Dually functionalized dendrimers by temperature-sensitive surface modification and gold nanoparticle loading for biomedical application†
Stimuli-sensitive dendrimers of a new type were developed through dual functionalization of polyamidoamine (PAMAM) dendrimers with temperature-sensitive surface modification using propoxy diethylene glycol (PDEG) and Au nanoparticle (AuNP) loading. These AuNP-hybridized dendrimers were prepared by attaching PDEG to amine-terminated PAMAM G5 dendrimer using 4-nitrophenylchloroformate and subsequent loading of AuNPs into the dendrimer interior via reduction of AuCl4− ions with NaBH4 in the dendrimer interior. Transmission electron microscopy showed that AuNPs with diameters of about 2 nm were retained in the PDEG-modified dendrimers. These AuNP-loaded dendrimers were dissolved in aqueous solutions at low temperature but became water-insoluble above a specific temperature, because of the character change of the dendrimer surface from hydrophilic to hydrophobic depending on temperature. The AuNPs in the dendrimer interior generated heat under irradiation by a green laser and hence, their association could be induced in the specific area irradiated with the green laser. In addition, the combination of the temperature increase and light irradiation was shown to control their interaction with cells, enabling selective cell killing by the AuNP-hybridized temperature-sensitive dendrimers.