Evaluation of quantum dot cytotoxicity: interpretation of nanoparticle concentrations versus intracellular nanoparticle numbers

Abstract

While substantial progress has been achieved in the design of more biocompatible nanoparticles (NP), detailed data are required on the precise interactions of NPs and their environment for more reliable interpretation of toxicity results. Therefore, this study aims to investigate the interaction of two quantum dots (QDs) of the same core material CdSe/ZnS coated with two different amphiphilic polymers, with two well-established mammalian cell lines representing possible sites of QD accumulation. Results are linked to either extracellular QD concentrations (given dose) or cellular QD levels (number of internalized particles). In this study, QD internalization, effects on cellular homeostasis, and consequent inflammatory and cytoskeletal alterations caused by these QDs were explored. Fluorescence imaging techniques, including; image-based flow cytometry, confocal microscopy and high-content imaging with the InCell analyzer were used in a multiparametric methodology to evaluate cell viability, induction of oxidative stress, mitochondrial health, cell cytoskeletal functionality and changes in cellular morphology. Gene expression arrays were also carried out on 168 key genes involved in the cytoskeletal architecture and inflammatory pathway accompanied with the analysis of focal adhesions as key markers for actin-mediated signaling. Our results show distinct differences between the PMA and PTMAEMA-stat-PLMA coated QDs, which could mainly be attributed to differences in their cellular uptake levels. The toxicity profiles of both QD types changed drastically depending on whether effects were expressed in terms of given dose or internalized particles. Both QDs triggered alterations to important but different genes, most remarkably the up-regulation of tumor suppression and necrosis genes and the down regulation of angiogenesis and metastasis genes at sub-cytotoxic concentrations of these QDs.

Keywords:

• Cellular uptake
• polymer coating
• quantum dot
• toxicity

Acknowledgments

The authors are grateful to Dr. Christian Geidel for polymer synthesis in the exploratory stage of this project.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

This work was supported by the FWO-Vlaanderen (SJS and KAN 1514716N to BBM), Flemish agency for Innovation by Science and Technology (IWT SBO MIRIAD/130065 and NanoCoMIT/140061) and the KU Leuven program financing IMIR (PF 2010/017). Beatriz Pelaz acknowledges a Post Doctoral fellowship from the Alexander von Humboldt Foundation. Parts of this project were funded by the European Commission (grant FutureNanoNeeds to WJP). The authors are responsible for writing of the article and report no conflicts of financial, consulting, and personal interests.

Supplementary material available online