Preparation of PEG-modified PAMAM dendrimers having a gold nanorod core and their application to photothermal therapy

A new type of hybrid dendrimer consisting of a gold nanorod core and polyethylene glycol-modified polyamidoamine dendrons was developed for biomedical applications such as photothermal therapy.

PEGylated inorganic nanoparticles

Application of inorganic nanoparticles in diagnosis and therapy has become a critical component in the targeted treatment of diseases. The surface modification of inorganic oxides is important for providing diversity in size, shape, solubility, long-term stability, and attachment of selective functional groups. This Minireview describes the role of polyethylene glycol (PEG) in the surface modification of oxides and focuses on their biomedical applications. Such a PEGylation of surfaces provides "stealth" characteristics to nanomaterials otherwise identified as foreign materials by human body. The role of PEG as structure-directing agent in synthesis of oxides is also presented.

Effective tolerance to serum proteins of head-tail type polycation vectors by PEGylation at the periphery of the head block

To improve the stability of a head-tail type polycation (PAMAM dendron-PLL), which is composed of a polyamidoamine (PAMAM) dendron head and poly(l-lysine) (PLL) tail blocks, as a gene vector against serum proteins, the PEGylation of the PAMAM dendron head was examined using physicochemical and transfection experiments. The PEGylation of the PAMAM dendron-PLL polyplexes neutralized the zeta-potential, indicating that the PEG brushes surround the surface of the polyplexes. The PEGylated PAMAM dendron-PLL polyplexes had higher tolerance against incubation with serum proteins when compared with non-PEGylated PAMAM dendron-PLL polyplexes. In addition, the transfection efficiency of the PEGylated PAMAM dendron-PLL polyplexes increased with increasing incubation periods, leading to an increase in the amount of pDNA uptaked by HeLa cells. Furthermore, effective stabilization of the PAMAM dendron-PLL polyplexes through PEGylation of the PAMAM dendron block was confirmed by the transfection experiments after preincubation with serum proteins and the PEGylated PAMAM dendron-PLL polyplexes showed a comparable level of transfection efficiency with polyethyleneimine polyplexes.

X-ray computed tomography contrast agents prepared by seeded growth of gold nanoparticles in PEGylated dendrimer

Gold nanoparticles (Au NPs) are a potential x-ray computed tomography (CT) contrast agent. A biocompatible and bioinactive surface is necessary for application of gold nanoparticle to CT imaging. Polyethylene glycol (PEG)-attached dendrimers have been used as a drug carrier with long blood circulation. In this study, the Au NPs were grown in the PEGylated dendrimer to produce a CT contrast agent. The Au NPs were grown by adding gold ions and ascorbic acid at various equivalents to the Au NP-encapsulated dendrimer solution. Both size and surface plasmon absorption of the grown Au NPs increased with adding a large number of gold ions. The x-ray attenuation of the Au NPs also increased after the seeded growth. The Au NPs grown in the PEG-attached dendrimer at the maximum under our conditions exhibited a similar CT value to a commercial iodine agent, iopamidol, in vitro. The Au NP-loaded PEGylated dendrimer and iopamidol were injected into mice and CT images were obtained at different times. The Au NP-loaded PEGylated dendrimer achieved a blood pool imaging, which was greater than a commercial iodine agent. Even though iopamidol was excreted rapidly, the PEGylated dendrimer loading the grown Au NP was accumulated in the liver.