482
Bioconjugate Chem. 2004, 15, 482−490
Cellular Trajectories of Peptide-Modified Gold Particle Complexes: Comparison of Nuclear Localization Signals and Peptide Transduction Domains Alexander G. Tkachenko, Huan Xie, Yanli Liu, Donna Coleman, Joseph Ryan, Wilhelm R. Glomm, Mathew K. Shipton, Stefan Franzen,* and Daniel L. Feldheim* Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695. Received October 14, 2003; Revised Manuscript Received February 28, 2004
Gold nanoparticles modified with nuclear localization peptides were synthesized and evaluated for their subcellular distribution in HeLa human cervical epithelium cells, 3T3/NIH murine fibroblastoma cells, and HepG2 human hepatocarcinoma cells. Video-enhanced color differential interference contrast microscopy and transmission electron microscopy indicated that transport of nanoparticles into the cytoplasm and nucleus depends on peptide sequence and cell line. Recently, the ability of certain peptides, called protein transduction domains (PTDs), to transclocate cell and nuclear membranes in a receptor- and temperature-independent manner has been questioned (see for example, Lundberg, M.; Wikstrom, S.; Johansson, M. (2003) Mol. Ther. 8, 143-150). We have evaluated the cellular trajectory of gold nanoparticles carrying the PTD from HIV Tat protein. Our observations were that (1) the conjugates did not enter the nucleus of 3T3/NIH or HepG2 cells, and (2) cellular uptake of Tat PTD peptide-gold nanoparticle conjugates was temperature dependent, suggesting an endosomal pathway of uptake. Gold nanoparticles modified with the adenovirus nuclear localization signal and the integrin binding domain also entered cells via an energy-dependent mechanism, but in contrast to the Tat PTD, these signals triggered nuclear uptake of nanoparticles in HeLa and HepG2 cell lines.
INTRODUCTION
The diagnosis and treatment of disease at the cellular level would be greatly enhanced by the ability to deliver analyte probes and therapeutic agents into specific cells and cellular compartments. The nucleus is the desired target for cancer therapies that involve DNA-drug interactions, genes, short interfering RNA, and antisense strategies that target RNA splicing. These therapeutic agents are often prevented from reaching the cell nucleus because of size, charge, or, in the case of small molecules, because P-glycoproteins pump them out of the cell. Vectors that cross cell and nuclear membrane barriers efficiently and are unaffected by cellular pumping mechanisms could aid in the implementation of many novel disease treatments. Targeted nuclear delivery is a challenging task, however, as any cell-specific nuclear probe must satisfy the following requirements: it must (i) be small enough to enter cells and cross the nuclear membrane (
