Photothermal Therapy Employing Gold Nanoparticle-Loaded Macrophages as Delivery Vehicles: Comparing the Efficiency of Nanoshells Versus Nanorods

Macrophages (Ma) loaded with gold-based nanoparticles, which convert near infrared light to heat, have been studied as targeted transport vectors for photothermal therapy (PTT) of tumors. The purpose of the experiments reported here was to compare the efficacy of gold-silica nanoshells (AuNS) and gold nanorods (AuNR) in macrophage-mediated PTT. Photothermal therapy efficacy was evaluated in hybrid glioma spheroids consisting of human glioma cells and either AuNS-or AuNR-loaded Ma, designated Ma(NS) and Ma(NR), respectivly. Spheroids were irradiated for 10 minutes with light from an 810-nm diode laser at irradiances ranging from 0 to 28 W/cm(2). Photothermal therapy efficacy was determined from spheroid growth over a 14-day period. The uptake by Ma of pegylated AuNR (3.9 +/- 0.9 %) was twice that of pegylated AuNS (7.9 +/- 0.7%). Hybrid spheroids consisting of a 5:1 ratio of glioma cells to loaded Ma exhibited significant growth inhibition with Ma(NS) when subjected to irradiances of 7 W/cm(2) or greater. In contrast, no significant growth inhibition was observed for the Ma(NR) hybrid spheroids at this 5:1 ratio, even at the highest irradiance investigated (28 W/cm(2)). Although Au-NR were taken up by Ma in larger numbers than AuNS, Ma(NS) were shown to have greater PTT efficacy compared to Ma(NR) for equivalent numbers of loaded Ma.