Cationic Surfactant-Induced Formation of Uniform Gold Nanoparticle Clusters with High Efficiency of Photothermal Conversion under Near-Infrared Irradiation

Abstract

A novel and simple method for the fabrication of gold nanoparticle (AuNP) clusters was introduced for use as an efficient near-infrared (NIR) photothermal agent. Cationic surfactants were employed to assemble AuNPs into clusters, during which polyvinylpyrrolidone (PVP) was used to stabilize the AuNP clusters. Through this manner, AuNP clusters with a uniform shape and a narrow size distribution (55.4 ± 5.0 nm by electron microscope) were successfully obtained. A mechanism for the formation of AuNP clusters was studied and proposed. Electrostatic interactions between AuNPs and cationic surfactants, hydrophobic interactions between hydrocarbon chains of cationic surfactants, and repulsive steric interactions of PVP were found to play an important role with regard to the formation mechanism. Photothermal effect in the NIR range of the AuNP clusters was demonstrated; results presented a highly efficient photothermal conversion (with a maximum η of 65%) of the AuNP clusters. The clusters could be easily coated by a silica layer, enabling their biocompatibility and colloidal stability in physiological fluids. The easy-to-fabricate AuNP clusters showed high potential of use as an NIR photothermal agent for cancer therapy.

Gold nanoparticle clusters for the investigation of therapeutic efficiency against prostate cancer under near-infrared irradiation

“…Prior to testing the therapeutic efficacy of the synthesized gold nanoparticle clusters, AuNC@SiO 2 was prepared as described previously [40] and then confirmed using several other methods. Changes in the morphology during conversion from AuNP to AuNC and AuNC@SiO 2 were confirmed through TEM observations as shown in Fig.…”

“…AuNC@SiO 2 was prepared as previously described [40]. Briefly, AuNPs were fabricated via a standard sodium citrate reduction method.…”

“…In this study, we investigated a new photothermal agent that can be used in the treatment of in vitro (Scheme 1) and in vivo cancers. AuNC@ SiO 2 with a diameter of 60-70 nm was synthesized as previously reported [40]. The synthesized AuNC@SiO 2 showed higher photothermal transduction efficiencies of 11.29% to 36.21% over that of single AuNPs.…”

“…This ultimately amplifies the photothermal effect in the NIR region [34][35][36]. Inspired by these interesting properties, gold nanoparticle clusters (AuNCs) can be applied as an efficient photothermal agents [37][38][39][40].…”

“…A method for building AuNPs in cluster form is using a cationic surfactant and biocompatible polymer [40]. In this approach, AuNCs were fabricated via a simple process while maintaining their strong performance as a photothermal agents.…”