RNAi的機制之中，siRNA可以用來抑制目標基因的表現。RNAi也在近年來迅速成為功能性調節基因的工具，並且在基因治療的應用上佔有重要的地位。然而利用siRNA作為基因抑制的成功關鍵，便是在於其能否有效的傳送到細胞內。因此，安全並且有效的siRNA傳輸系統是現在迫切需要的。
在本實驗中，我們合成4.5nm的正電荷金奈米粒子，表面以thiocholine包覆。此材料展現出與siRNA很好的結合能力，並且能夠中和siRNA的電性。作為一個siRNA的載體，金奈米粒子對於siRNA擁有很好的保護能力。我們同時也發現siRNA的釋放與PH值有很大的關係，因此我們可以預測我們的材料在細胞內的siRNA釋放的情況。我們也研究金奈米粒子在不同濃度與不同回復時間之下對於細胞的毒性極低。我們結論是表面修飾有thiocholine的金奈米粒子擁有對siRNA良好的保護能力，並在做為基因載體上有很大的潛力。

Short interfering RNA (siRNA) can be used to regulate expression of the targeted gene functionalized as RNA interference (RNAi). RNAi has rapidly become a popular tool for functional genomics research and target gene validation, and holds great promise for therapeutic applications as well. However, the successibility of gene silencing applications based on the use of synthetic siRNA depends on the probability of delivery system. Therefore, the development of save and efficient siRNA delivery systems is of urgent.
In this study, we synthesized 4.5 nm gold nanoparticles (AuNPs) with positive charge by coating with thiocholine capped groups. The AuNPs exhibited good capacity in forming of Au-siRNA complex by neutralizing the surface charge of siRNA. As a siRNA carrier, AuNPs performed distinguishable ability in siRNA protection. We also show that the release of siRNA on gold nanoparticles is response to pH, so we can predict the release condition of siRNA in cells. We have investigated the cytotoxicity of Gold nanoparticles at different concentrations and recover times, and the results show that gold nanporticles are nontoxic to living cells. In conclusion, thiocholine capped gold nanoparticles show good ability to protect siRNA and have capability for gene delivery.

(1) (a) Alivisatos, P. Nat. Biotechnol. 2004, 22, 47. (b) West, J. L.; Halas,
N. J. Curr. Opin. Biotechnol. 2000, 11, 215. (c) Parak, W. J.; Gerion,
D.; Pellegrino, T.; Zanchet, D.; Micheel, C.; Williams, S. C.;
Boudreau, R.; Le Gros, M. A.; Larabell, C. A.; Alivisatos, A. P.
Nanotechnology 2003, 14, R15. (d) Chan, W. C. W.; Maxwell, D. J.;
Gao, X.; Bailey, R. E.; Han, M.; Nie, S. Curr. Opin. Biotechnol.
2002, 13, 40. (e) Drummund, T. G.; Hill, M. G.; Barton, J. K. Nat.
Biotechnol. 2003, 21, 1192. (f) Willner, I.; Patolsky, F.; Weizmann,
Y.; Willner, B. Talanta 2002, 56, 847. (g) Niemeyer, C. M. Angew.
Chem., Int. Ed. 2001, 40, 4128.
(2) Astruc, D.; Daniel, M.-C. Chem. Rev. 2004, 104, 293.
(3) Fire, A. ; Xu, S. Q.; Montgomery, M. K.; Kostas, S. A.; Driver, S. E.;
Mello, C. C. Nature 1998, 391, 806.
(4) (a) Andres, R. P.; Bein, T.; Dorogi, M.; Feng, S.; Jenderson, J. I.;
Kubiak, C. P.; Mahoney, W.; Osifchin, R. G.; Reifenverger, R.
Science 1996, 272, 1323. (b) Toshima, N.; Yonezawa, T. Bimetallic
New J. Chem. 1998, 1179. (c) Fendler, J. H. Chem. Mater. 1996, 8,
1616.(d) Henglein, A. J. Phys. Chem. 1993, 97, 5457. (e) Belloni, J.
Curr. Opin. Colloid Interface Sci. 1996, 1, 184.
(5) Alivisatos, A. P. Science 1996, 271, 933.
(6) Turkevitch, J.; Stevenson, P. C.; Hillier, J. Faraday Soc. 1951, 11, 55.
(7) Yonezawa, T.; Kunitake, T. Colloids Surf. A: Physicochem. Eng. Asp.
1999, 149, 193.
(8) Elghanian, R.; Storhoff, J. J.; Mucic, R. C.; Letsinger, R. L.; Mirkin,
C. A. Science 1997, 277,1078.
(9) (a) Williams, D. A.; Baum, C. Science 2003, 302, 400. (b)
Cavazzana-Calvo M.; Thrasher A.; Mavilio F. Nature 2004, 427, 779.
(10) Verma, I. M.; Somia, N. Nature 1997, 389, 239.
(11) Luo, D.; Saltzman, M. W. Nature Biotechnol. 2000, 18, 33
(12) (a) Boyce, N. Nature 2001, 414, 677. (b) Check, N. Nature 2002,
420, 116.
(13) (a) Hamilton, A. J.; Baulcom, D. C. Science 1999, 286, 950. (b)
Bernstein, E. et al. Nature 2001, 409, 363.
(14) Brummelkamp, T. R. et al. Science 2002, 296, 550.
(15) Zhou, J.; Wu, J.; Hafdi, N.; Peng, L. Chem. Commun., 2006, 7, 2362
(16) Niidome, T. Chem. Commun., 2004, 5, 1978.
(17) Kawano, T.; Niidome, Y.; Katayama, Y.; Niidome, T. Molecular
Therapy 2005, 11, S84
(18) Choi, J. S.; Lee, E. J.; Jang, H. S.; Park, J. S. Bioconjugate Chem.;
2001, 12, 108.