Gold nanoclusters (AuNCs) have attracted much attention for tumor theranostics in recent years because of their ability of renal clearance and to escape the reticuloendothelial system (RES) sequestration. In this study, we presented a novel method to synthesize 68Ga-doped (labeled) AuNCs by simultaneous reduction of 68GaCl3 and HAuCl4 by glutathione. As synthesized 68Ga-doped, glutathione-coated AuNCs (68Ga-GSH@AuNCs) were ultrasmall in size (<2 nm), highly stable under physiological conditions and renally clearable, and had high efficiency for tumor targeting. To demonstrate the universality of this 68Ga labeling method and further enhance tumor targeting efficiency, arginine-glycine-aspartate (RGD)-containing peptide was introduced as co-reductant to synthesize RGD peptide and glutathione co-coated, 68Ga-labeled AuNCs (68Ga-RGD-GSH@AuNCs). Introduction of RGD peptide did not interfere the synthesis process but significantly enhanced the tumor targeting efficiency of the AuNCs. Our study demonstrated that it was feasible to label AuNCs with gallium-68 by direct reduction of the radioisotope and HAuCl4 with reductant peptides, holding a great potential for clinical translation for PET/CT detection of tumors.
Keywords: Gallium-68; Gold nanoclusters; PET/CT imaging; RGD peptide; Renal clearance; Tumor targeting.
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