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1、Experimental research on the cytotoxicity of CdSe nanocrystals with the irradiation of violet light Li Chen School of Physics & Optoelectronic Engineering, Guangdong University of Technology Guangzhou, China Jing Zuo, Hua Xiao, Jianwen Xiong School of Physics and Telecommunication Engineering, South
2、 China Normal University Guangzhou, China J AbstractThe present study processed the absorption spectrum of CdSe nanocrystals (Ncs) which was modified by mercaptoacetic acid (MA). Based on this, the LEDs whose emission peak is near the absorption peak of the NCs were selected to form a LED array. Th
3、e leukemia cell line HL60 was cultured in two 96-well plates and incubated with different concentrations of MA-Coated CdSe NCs. One of the 96-well microplates was irradiated by the LED array mentioned above, and the other wasnt. Then the viability of the cells on both microplates was determined usin
4、g CCK-8 assay. The results in vitro demonstrated that the ability of MA-Coated CdSe NCs to induce cell death can be promoted under the irradiation of the light source we used. Keywords-Cadmium selenide (CdSe);violet light;cck-8; cytotoxicity. I. INTRODUCTION Semiconductor nanocrystals, also known as
5、 quantum dots (QDs), are nano-scale inorganic particles in the size range of 1-10nm. Due to their unique and fascinating optical properties resulted from quantum confinement 1, high quality QDs have shown potential applications in biological and biomedical fields, such as clinical diagnostics and ph
6、otodynamic therapy. Photodynamic therapy (PDT) is a technique for cancer therapy. In PDT, light, oxygen and photosensitizing agents are combined to produce a selective therapeutic effect in the target tissue (usually localized tumor). So there exist three key agents that affect the therapeutic effec
7、t, which is light source, photosensitizer, and the concentration of oxygen species. And among these three agents, photosensitizer is the most important one. As its developing, PDT is becoming more and more efficient. However, the application of traditional photosensitizer was restricted because of t
8、heir inherent properties. To solve such issues nanocrystals are currently being explored as potential delivery systems for PDT photosensitizers or directly as PDT agents 2, 3. Since QDs can undergo FRET, they can used to activate other established photosensitizers 3. So far, some researchers have ju
9、st paid attention to explore the possibility of using QDs as photosensitizers in PDT 2. Advances in nanomaterials have led to promising candidates for many biological applications in research and medicine. However, there is a prime issue that hindering the application of QDs in biological and biomed
10、ical fields 4. That is their toxicity 5,6. And fortunately, there has been increasing interest in evaluating the toxicity of them due to the tremendous focus on developing QDs for imaging and therapeutic applications . In this paper, we explored the cytotoxicity of CdSe QDs. The leukemia cell line H
11、L60 was cultured in 96-well microplates and incubated with different concentrations of MA-Coated CdSe QDs. Then the viability of the cells on microplates was determined using CCK-8 assay. To explore the possible application in PDT, the cytotoxicity of CdSe QDs under the irradiation of light was acce
12、ssed. We processed its absorption spectrum. Based on this, the LEDs whose emission peak is near the absorption peak of the NCs were selected to form a LED array. Then we tested the cytotoxicity of HL60 in the same condition except under the irradiation of the LED array mentioned above. The results i
13、n vitro demonstrated that the ability of MA-Coated CdSe QDs to induce cell death can be promoted under the irradiation of the light source we used. II. METHODS AND RESULTS A. QDs cytotoxicity Given the potential for widespread application and commercialization, nanomaterials will be increasingly uti
14、lized for future biological applications. However, some in vitro studies suggest that certain QD types may be cytotoxic and this restrict the use of QDs in biological and biomedical fields. Its known that QDs Quantum dots contain toxic components, they could be released from quantum dots and then ki
15、ll the cells 7, 8. Thus a direct way to avoid the possible toxicity of QDs is to make them well coated by low or nontoxic materials. In general, the toxicity of QDs can be attributed to several factors 9, but for in vivo studies, the main concern is the robustness of the surface coating. And the per
16、vious study also showed that the surface coatings did affect the toxicity of QDs. So although lots of literatures have discussed the cytotoxicity of QDs, yet since each individual type of QDs This work was supported by the Natural Science Foundation of Guangdong Province PRC (Grant No. 7005845 and 8
17、151063101000030). 978-1-4244-4713-8/10/$25.00 2010 IEEEposses its own unique physicochemical properties, which in turn determines its potential toxicity or lack thereof, we assessed the cytotoxicity of QDs used here. Figure1. The OD values of HL60 cultured with QDs of different concentration CdSe QD
18、s which was modified by mercaptoacetic acid (MA) was purchased from JiaYuan Quantum Dot Co., Ltd. Leukemia cell line HL60 were maintained at 37 (5 CO2) in RPMI 1640 medium containing 5 fetal bovine serum. HL60 cells were cultured at 1105 cells per well on two 96-well microplates and incubated with d
19、ifferent concentrations of surface modified CdSe QDs for 12h and 24h respectively. To each well 10l stock CCK-8 was added, then the cells were cultured for 2h at 37. After incubation, we accessed the viability of cells using CCK-8 assay. As shown in Figure1, a dose-dependent decrease in cell viabili
20、ty was observed. Its decreased by increasing the concentrations and incubation time. But the cell viability was all more than 80% when the concentration of QDs was under 12nM. This means that it can be used in biological fields when the concentration is low. The cells treated at the highest concentr
21、ations showed a dramatically decrease in viability compared to controls. Also, we noticed that there are slight decreases of cell viability between 12h and 24h at all concentrations we used, and these decreases indicate an effect of time on cytotoxicity. B. Effect of irradiation on QDs cytotoxicity
22、Due to their unique optical properties, surface modified QDs have been successfully used in biomedical and biological fields. Some researchers have already used the QDs for in vivo biomedical imaging. The literatures cited here demonstrated that surface modified QDs can be used in biological fields
23、without a significant side effect. In vivo studies by Balou and coworkers had confirmed the nontoxic nature of stable protected QDs 10. And our experiment also demonstrated that the QDs we used here showed a little toxic to HL60 cells at low concentration. So its possible that QDs can be used as pho
24、tosensitizers in photodynamic therapy. Bakalova et al explored the feasibility of using QDs as photosensitizers. Also, in Samias work, CdSe QDs were linked to phthalocyanine (Pc4) photosensitizer. They observed Pc4 can be activated by QDs through FRET (fluorescence resonance energy transfer) mechani
25、sm. Its known that the power of PDT lies in its selectivity as it is based on the localized generation of cytotoxic singlet oxygen by light activation of a non-toxic photosensitizer. QDs can transfer absorbed energy to nearby oxygen molecules to generate reactive oxygen species (ROS), the generation
26、 of ROS on the contrary makes quantum dots possible for photodynamic therapy applications 111,12. To probe the possible use of QDs in PDT, we explored the relationship between light irradiation and the cytotoxicity of QDs. The absorption spectrum of QDs was processed in Figur2 using UV-VIS spectrome
27、ter. Based on this, the violet LEDs whose Emission peak is at 403.5nm was selected to form a LED array. The emission spectrum of LED we used was shown in Figure3. Figure2. The absorption spectrum of QDs Figure3. The emission spectrum of LED The cells was treated in the same condition as before, exce
28、pt both microplates was irradiated by the LED array mentioned above for 30 minutes before the CCK-8 regents was added. Then we accessed the viability of cells under the irradiation of violet light using CCK-8 assay. The result was shown in Figure4. 0102030405060708048121620OD value(percent of contro
29、ls)12 hours24 hours Figure4. The OD values of HL60 cultured with QDs of different concentration under the irradiation of violet light The result shown in Figure4 indicates there is still a dose-dependent in cell viability. As the concentration grows the cell viability becoming lower and lower. And c
30、ompared with the result without a violet light irradiation, we noticed a statistically significant decrease of cell viability. This indicates that the ability of MA-Coated CdSe QDs to induce cell death can be promoted by the irradiation of the light source we used. This property makes QDs a novel ca
31、ndidate for photosensitizers. III. CONCLUSION Considering their unique properties of QDs, more and more researchers paid attention to the application in various fields. Yet because of the toxic components, QDs show a toxic effect to cells and this restrict its further application in biological and b
32、iomedical fields. Until the researchers discovered that the cytotoxicity of QDs can be lessened through surface modification, its application in biological becoming more and more popular. In this paper, we explored the cytotoxicity of MA-coated CdSe QDs, the result indicate that there is little toxi
33、c effect on cells at low concentrations. Then we surveyed the cytotoxicity of QDs under the irradiation of violet light, we noticed a higher toxic effect on cell viability. This phenomenon showed a potential use of QDs as photosensitizers in PDT. In our work, we also noticed a dramatically decrease
34、of cell viability when the concentration of QDs is above 12nM, this may be due to the poor protection of mercaptoacetic acid. Maybe a more stable coating layer such as ZnS can solve this problem. And because of the low concentration, the cell viability was higher than we expected after the irradiati
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