Table 2.

Results for toxicity associated with cadmium quantum dots

QD	Model	Administration	QD concentration	Exposure duration	Toxicity	Ref
CdS-QDs	Soybean plants	Growth medium	50–200 mg/L	14 days	Peroxidases play the predominant role in quenching the oxidative stress caused by CdS-QD exposure. At the highest CdS-QD treatment (200 mg/L), root lignification allowed the plants to restrict Cd accumulation, except in QD-PVP, where lignification was reduced by 21% leading to higher Cd content in shoots	Majumdar et al. 2019
CdSe and CdSe/ZnS	Escherichia coli (E. coli, represents a prokaryotic system) and Phanerochaete chrysosporium (P. chrysosporium, represents eukaryotic system)	In vitro and growth medium	0, 10, 20, 50, and 80 nM	48 h	Bioaccumulation amounts of CdSe QDs by E. coli and P. chrysosporium were larger than those of CdSe/ZnS QDs due to the smaller particle size and less negative surface charges of CdSe QDs.	Hu et al. 2019
CdSe QD, CdSe/ZnS QD	Shewanella oneidensis MR-1	In vitro	A total volume of 150 μL at varying concentrations	15 min	QD interaction leads to membrane disruption, which is mechanical and depends on the QD concentration and their affinity to the liposome membranes	Williams et al. 2018
CdSe/ ZnS	SPF grade female and male BABL/c mice	Subcutaneous injection	5.0, 1.0, and 0.1 pmol/day/mouse	14 days	QDs are found in the ovaries, but no changes are detected on the behavior and estrous cycle on the female mice. The mRNA downregulations of FSHr and LHr are observed, and the number of matured oocytes had shown a significant decrease when the QDs dosage was above 1.0 pmol/day along with a decrease in fertilization rate	Xu et al. 2016
CdSe/ZnS	Human hepatic cell line L02 and 8-week-old male C57BL/6 mice	In vitro (L02), IV injection (mice)	20, 40, and 80 nM (L02) 10 nmol/kg body weight (mice)	48 h (L02) 2 weeks (mice)	CdSe/ZnS QDs conjugated with carboxyl groups induced hepatocyte pyroptosis, and liver inflammation and dysfunction. The in vitro and in vivo hepatic toxicity of QDs was mediated by QDs-induced NLRP3 activation which was attributed to Ca2+ mobilization and mtROS production after exposure to QDs	Lu et al. 2016
CdSe/ZnS	TK6, BEAS-2B, and HFF-1	In vitro	0–20 nM	24 h	Cytotoxicity and genotoxicity are strongly affected by a multitude of parameters including (1) differences in cell type potentially resulting in varying surface area contact with the exposed material, in addition to inherent cellular differences in internalizing NPs and ability to cope with an exogenous insult; (2) the nature of the QD surface chemistry; (3) the degree of QD agglomeration in the presence of varying amounts of serum proteins; (4) differences in cell culture media composition; and (5) time of exposure	Lin et al. 2015
CdSe@MSA and CdSe(S)@MSA QDs	Escherichia coli	In vitro	0–4000 nM	100 min	The toxicity observed for CdSe QDs may be directly linked to •OH radicals produced	Kauffer et al. 2014
TGA/TGH-CdTe	HeLa cells and Kunming mice	In vitro, intravenous injection (in vivo)	In vitro: 45 mg m/L In vivo: 0.4 (low dose), 2.0 (representing medium dose) and 10.0 (representing high dose) mg kg1	24 h	PEG modification played an important role in reducing the toxicity of the QDs. PEG conjugated with the QD surface through chemical bonds and thus altered their surface state. Furthermore, PEG formed a fence-like structure on the QD surface, which could more effectively prevent Cd2+ release, which was induced by the diffusion effect from the QD surface to the solution	Du et al. 2019
GSH-CdQDs and MPA-CdQDs	Lemna minor	Direct exposure	0–15 mg/L	168 h	GSH- and MPA-capped Cd-based QDs have similar toxicity for L. minor but are significantly less toxic than CdCl2	Modlitbová et al. 2018
CdS QDs	Yeast strains	Transcriptomic analysis	0.25 mg/L	24 h	In this case, yeast can be a good model to correlate genes with human orthologues in a cross-species comparison that might help to elucidate the response to toxic insults, like to CdS QDs, at a system level as well as to predict the mode of action of similar compounds in other species	Pasquali et al. 2017
Negatively charged: MPA-CdTe/ZnS QDs, MPA/MPO-CdTe/ZnS QDs, NAC-CdTe/ZnS QDs, GSH-CdTe/ZnS QDs	E. coli	Optical density (OD) assays		2 h	QDs decrease the growth rate of E. coli. The inhibition ratio of positive QDs is higher than that of negative QDs	Lai et al. 2017
Positively charged: CA-CdTe QDs and CA-CdTe/ZnS QDs
CdTe	Liver mitochondria from female Wistar rats	Direct exposure	100 nM	60 min	Two kinds of QDs, coated with MPA and TGA respectively, could impair mitochondrial energy metabolism and affect mitochondrial lipid peroxidation	Xiang et al. 2017
CdTe	Male BALB/c mice	IV injection	High dose of 2.0 nmol per mouse and a low dose of 0.2 nmol per mouse	90 days	Bodyweight measurements demonstrated there was no overt toxicity for both dose at day 90 after exposure, but the high dose CdTe affected body weight up to 15 days after exposure	Lin et al. 2015
CdTe	8-week-old male mice	Intravenous administration	4.125, 8.25, and 16.5 mg/kg	4 weeks	Increased the level of lipid peroxides marker, MDA, in the liver	Zhang et al. 2015a, b
CdTe and CdTe@ZnS QDs	Caenorhabditis elegans	Foraging behavior assay	0.001, 0.01, 0.1, and 1 g/L (CdTe) 0.1 and 1 g/L (CdTe@ZnS QDs)		Neurotoxicity of CdTe QDs at concentrations of 0.1–1 g/L on both the development and function of RMEs motor neurons in nematodes. Data demonstrate the impairment of foraging behavior after CdTe QDs exposure and imply the possible severe ecological risk of long-term exposure to low concentrations of CdTe QDs to environmental animals	Zhang et al. 2015a, b
CdTe	Bombyx mori	IV injection	0.08 nM and 0.32 nM	48 h	Time and dose-dependent damage in the hematopoietic organ and hematocytes. With ROS might be one of the influencing mechanisms	Liu et al. 2014
CdS	Mytilus galloprovincialis	In vitro	0.001, 0.01, 0.1, 1, 10, 25, 50, and 100 mg Cd/L	24 h	CdS QDs exposures decreased the cell viability of both hemocytes and gill cells. Main mechanisms of toxicity of CdS QDs in mussel hemocytes and gill cells involve ROS production and genotoxicity	Katsumiti et al. 2014
Phospholipid micelle encapsulated CdSe/CdS/ZnS QDs	Kunming mice	IV injection	0.81 mg (7.2 μmol)/kg	14 days	QD exposure with a short buffering period before conception does not cause overt pregnancy complications or significant toxicity effects	Xiang et al. 2017