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Endocytosis and lack of cytotoxicity of alkyl–capped silicon quantum dots prepared from porous silicon

Lookup NU author(s): Wi Phatvej, Dr Harish Datta, Dr Simon Wilkinson, Dr Elaine Mutch, Professor Ann DalyORCiD, Dr Ben Horrocks

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

Freely-dissolved silicon quantum dots were prepared by thermal hydrosilation of 1-undecene at high-porosity porous silicon under reflux in toluene. This reaction produces a suspension of alkyl-capped silicon quantum dots (alkyl SiQDs) with bright orange luminescence, a core Si nanocrystal diameter of about 2.5 nm and a total particle diameter of about 5 nm. Previous work has shown that these particles are rapidly endocytosed by malignant cell lines and have little or no acute toxicity as judged by the standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for viability and the Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay for apoptosis. We have extended this work to the CACO-2 cell line, an established model for the human small intestinal mucosa, and demonstrate that neither acute nor chronic (14 days) toxicity is observed as judged by cell morphology, viability, ATP production, ROS production and DNA damage (single cell gel electrophoresis) at doses of 50–200 μg mL−1. Quantitative assessment of the extent of uptake of alkyl SiQDs by CACO-2, HeLa, HepG2, and Huh7 cell lines by flow cytometry showed a wide variation. The liver cell lines (HepG2 and Huh7) were the most active and HeLa and CACO-2 showed comparable activity. Previous work has reported a cholesterol-sensitivity of the endocytosis (HeLa), which suggests a caveolin-mediated pathway. However, gene expression analysis by quantitative real–time polymerase chain reaction (RT-PCR) indicates very low levels of caveolins 1 and 2 in HepG2 and much higher levels in HeLa. The data suggest that the mechanism of endocytosis of the alkyl SiQDs is cell-line dependent.

Publication metadata

Author(s): Phatvej W, Datta HK, Wilkinson SC, Mutch E, Daly AK, Horrocks BR

Publication type: Article

Publication status: Published

Journal: Materials

Year: 2019

Volume: 12

Issue: 10

Online publication date: 25/05/2019

Acceptance date: 19/05/2019

Date deposited: 03/06/2019

ISSN (electronic): 1996-1944

Publisher: MDPIAG

URL: https://doi.org/10.3390/ma12101702

DOI: 10.3390/ma12101702

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