| Quantum dots (QDs) have gained significant attention due to their superior opticalproperties and wide usage in biological and biomedical studies. In recent years, therehas been intense concern regarding the in vivo biological safety of QDs. Heave metalions-containing QDs can kill cells in culture by producing ROS. Comparatively, thereare a few comprehensive in vivo behavior and toxicity studies in animals and the resultsare often contrary to those obtained in cell culture studies. The invertebrate modelorganism, Bombyx mori, was selected to determine the effect of water-soluble CdTequantum dots (CdTe QDs) with two sizes on hematopoietic tissues and the functions bybiological detection, microscope, apoptosis detection and in vitro organ culture ofhematopoietic. We also explored the mechanisms of apoptosis and the damage tohematopoiesis after QDs exposure. The results are as follows:1. Water-soluble CdTe QDs inhibit growth and cause deathin B. mori.At an early stage, lethal toxicity studies were performed in5th instar larvae byexposing to QDs for48h, and the results showed that LC50values were8.0μmol/LQDs530and34.5μmol/L QDs720at60h after exposure, respectively. The larvae wereexposed to two doses of QDs530/QDs720,0.08nΜ/larva (8μmol/L,10μL) and0.32nΜ/larva (32μmol/L,10μL), respectively. The results slowed that the explosure ofQDs530/QDs720slows down the growth of larvae and raise the death rate. QDs530with a smaller particle size had a greater toxicity impact.2. Water-soluble CdTe QDs entered the circulating hemocytes and theninduced apoptosis of hemocytes in B. mori.Targeting hemocytes in the circulating hemolymph, the invasion process of twosizes CdTe QDs into various types of hemocytes and the resulting damage in these cellswere investigated. The potential toxicity of QDs on the organisms was evaluated.SingleCys exhibited strong phagocytosis of QDs530. QDs530aggregated in hemocytes or were degraded, caused obvious deformity, apoptosis/necrosis of the cells and resultedin large quantities of cell fragments. QDs720, with a larger particle size, were firstencapsulated by several hemocytes and then phagocytosis occurred. After phagocytosis,QDs720finally aggregated in a single or several cells, and hemagglutination occurred.Besides, the number and kinds of circulating hemocytes varied significantly in theQDs-treated group compared with that in the control group.The relationship between cell apoptosis and QDs invasion was further assessedusing PI staining after considered the other options. Nuclear division and damage tohemocytes were detected using DAPI. The number of dead cells (stained red by PI)significantly increased after exposure to QDs530in a time with a dose-dependentmanner. DAPI staining clearly showed that Pro underwent nuclear fragmentation afterexposure to QDs. In addition, mitosis was observed in Pro. Besides, damagedhemocytes including Pro, QDs stimulated the division of Pro and hence hematopoiesis.3. Water-soluble CdTe QDs inhibited hematopoiesis in B. mori.To analysis the effects of QDs on hematopoiesisin hematopoietic organs, thehanging drop technique was employed to culture HOs. The growth and hemocytesecretion of HOs were investigated. The results showed the growth of HOs afterexposure to QDs. Atrophy or even necrosis of HOs was observed in an apparentdose-dependent manner. The more delayed the HO was separated from the QDsexposure in vivo, the greater the adverse impact would be. HOs underwent obvioushematopoietic recovery in vitro after being removed from QDs exposure in vivo.Recovery of the QDs720group took less time than that in the QDs530group with abetter recovery effect.4. Preliminary study on the injury and repair mechanisms of hematopoiesisafter Water-soluble CdTe QDs exposure.After preliminary test the transcriptional level change of programmed celldeathassociated gene and ROS level, we studied the injury and repair mechanisms inhematopoietic organs. In the present study, a large amount of ROS was induced by QDsexposure in the HO before hematopoiesis was seriously impacted. During the process ofgrowth and recovery of hematopoiesis in the HO, ROS in the tissues were reduced to anormal level. ROS caused by QDs exposure may be responsible for the retarded growthof HOs and hematopoiesis impairment. O2-remained unchanged, which was speculatedthat there might be influencing mechanisms other than ROS with respect to the growth and hematopoiesis of HOs after exposure to QDs. The transcriptional level change ofDroncwave motion, Atg6and Atg8gene was increased, which showed that theautophagy and apoptosis in hematopoietic organ srelated to programmed cell death.These findings suggested that the effects of water-soluble CdTe QDs on growth,hemocytes and hematopoiesis in B. mori and the effects were typically dose-andsize-dependent. In our opinion, these findings provide reliable date to study the toxicityand applications of water-soluble QDs such as biomaterials. |
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