Selim et al. Nanoscale Research Letters 2011, 6:528 http://www.nanoscalereslett.com/content/6/1/528 insulin-immobilized CSNPs (ICSNPs) having an average diameter of 13 nm as determined by TEM was narrow. The proliferation of fibroblasts was significantly increased by the presence of ICSNPs. ICSNPs also demonstrated lower cytotoxicity than CSNPs and PCSNPs. The ICSNPs used in this study will have potentials to be used in bio-imaging applications. Additional material Additional file 1: Scheme 1. Schematic diagram showing the preparation of (a) mercaptoacetic acid-coated CSNPS, (b) PCSNPs, (c) ICSNPS and (d) bare CdS. Acknowledgements This work was supported by the Korea Ministry of Education, Science and Technology (contract no. 2009-0073282). Author details 1Department of Polymer Science and Engineering, Kyungpook National University, Daegu 702-701, South Korea 2Medical and Biological Engineering, Kyungpook National University, Daegu 702-701, South Korea 3Department of Diagnostic Radiology, Kyungpook National University, Dongin-dong, Daegu 700-422, South Korea 4College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China Authors’ contributions KMK carried out the preparation and immobilization research work. ZCX and MJC participated in the data processing. YC, HG, IKK participated in the design of the study and performed the statistical analysis. All authors read and approved the final manuscript. Competing interests The authors declare that they have no competing interests. Received: 18 July 2011 Accepted: 23 September 2011 Published: 23 September 2011 References 1. 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