Doped ZnO Colloids for Cancer Detection - Bio-Imaging and Cytotoxicity Study
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Doped ZnO Colloids for Cancer Detection - Bio-Imaging and Cytotoxicity Study Linda Y.L. Wu1,2, G.J. Loh3, S. Fu3, A.I.Y. Tok2, X.T. Zeng1, L.C. Kwek3, and F.C.Y. Boey2 1
Singapore Institute of Manufacturing Technology 71 Nanyang Drive, Singapore 638075, e-mail:[email protected] 2 School of Materials Science and Engineering Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 3 National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 ABSTRACT We report the synthesis and surface modification of bio-friendly ZnO based colloids, which have been used for cancer cell detection providing significant advantages on quantum confinement effects, high emission brightness in UV to blue-violate range, non-toxicity and a unique dual color imaging feature. The ZnO nanoparticles were single crystal nanoparticles having spherical shape in size of 1-2 or 4-5 nm depending on the surface capping agents. All the colloidal solutions were stable for 30-45 days. The surface capping is a more effective technique in controlling the nanoparticle size, while dopants are effective in modifying the bandgap and optical properties. Unique dual colour images with blue colour in nucleus and turquoise colour in cytoplasm were obtained using either pure ZnO or Co doped ZnO colloids on human osteosarcoma (Mg-63) cells. The dual colour function is the combined effects of quantum confinement and the bio-compatible surface capping groups. The cytotoxicity study proved no cell proliferation by the nanoparticles up to the concentration of 1000 µg/mL, which is the highest concentration reported so far. Since a dosage of only 50-100µM is enough for the in vivo detection on rate, these ZnO colloids have high potential for use as the detection media for Labon-a-Chip devices. INTRODUCTION Semiconductor quantum dots (QDs) offer high quality optical imaging and various particle-cell immobilization advantages over organic markers [1-3]. The major issue with Cd-containing QDs is the potential cytotoxicity, therefore, alternative materials that do not contain cadmium and are more bio-compatible are required [4]. ZnO is a good candidate due to its biocompatibility and versatile optical properties with a wide bandgap (~3.37eV) and an extremely large exciton binding energy (60 meV), which makes the exciton state stable at room temperature and above. Despite the fact that many synthesis methods for obtaining ZnO nanocrystals in aqueous solution at low temperature have been reported [5-7], the required conditions for bio-imaging are not simultaneously satisfied. Common problems of the existing processes for making ZnO nanocrystals are: high temperature or too fast chemical reaction leading to surface defects (Oxygen or Zinc vacancies) resulting in poor optical properties, no suitable surface capping leading to controlled particle size and shape in aqueous solution, toxic ligands used in the process leading to post treatment and potential contamination/toxicity of the final colloidal
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