Abstract—-Semiconductor nanomaterials like TiO 2 nanoparticles (TiO 2 -NPs) approximately less than 100 nm in diameter have become a new generation of advanced materials due to their novel and interesting optical, dielectric, and photo-catalytic properties. With the increasing use of NPs in commerce, to date few studies have investigated the toxicological and environmental effects of NPs. Motivated by the importance of TiO 2 -NPs that may contribute to the cancer research field especially from the treatment prospective together with the fractal analysis technique, we have investigated the effect of TiO 2 -NPs on colony morphology in the dark condition using fractal dimension as a key morphological characterization parameter. The aim of this work is mainly to investigate the cytotoxic effects of TiO 2 -NPs in the dark on the growth of human cervical carcinoma (HeLa) cell colonies from morphological aspect. The in vitro studies were carried out together with the image processing technique and fractal analysis. It was found that, these colonies were abnormal in shape and size. Moreover, the size of the control colonies appeared to be larger than those of the treated group. The mean Df +/- SEM of the colonies in untreated cultures was 1.085±0.019, N= 25, while that of the cultures treated with TiO 2 -NPs was 1.287±0.045. It was found that the circularity of the control group (0.401±0.071) is higher than that of the treated group (0.103±0.042). The same tendency was found in the diameter parameters which are 1161.30±219.56 μm and 852.28±206.50 μm for the control and treated group respectively. Possible explanation of the results was discussed, though more works need to be done in terms of the for mechanism aspects. Finally, our results indicate that fractal dimension can serve as a useful feature, by itself or in conjunction with other shape features, in the classification of cancer colonies. Titiwat Sungkaworn is with the Department of Biology and 6R&D Group of Biological and Environmental physics (BIOPHYSICS), Faculty of Science, Mahidol University, Bangkok 10400, Thailand. Wannapong Triampo is with the Department of Physics and R&D Group of Biological and Environmental Physics (BIOPHYSICS), Department of Physics, Faculty of Science, and Center for Vectors and Vector-Borne Diseases,Mahidol University, Bangkok 10400, Thailand (e- mail:wtriampo@yahoo.com). Pornkamol Nalakarn is with the 5Department of Physics, Faculty of Science & Technology, Thammasat University, and R&D Group of Biological and Environmental Physics (BIOPHYSICS), Faculty of Science, Mahidol University, Bangkok 10400, Thailand. Daraporn Triampo is with the Department of Chemistry and R&D Group of Biological and Environmental Physics (BIOPHYSICS), Faculty of Science, Mahidol University, Bangkok 10400, Thailand. I. Ming Tang is with the Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400, Thailand. Yongwimon Lenbury is with the Department of Mathematics, Faculty of Science, Mahidol University, Bangkok 10400, Thailand. Pontipa Picha is with the National Cancer Institute of Thailand, Bangkok 10400, Thailand. PACS numbers: 85.15.Aa, 87.17. Aa Keywords—Tumor growth, Cell colonies, TiO 2 , Nanoparticles, Fractal, Morphology, Aggregation. I. INTRODUCTION EMICONDUCTOR, nanomaterials like TiO 2 nanoparticles (TiO 2 -NPs), approximately less than 100 nm in diameter, have become a new generation of advanced materials due to their novel and interesting optical, dielectric, and photo-catalytic properties from size quantization [1]. Therefore, many efforts have been devoted to produce TiO 2 - NPs with controlled size, shape, and porosity for use in thin films, ceramics, composites, and catalysts. These nanometer- sized effects are caused by the large surface-to-volume ratio, resulting in more atoms along the grained boundaries than in the bulk material. It is known that the more the particles decrease in size the more attractive interactions between the particles become dominant. These attractive forces lead them to aggregate or agglomerate when the particles collide resulting in nanoparticle aggregates (NPAs) (see Fig. 1). Since the desired product properties might vary with particle size as well as the degree of aggregation or the aggregate structure, control of the particle size distribution and the aggregate structure is a key criterion to product quality. It has been accepted that NPs can exist in two states within a liquid: stable, i.e. particles separate, non-adhering and dispersed, and aggregated or flocculated, i.e. adherent and randomly clumped [2]. This clumping can occur due to van der Waals attractive forces or may be caused by magnetic or other attractions imposed by externally imposed fields. To calculate the particle-particle interaction, the DLVO theory can be employed [3]. Hence, it is very important to realize that the NPs being used in experiments, especially in suspension or colloid form have the properties (e.g., size distribution) which are different from those specified by manufactures. Moreover, in experimental processes such as sonicator, autoclave, pH and so on, may change the state or properties of the particles. Therefore, using NPs in experiments must be done with care. With the increasing use of NPs in commerce, to date few studies have investigated the toxicological and environmental effects of NPs. Exposure to nanoparticle substances can be an important risk factor for human health. The sub-micron size of NPs offers a number of distinct advantages over The Effects of TiO 2 Nanoparticles on Tumor Cell Colonies: Fractal Dimension and Morphological Properties T. Sungkaworn, W. Triampo, P. Nalakarn, D. Triampo, I. M. Tang, Y. Lenbury, and P. Picha S World Academy of Science, Engineering and Technology International Journal of Medical and Health Sciences Vol:2, No:1, 2008 20 International Scholarly and Scientific Research & Innovation 2(1) 2008 ISNI:0000000091950263 Open Science Index, Medical and Health Sciences Vol:2, No:1, 2008 publications.waset.org/11854/pdf