Synthesis of Cadmium Selenide Quantum Dots and Their Cytotoxicity
Cadmium selenide (CdSe) nanoparticles (NPs) have applications in biomedical, biochemistry, bioimaging areas through different methods such as cell labelling and drug delivery (Chapter1). This study aims to test the optical and biological properties of CdSe NPs so that its applications can be improved in these areas in the future. Three types of CdSe NPs have been synthesised using a wet chemical method with the molar ratio of Cd:Se 10:1, 4:1 and 1:1. The observed luminescence of the CdSe NPs was strong and stable. The maxima PL spectrum peak of the CdSe (10:1) nanoparticles was around 590 nm and the ultraviolet-visible absorption (UV-Vis) spectrum showed a peak between 530-550 nm. The photoluminescence peak of CdSe (4:1) was the same as CdSe (10:1) and the UV-Vis spectrum showed a peak at about 550 nm. The aging studies indicate that sodium citrate (a stabiliser) could enhance the stability of the CdSe NPs. For example, the CdSe NPs with 0.2% sodium citrate were more stable than 0.05% (Chapter 3). Using this property, more stable encapsulated drugs could be made in the future to improve the clinical treatment method (Chapter 1). Cell toxicity of the CdSe NPs was evaluated through the use of 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. The MTT results show that the more Cadmium ions accumulated in HHL-5 cells, the greater the cell toxicity is. The results (keeping the cadmium level constant) also indicate that CdSe NPs with a cadmium to selenite ratio with 10:1 (CdSe (10:1) had the strongest toxicity in HHL-5 cell of all these three kinds of CdSe NPs tested. Conversely, the CdSe (1:1) has the lowest toxicity among all. The results indicated that the toxicity of the cadmium were very obvious so that we need to avoid accumulation of cadmium in clinical. In addition, the confocal images in MCF-7 cells also reflect the relative toxicities of the CdSe NPs. The results of the confocal images indicated that the higher concentrations of the CdSe NPs in the cells, the greater the observed toxicity is. Moreover, all the experiments in this study (aging, TEM, quantum yield, MTT, confocal) are surrounding 9 kinds of CdSe NPs without any other parameters, which are novel and unique.
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