title: Quantum dot-insect neuropeptide conjugates for fluorescence imaging, transfection, and nucleus targeting of living cells.
abstract: We identified an insect neuropeptide, namely, allatostatin 1 from Drosophila melanogaster, that transfects living NIH 3T3 and A431 human epidermoid carcinoma cells and transports quantum dots (QDs) inside the cytoplasm and even the nucleus of the cells. QD-conjugated biomolecules are valuable resources for visualizing the structures and functions of biological systems both in vivo and in vitro. Here, we selected allatostatin 1, Ala-Pro-Ser-Gly-Ala-Gln-Arg-Leu-Tyr-Gly-Phe-Gly-Leu-NH2, conjugated to streptavidin-coated CdSe-ZnS QDs. This was followed by investigating the transfection of live mammalian cells with QD-allatostatin conjugates, the transport of QDs by allatostatin inside the nucleus, and the proliferation of cells in the presence of allatostatin. Also, on the basis of dose-dependent proliferation of cells in the presence of allatostatin we identified that allatostatin is not cytotoxic when applied at nanomolar levels. Considering the sequence similarity between the receptors of allatostatin in D. melanogaster and somatostatin/galanin in mammalian cells, we expected interactions and localization of allatostatin to somatostatin/galanin receptors on the membranes of 3T3 and A431 cells. However, with QD conjugation we identified that the peptide was delivered inside the cells and localized mainly to the cytoplasm, microtubules, and nucleus. These results indicate that allatostatin is a promising candidate for high-efficiency cell transfection and nucleus-specific cell labeling. Also, the transport property of allatostatin is promising with respect to label/drug/gene delivery and high contrast imaging of live cells and cell organelles. Another promising application of allatostatin is that the transport of QDs inside the nucleus would lift the limit of general photodynamic therapy to nucleus-specific photodynamic therapy, which is expected to be more efficient than photosensitization at the cell membrane or in the cytoplasm as a result of the short lifetime of singlet oxygen.
authors: Nano-bioanalysis Team and Glycolipid Function Analysis Team, Health Technology Research Center, National Institute of Advanced Industrial Science and Technology, 2217-14 Hayashi-cho, Takamatsu, Kagawa 761-0395, Japan. v.biju@aist.go.jp
authors: Vasudevanpillai
authors: V
authors: Biju
authors: Damodaran
authors: D
authors: Muraleedharan
authors: Ken-ichi
authors: K
authors: Nakayama
authors: Yasuo
authors: Y
authors: Shinohara
authors: Tamitake
authors: T
authors: Itoh
authors: Yoshinobu
authors: Y
authors: Baba
authors: Mitsuru
authors: M
authors: Ishikawa
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000737:chemistry*; D004331:Drosophila melanogaster; D006801:Humans; D007301:Insect Hormones / Q000737:chemistry*; D019476:Insect Proteins / Q000737:chemistry*; D051379:Mice; D009479:Neuropeptides / Q000737:chemistry*; D045663:Quantum Dots; D013050:Spectrometry, Fluorescence / Q000379:methods*; D014162:Transfection
chemical_list: D007301:Insect Hormones; D019476:Insect Proteins; D009479:Neuropeptides; C061164:allatostatin 1