In vitro/in vivo “peeling” of multilayered aminocarboxylate gold nanoparticles evidenced by a kinetically stable 99mTc-label

Abstract

A thiolated bombesin peptide was conjugated to Au-DTDTPA nanoconstructs to obtain BBN-Au-DTDTPA targeted to the gastrin releasing peptide receptor (GRPr). Different analytical techniques showed that this conjugate shares similar physico-chemical properties with Au-DTDTPA; HPLC and XPS analyses corroborated the attachment of the bioactive peptide to the AuNPs surface. Competitive binding assays in PC3 cancer cells showed that these BBN-containing AuNPs have high affinity for GRPr. BBN-Au-DTDTPA was successfully radiolabeled with ^99mTc and showed high in vitro stability towards different biological media and substrates, except for glutathione (GSH). In vitro and in vivo studies, based on gamma-counting (^99mTc content) and neutron activation analysis (Au content), indicated the release of the DTDTPA coating from the AuNPs. Probably, the “peeling” of the layered-aminocarboxylate coating is GSH-mediated and involves the cleavage of the DTDTPA disulfide bonds and/or Au–S bonds. These results render BBN-Au-DTDTPA an interesting platform deserving further evaluation in target-specific GSH-mediated drug delivery.