Dendrimer‐Stabilized Gold Nanoflowers Embedded with Ultrasmall Iron Oxide Nanoparticles for Multimode Imaging–Guided Combination Therapy of Tumors

Abstract

Development of multifunctional theranostic nanoplatforms with improved diagnostic sensitivity and therapeutic efficiency of tumors still remains a great challenge. A unique multifunctional theranostic nanoplatform based on generation 5 (G5) poly(amidoamine) dendrimer–stabilized gold nanoflowers (NFs) embedded with ultrasmall iron oxide (USIO) nanoparticles (NPs) for multimode T 1‐weighted magnetic resonance (MR)/computed tomography (CT)/photoacoustic (PA) imaging–guided combination photothermal therapy (PTT) and radiotherapy (RT) of tumors is reported here. G5 dendrimer–stabilized Au NPs and citric acid–stabilized USIO NPs are separately prepared, the two particles under a certain Fe/Au molar ratio are mixed to form complexes, the complexes are exposed to Au growth solution to form NFs via a seed–mediated manner, and the remaining dendrimer terminal amines are acetylated. The formed dendrimer‐stabilized Fe3O4/Au NFs (for short, Fe3O4/Au DSNFs) have a mean diameter of 99.8 nm, display good colloidal stability and cytocompatibility, and exhibit a near‐infrared absorption feature. The unique structure and composition of the Fe3O4/Au DSNFs endows them with a high r 1 relaxivity (3.22 mM−1 s−1) and photothermal conversion efficiency (82.7%), affording their uses as a theranostic nanoplatform for multimode MR/CT/PA imaging and combination PTT/RT of tumors with improved therapeutic efficacy, which is important for translational nanomedicine applications.

Dendrimer‐Based Gold Nanostructures for SERS Detection of Pesticides in Water

“…Interestingly, the magnitude of the red shift in the LSPR for nanoflowers prepared from similar Au cores, depends on the type of terminal groups present in the PAMAM; for the amine terminated dendrimer, a 95 nm shift was observed while a 55 nm red shift was observed for the carboxylic terminated dendrimer (Figure ). It has been suggested before that the nature of the PAMAM dendrimer terminal groups have strong influence in the coordination nature of the Au(III) precursors, which subsequently affect the particle growth via seeded‐growth mechanism , , , . We suggest here that PAMAM dendrimer molecules covering the surface of the seed particles also influence the clustering and growth of the particles.…”

“…shows the 1 H NMR spectrum of Au DSNP prepared in the presence of PAMAM dendrimers with the amine end groups. The 1 H NMR data show the expected peaks for the PAMAM dendrimers (2–4 ppm) confirming their presence as stabilizers of the Au colloids , . The signal of the methylene protons (‐CH 2 ‐) from the ethylenediamine (EDA) core are more difficult to observe given their inferior number of protons when compared with the equivalent moieties of the branching units/terminal groups.…”

“…The characteristic localized surface plasmon resonance (LSPR) band of Au is peaked at 525, 620 and 580 nm respectively for the colloidal samples DSNP, DSNF ‐NH 2 and DSNF ‐COOH. The red shift observed in the LSPR from sample DSNP, which were used as seeds into the growing of both DSNF systems, has been ascribed to the formation of anisotropic Au nanoparticles , . The observed gradual change in the colour of the colloids, from red to blue, is indicative of the complete depletion of the limiting reactant (Au(III) precursor) followed by the favourable formation of bigger clusters that result in the anisotropic growth of the seed particles.…”

“…On the other hand, the carboxylic and amine terminal groups of PAMAM dendrimers can be used to promote the reduction of a metal salt, thus originating dendrimer stabilized metal nanoparticles (DSNP). It turns out that the DSNP can be used as seeds to grow other type of metal nanostructures, such as anisotropic dendrimer stabilized nanoflowers (DSNF) . Figure shows the optical absorption spectra of Au DSNP and Au DSNF colloids prepared by using these strategies.…”

“…Moreover, by the selective change of the surface chemistry of PAMAM dendrimers, the colloidal stability of nanoparticles under variable chemical conditions can be improved. The characteristic surface chemistry along with well‐defined size of PAMAM dendrimers can also be further explored for the blending of more complex systems, which can deliver multifunctionality to the final material …”