Enhancement of antitumor effect of radiotherapy via combination with Au@SiO2 nanoparticles targeted to tumor-associated macrophages

•Au@SiO2 (GNPs) were conjugated with CD163 antibody to target M2 TAM (CD163-GNPs).•M2 TAM-targeting capacity of CD163-GNPs was demonstrated.•Radiotherapy combined with CD163-GNPs showed more effective tumor growth delay than radiation alone.•Combination radiotherapy decreased the number of M2 TAMs, increasing M1 TAMs.