9 July 2018
(This article belongs to the Special Issue Nanomaterials for Imaging, Diagnosis or Therapy)
Full-Text   |   PDF [4781 KB, uploaded 9 July 2018]   |  


Osteoporosis is a debilitating skeletal disorder that is characterized by loss of bone density
over time. It affects one in two women and one in four men, age 50 and older. New treatments
that specifically drive bone formation are desperately needed. We developed a peptide, CK2.3, that
acts downstream of the bone morphogenetic protein receptor type Ia and it induces osteogenesis
in-vitro and in-vivo. However, its mechanism of action, especially its mode of uptake by cells
remains unknown. To demonstrate CK2.3 internalization within a cell, we conjugated CK2.3
to Quantum Dot®s (Qdot®s), semiconductor nanoparticles. We purified CK2.3-Qdot®s by size
exclusion chromatography and verified the conjugation and stability using UV/VIS and Fourier
transform infrared spectroscopy. Our results show that CK2.3 was conjugated to the Qdot®s and
the conjugate was stable for at least 4 days at 37 °C. Moreover, CK2.3-Qdot®s exerted biological
response similar to CK2.3. Addition of CK2.3-Qdot®s to cells followed by confocal imaging revealed
that CK2.3-Qdot®s were internalized at 6 h post stimulation. Furthermore, using pharmacological
inhibitors against endocytic pathways, we demonstrated that CK2.3-Qdot®s were internalized by
caveolae. These results show for the first time that the novel peptide CK2.3 is taken up by the cell
through caveolae mediated endocytosis. View Full-Text
Keywords: Bone; Osteoporosis; CK2.3; Qdot®s; Fluorescence imaging; FTIR Bone; Osteoporosis; CK2.3; Qdot®s; Fluorescence imaging; FTIR

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Vrathasha, V.; Booksh, K.; Duncan, R.L.; Nohe, A. Mechanisms of Cellular Internalization of Quantum Dot® Conjugated Bone Formation Mimetic Peptide CK2.3. Nanomaterials 2018, 8, 513.

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