Abstract
This study examines dose effects of cadmium telluride quantum dots (CdTe-QDs) from two commercial sources on model macrophages (J774A.1) and colonic epithelial cells (HT29). Effects on cellular immune signalling responses were measured following sequential exposure to QDs and Pseudomonas aeruginosa strain PA01. At CdTe-QD concentrations between 10(-2) and 10 µg/ml, cells exhibited changes in metabolism and morphology. Confocal imaging revealed QD internalisation and changes in cell-cell contacts, shapes and internal organisations. QD doses below 10(-2) µg/ml caused no observed effects. When QD exposures at 10(-7) to 10(-3) µg/ml preceded PA01 (10(7) bacteria/ml) challenges, there were elevated cytotoxicity (5-22%, p < 0.05) and reduced levels (two- to fivefold, p < 0.001) of nitric oxide (NO), TNF-α, KC/CXC-1 and IL-8, compared with PA01 exposures alone. These results demonstrate that exposures to sub-toxic levels of CdTe-QDs can depress cell immune-defence functions, which if occurred in vivo would likely interfere with normal neutrophil recruitment for defence against bacteria.