Comparative hyperthermia effects of silica–gold nanoshells with different surface coverage of gold clusters on epithelial tumor cells

Silica-gold nanoshell (SGNS), which is a silica core surrounded by a gold layer, was synthesized by seed-mediated coalescence of gold clusters in an electroless plating solution. SGNS variations with different surface coverage of gold clusters were prepared by adjusting the amounts of gold salts in the presence of formaldehyde-reducing agents. Fully covered SGNS (f-SGNS) with connected gold clusters exhibited stronger intensity and more redshift of plasmon bands located around 820 nm than those of partially covered SGNS (p-SGNS) with disconnected gold clusters. Upon irradiation with near-infrared light (30 W/cm(2), 700-800 nm), f-SGNS caused a larger hyperthermia effect, generating a large temperature change (ΔT =42°C), as compared to the relatively small temperature change (ΔT =24°C) caused by p-SGNS. The therapeutic antibody, Erbitux™ (ERB), was further conjugated to SGNS for specific tumor cell targeting. The f-ERB-SGNS showed excellent therapeutic efficacy based on the combined effect of both the therapeutic antibody and the full hyperthermia dose under near-infrared irradiation. Thus, SGNS with well-controlled surface morphology of gold shells may be applicable for near-infrared-induced hyperthermia therapy with tunable optical properties.