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Quantum dots are crystalline semiconductor nanoparticles with unique optical properties due to quantum confinement effects. They have several advantages compared to traditional organic fluorescent dyes, such as high fluorescent brightness, photostability, and tunable emission wavelengths, dependent upon particle size. Their unique optical properties have led to an increased use in a variety of devices, including diode lasers and television displays, as well as in biomedical research. The most commonly used quantum dots (QDs) are made of cadmium selenide (CdSe) and have cadmium selenide core with zinc sulfide shell (CdSe/ZnS), containing inherently toxic cadmium. This work focuses on comparison of the toxic effects of conventional CdSe and CdSe/ZnS QDs and silicon QDs, which are emerging as a potentially benign alternative, using bacteria as model organisms. The bacteria models used for our studies are Shewanella oneidensis MR-1, a Gram-negative bacterium, and Bacillus subtilis SB 491, a Gram-positive bacterium. This research assesses changes in cell viability, respiration pattern, and cell membrane integrity in the presence of the nanoparticles using colony counting, respirometry and membrane integrity assays, respectively. The association of the QDs with bacterial cell membranes was investigated using transmission electron microscopy (TEM). Results indicate that the silicon QDs are benign to the bacteria considered, and they do not associate with the cell membranes. The CdSe cores exhibit significant toxicity to the bacterial cells, whereas the CdSe/ZnS QDs are comparatively less toxic.
Bibliographical noteFunding Information:
This work was supported primarily by the National Science Foundation through the University of Minnesota MRSEC under National Science Foundation Award Number DMR-1420013. Part of this work was carried out in the College of Science and Engineering Characterization Facility, University of Minnesota, which has received capital equipment funding from the NSF through the UMN MRSEC program under Award Number DMR-1420013. SKEH acknowledges support through the NSF Graduate Research Fellowship Program under grant NSF GRFP 00039202. NVH acknowledges support through the National Science Foundation Graduate Research Fellowship Program. V. S. S. K. K. and P. J. B. acknowledge support from Department of Energy under award number DE-SC0001319 JNW acknowledges UMN MRSEC REU Site in Nanomaterials supported through the National Science Foundation MRSEC and REU programs under Award Numbers DMR-1263062 & DMR-1420013. EAM acknowledges Lloyd W. Goerke scholarship and the M. Cannon Sneed Memorial award through the UMN Department of Chemistry. The authors would like to thank Fang Zhou for microtoming the biological TEM samples and Guillermo Marqués and the University Imaging Centers at the University of Minnesota for their help with acquiring fluorescence microscopy images.
© The Royal Society of Chemistry.
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- Period 5