Aptamer Grafting onto (on) and into (in) Pegylated Gold Nanoparticles: Physicochemical Characterization and In vitro Cytotoxicity Investigation in Renal Cells

Gold Nanoparticles (AuNPs) have already a remarkable interest as viable biomedical materials. Additionally, the strategy of using biomolecules to modify their surface properties is a very attractive as it leads to the generation of new nanometric hybrid materials. In this respect, aptamers, functional small single-strand oligonucleotides (DNA or RNA), are ideal candidates for molecular targeting applications since the high affinity to their target molecules. Thus, the urge of new and effective methodologies to graft aptamers on AuNPs is rapidly increasing especially for applications in bioanalysis and biomedicine, including early diagnosis and drug delivery. Here we used two chemical methodologies to conjugate the aptamer (APT) onto pegylated gold nanoparticles (PEG-AuNPs): the carbodiimide chemistry (EDC/NHS) (methodology ON) and the chelation-bond (R-Au bond) (methodology IN). The aptamer's conjugations with the PEGAuNPs were characterized by UV-Vis absorption, Raman Spectroscopy and transmission electron microscopy (TEM). In addition, the potential nanotoxicity of the two aptamer-conjugated AuNPs was evaluated on two different renal cell lines, being the kidneys one of the most important site of bioaccumulation upon systemic circulation. Interestingly, the two aptamer-conjugated AuNPs showed different cytotoxicity when exposed to human embryonic kidney (HEK293) and mouse collecting duct cells (M-1), indicating that cell viability has to be taken into account when choosing the proper strategy for NPs production. In conclusion this study provides two effective methods to graft aptamers on NPs and important insights regarding NPs conformation and the relative cell viability.