Redesign of hydrophobic quantum dots mitigates ligand-dependent toxicity in the nematode C. elegans

Niemuth, N. J.; Cui, Y.; Williams, D. N.; Klaper, R. D.; Rosenzweig, Z.; Orr, G.; Mensch, Arielle

Redesign of hydrophobic quantum dots mitigates ligand-dependent toxicity in the nematode C. elegans

Abstract

Surface properties of engineered nanomaterials (ENMs) have been shown to influence their interaction with biological systems. However, studies to date have largely focused on hydrophilic materials, likely due to biocompatibility concerns and aqueous exposure conditions necessary for many model systems. Therefore, a knowledge gap exists in nanotoxicity literature for impacts of hydrophobic ENMs, with studies of hydrophobic materials largely limited to carbon ENMs. Here we demonstrate testing of hydrophobic quantum dots (QDs) using the nematode C. elegans, a model soil organism cultured on solid media and amenable to hydrophobic exposures. To evaluate the influence of hydrophobicity, we compared CdSe/ZnS QDs functionalized with hydrophobic trioctylphosphine oxide (TOPO) to identical QDs functionalized with hydrophilic dihydrolipoic acidpolyethylene glycol (DHLA-PEG) and alternative hydrophobic CdSe/ZnS QDs functionalized with oleic acid (OA). Results show that hydrophobic TOPO QDs are significantly more toxic than hydrophilic DHLA-PEG QDs, and substitution of TOPO with OA yields relatively non-toxic hydrophobic QDs. Fluorescence microscopy shows TOPO QDs loosely associated with the organism's cuticle, but atomic force microscopy shows no difference in cuticle structure from exposure. Importantly, TOPO ligand alone is as toxic as TOPO QDs, and our data suggests that TOPO may impact neuromuscular function, perhaps upon displacement from the QD surface. This study demonstrates the importance of examining ligand-specific impacts of hydrophobic ENMs and indicates OAfunctionalized QDs as a potential alternative to TOPO QDs for reduced toxicity.

Title	Redesign of hydrophobic quantum dots mitigates ligand-dependent toxicity in the nematode C. elegans
Creator	Niemuth, N. J.
	Cui, Y.
	Williams, D. N.
	Klaper, R. D.
	Rosenzweig, Z.
	Orr, G.
	Mensch, Arielle
Publisher	Nanoimpact
Academic Department	Chemistry
Division	Natural Sciences
Organization	Lafayette College
Date Issued	April 2021
Date Available	2022-12-14
Type	Article
Language	English
Keyword	Oleic acid
	Quantum dot
	Hydrophobic
	C. elegans
	Nanotoxicity
	Trioctylphosphine oxide
Bibliographic Citation	Niemuth, N. J., et al. (2021 Apr) "Redesign of hydrophobic quantum dots mitigates ligand-dependent toxicity in the nematode C. elegans." Nanoimpact 22: 100318.
Standard Identifier	DOI 10.1016/j.impact.2021.100318
Standard Identifier	Handle 10385/t722hb259
Permalink	http://hdl.handle.net/10385/t722hb259
Rights Statement	In Copyright
Rights Holders	Elsevier, Ltd.