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Influence of cell-internalization on relaxometric, optical and compositional properties of targeted paramagnetic quantum dot micelles.

Abstract：

:Quantum dot micelles (pQDs) with a paramagnetic coating are promising nanoparticles for bimodal molecular imaging. Their bright fluorescence allows for optical detection, while their Gd payload enables visualization with contrast-enhanced MRI. A popular approach in molecular MRI is the targeting of abundantly expressed cell surface receptors. Ligand-receptor binding often results in cell internalization of the targeted contrast agent. The interpretation of molecular imaging with pQDs therefore requires knowledge about the consequences of cellular internalization for their relaxometric, optical and compositional properties. To study these, Cd-containing core-shell-shell QDs coated with a monolayer of lipids, of which 50 mol% was a Gd-containing lipid, were incubated with human umbilical vein-derived endothelial cells (HUVECs) for up to 24 h. α(ν) β(3)-integrin targeted (RGD) and non-targeted (NT) pQDs were compared. pQDs uptake was monitored by fluorescence microscopy, FACS, ICP-MS, relaxometry and MRI. Cell-associated pQDs displayed longitudinal relaxation rates and fluorescent intensities which were linear with the cell-associated Gd and Cd concentrations, implying that the Gd and Cd uptake by HUVECs can be quantified using relaxometric and optical measurements, respectively. However, the Gd-to-Cd molar ratio in pellets of pQD-incubated cells was consistently higher than the Gd-to-Cd molar ratio of the pQDs as prepared. It is proposed that this increase in Gd-to-Cd molar ratio was due to non-specific lipid-transfer between the pQDs and the cellular membranes. These findings show that, in the case of contrast agents that are formed by non-covalent interactions, experimental procedures are needed with which representative components of the probes can be monitored.

journal_name

Contrast Media Mol Imaging

journal_title

Contrast media & molecular imaging

authors

Starmans LW,Kok MB,Sanders HM,Zhao Y,Donegá Cde M,Meijerink A,Mulder WJ,Grüll H,Strijkers GJ,Nicolay K

doi

10.1002/cmmi.411

subject

Has Abstract

pub_date

2011-03-01 00:00:00

pages

100-9

issue

eissn

1555-4309

issn

1555-4317

journal_volume

pub_type

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Influence of cell-internalization on relaxometric, optical and compositional properties of targeted paramagnetic quantum dot micelles.