Linker-free Gold Nanoparticle Superstructure Coated with Poly(dopamine) by Site-Specific Polymerization for Amplifying Photothermal Cancer Therapy

Although linker-free Au nanoparticle superstructures (AuNPSTs) have demonstrated to have satisfactory photothermal conversion efficiency owing to their enhanced visible-near-infrared absorption caused by the interparticle coupling, they cannot be used directly for in vivo photothermal therapy (PTT) of cancer because of poor stability. To address this issue, we herein propose a polymer-coating strategy, dressing AuNPST on a poly(dopamine) (PDA) coat, and successfully investigate the in vivo PTT effect of AuNPSTs. By employing Triton X-100 as an emulsifier for the formation of AuNPSTs, dopamine was site-specifically polymerized around each AuNPST by the interaction between -OH of Triton X-100 and -NH2 of dopamine. As-fabricated AuNPST/PDA has a sphere-like shape with an average diameter of ~106 nm and the PDA shell is about 10 nm PDA thick. The AuNPST/PDA shows enhanced durability to heat, acid, and alkali compared with bare AuNPST. Also, under 808 nm laser irradiation, AuNPST/PDA shows photothermal conversion efficiency of ~33%, higher than bare AuNPST (~23%). Significantly, AuNPST/PDA can be used as in-vitro and in-vivo PTT agent and shows excellent therapeutic efficacy for tumor ablation thanks to its enhanced stability and biocompatibility, indicative of its potential practicability in clinical PTT.

Keywords: Au nanoparticle; photothermal therapy; poly(dopamine); site-specific polymerization; superstructure.