Nabeshi et al. Nanoscale Research Letters 2011, 6:93 http://www.nanoscalereslett.com/content/6/1/93 In this study, the authors demonstrate that surface modification of nSP70 with amine or carboxyl groups alters the intracellular distribution of the nanoparticles and has an effect on cell proliferation. The authors believe that the identification of individual uptake machinery will shed light on the safety of nanosilicas, which are already commercially available in the form of medicines, cosmetics, and foods. Furthermore, it is hoped that analysis of the relationship between surface physicochemical properties and cellular response/distri- bution will help researchers in the development of safer forms of NMs. A safety-prediction as well as safety-eva- luation approach of NMs is an essential prerequisite for maintaining the well-being of the general public. Abbreviations DAPI: 4’,6-diamino-2-phenylindole; NMs: nanomaterials. Acknowledgements The study was also supported in part by the following Research Funding Bodies: Health Labour Sciences Research Grants from the Ministry of Health, Labor and Welfare of Japan; Health Sciences Research Grants for Research on Publicly Essential Drugs and Medical Devices from the Japan Health Sciences Foundation; Global Environment Research Fund from the Minister of the Environment; Knowledge Cluster Initiative; Food Safety Commission; The Nagai Foundation Tokyo; The Cosmetology Research Foundation; The Smoking Research Foundation. Author details 1Department of Toxicology and Safety Science, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565- 0871, Japan. 2Laboratory of Biopharmaceutical Research (Pharmaceutical Proteomics), National Institute of Biomedical Innovation, 7-6-8 Saito-Asagi, Ibaraki, Osaka 567-0085, Japan. 3The Center for Advanced Medical Engineering and Informatics, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan. 4Department of Biomedical Innovation, Graduate School of Pharmaceutical Sciences, Osaka University, 7-6-8, Saito-Asagi, Ibaraki, Osaka 567-0085, Japan. Authors’ contributions HN and T. Yoshikawa designed the study; HN, AA, T. Yoshida, S. Tochigi, TH and TA performed experiments; HN and T. Yoshikawa collected and analysed data; HN and T. Yoshikawa wrote the manuscript; KN, YA, HK, S. Tsunoda, NI and YY gave technical support and conceptual advice. YT supervised the all of projects. 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