Quantifying the Coverage Density of Poly(ethylene glycol) Chains on the Surface of Gold Nanostructures

详细信息    查看全文

• 作者：Xiaohu Xia ; Miaoxin Yang ; Yucai Wang ; Yiqun Zheng ; Qingge Li ; Jingyi Chen ; Younan Xia
• 刊名：ACS Nano
• 出版年：2012
• 出版时间：January 24, 2012
• 年：2012
• 卷：6
• 期：1
• 页码：512-522
• 全文大小：645K
• 年卷期：v.6,no.1(January 24, 2012)
• ISSN：1936-086X

文摘

The coverage density of poly(ethylene glycol) (PEG) is a key parameter in determining the efficiency of PEGylation, a process pivotal to in vivo delivery and targeting of nanomaterials. Here we report four complementary methods for quantifying the coverage density of PEG chains on various types of Au nanostructures by using a model system based on HS鈥揚EG鈥揘H₂ with different molecular weights. Specifically, the methods involve reactions with fluorescamine and ninhydrin, as well as labeling with fluorescein isothiocyanate (FITC) and Cu²⁺ ions. The first two methods use conventional amine assays to measure the number of unreacted HS鈥揚EG鈥揘H₂ molecules left behind in the solution after incubation with the Au nanostructures. The other two methods involve coupling between the terminal 鈭扤H₂ groups of adsorbed 鈭扴鈥揚EG鈥揘H₂ chains and FITC or a ligand for Cu²⁺ ion, and thus pertain to the 鈥渁ctive鈥?鈭扤H₂ groups on the surface of a Au nanostructure. We found that the coverage density decreased as the length of PEG chains increased. A stronger binding affinity of the initial capping ligand to the Au surface tended to reduce the PEGylation efficiency by slowing down the ligand exchange process. For the Au nanostructures and capping ligands we have tested, the PEGylation efficiency decreased in the order of citrate-capped nanoparticles > PVP-capped nanocages 鈮?CTAC-capped nanoparticles CTAB-capped nanorods, where PVP, CTAC, and CTAB stand for poly(vinyl pyrrolidone), cetyltrimethylammonium chloride, and cetyltrimethylammonium bromide, respectively.

Keywords:

Au nanostructure; PEGylation; ligand exchange; capping ligand