Abstract
Indium phosphide quantum dots (QDs) passivated with zinc sulphide in a core/shell architecture (InP/ZnS) with different surface chemistries were introduced to RAW 264.7 murine “macrophage-like” cells to understand their potential toxicities. The InP/ZnS quantum dots were conjugated with an oligonucleotide, a carboxylic acid, or an amino-polyethylene glycol ligand, and cell viability and cell proliferation were investigated via a metabolic assay. Membrane integrity was measured through the production of lactate dehydrogenase. Fluorescence microscopy showed cellular uptake. All quantum dots exhibited cytotoxic behaviour less than that observed from cadmium- or lead-based quantum dots; however, this behaviour was sensitive to the ligands used. In particular, the amino-polyethylene glycol conjugated quantum dots proved to possess the highest cytotoxicity examined here. This provides quantitative evidence that aqueous InP/ZnS quantum dots can offer a safer alternative for bioimaging or in therapeutic applications.
Highlights
Quantum dots (QDs) are semiconductor nanocrystals that show high optical brightness, narrow emission wavelength, and increased photostability compared with organic fluorophores
We demonstrated the modification and characterisation of Indium phosphide (InP)/zinc sulphide (ZnS) QDs with different surface chemistries
This study demonstrated that InP/ZnS QDs with different chemical surfaces (Oligo, polyethylene glycol (PEG)-NH2, and mercaptosuccinic acid (MSA)) have low cytotoxic behaviour after 24 and 48 h exposure, compared with cadmium-based QDs [5]
Summary
Quantum dots (QDs) are semiconductor nanocrystals that show high optical brightness, narrow emission wavelength, and increased photostability compared with organic fluorophores. QDs are considered high-risk respiratory hazards due to their small size, which allows them to reach lung alveoli [6,8] To combat these effects, less toxic semiconductor shells, such as zinc sulphide (ZnS), can be grown on the core QD material, reducing overall cytotoxicity of the particles [9]. The degradation and cytotoxic effects of core/shell QDs can be further reduced by strictly controlling factors such as the size and the surface ligand chemistry of the particles Despite these improvements, there are still widespread concerns over the chronic effects of even statistically minor toxic events over the course of the lifetime of an individual, which significantly reduces the large scale viability of these products [10,11]
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