Combined Photothermal and Chemotherapy to Induce Cancer Cell Damage in Spheroids Using Gold Nanostars and Gold Nanorods

ABSTRACT Gold nanostars (GNS) show great potential for cancer therapy due to their photothermal effect under near‐infrared excitation. Here we propose to combine photothermia with chemotherapy to make the treatment more efficient. GNS were prepared by a seeded‐growth method involving silver nitrate in a 1‐min process. The optimal conditions were 15 nm seeds, 3 m m of silver nitrate and a seeds to gold chloride ratio of 0.004 to obtain plasmonic resonance at 807 nm. These optimized GNS showed an increase of 4°C upon 808 nm excitation. Photothermal properties were similar to those of commercial gold nanorods (GNR) with a plasmon band centered at 813 nm. Then GNS and GNR were modified with PEG‐SH molecules in order to incubate them with HT29 cancer cell spheroids prepared in hydrogel microwells. Spheroids were submitted to various treatments, in addition to incubation with GNS and GNR. They were also incubated with gemcitabine, a chemo‐therapeutic agent, and irradiated at 808 nm, with the objective to combine chemotherapy with photothermal therapy. The dead/live cell evaluation after treatment was performed by fluorescence microscopy. The optimal combination of GNS, gemcitabine, and laser irradiation was found to induce the highest percentage of dead cells and a decrease of spheroids size.