Protein-Induced Gold Nanoparticle Assembly for Improving the Photothermal Effect in Cancer Therapy

Gold nanoparticles (AuNPs) are promising photothermal agents for cancer therapy. However, the absorption of spherical AuNPs is weak in the desired tissue-penetrating near-infrared (NIR) window, resulting in low photothermal efficiency within this window. Here, we show that fibrous nanostructures assembled from spherical AuNPs since the templating effect of silk fibroin (SF) could red-shift the optical absorption to NIR and thus present improved photothermal efficiency within the NIR window. Specifically, negatively charged SF, a protein derived from Bombyx mori, was assembled into nanofibers due to the interaction with the positively charged AuNPs and concomitantly templated the AuNPs into fibrous nanostructures. The resultant AuNPs/SF nanofibers presented higher NIR light absorption at 808 nm and higher photothermal efficiency under 808 nm NIR irradiation than nonassembled AuNPs. In vitro and in vivo analyses proved that AuNPs/SF nanofibers could efficiently kill breast cancer cells and destruct breast cancer tumor tissues under one-time NIR irradiation for 6 min by photothermal therapy (PTT) but nonassembled AuNPs could not. This work suggests that the self-assembled AuNPs/SF nanofibers are effective photosensitizers for PTT, and biotemplated assembly of photothermal agents into highly ordered nanostructures is a promising approach to increasing the PTT efficiency.