Determination Of The Toxicity Of Quantum Dots With Luminous Bacteria

With the bright fluorescence, narrow emission, broad absorption coefficients,and high photostability, quantumdots (QDs) have received significant attention as potential alternatives to organic dyes during the last decades.However, with the extensive application of quantum dots in the biological fields, it was more accessible for people to contact them. So research concerning the potential toxicity of QDs had also gained a great amount of interest. It was critically important to select QDs with low toxicity in order to realize applications in cellular as well as in vivo labeling. In this paper, a novel method so-called bioluminescence inhibition assay with luminous bacteria (Photobacterium phosphoreum) was introduced to evaluate the toxicity of quantum dots.The main research works are summarized as follows:1.With the mercaptoacetic acid (MAA-), L-cysteine (Cys-),dihydrolipoic acid (DHLA-) and bovine serum albumin (BSA-) as the stabilizers, we prepared CdSe in aqueous phase. And DHLA-CdTe was synthesized under the same synthesis conditions (i.e. reaction temperature, pH, precursor concentration and ratio of Cd2+/Se or Te/ligand).Then the fresh products were dialyzed just before the experiments against ultrapure water to remove the excess ions.While ZAIS QDs were synthesized in organic solution, following water-solubilized with DHLA by a ligand exchange procedure.2.Using the luminous bacteria as a microbial sensing element, we carried out a systematic study on the toxicity of a series of QDs we prepared. Median effective concentration (EC50),the concentration of a compound that inhibits 50% of the bacterial bioluminescence, was chosen as the indication to estimate the toxicity of QDs. These results demonstrated that both composition and surface modification were responsible for the toxicity of QDs. 3.Through UV irradiation experiments,the influence of vitamin C on the toxicity and transmission electron microscopy, the mechanism of toxicity of quantum dots was investigated.4.Bare carbon dots (C-Dots) were prepared of by oxidation of carbon soot with nitric acid refluxing. After surface passivation with polyethylene glycol(PEG1500N), we got the PEG-C-Dots.The toxicity of the two C-Dots was studied based on the bioluminescence inhibition assay with luminous bacteria. Our results demonstrated that the C-Dots were toxic and the surface passivation with PEG reduced the toxicity effectively.