Functional Dendrimer-Based Gold-Silver Alloy Nanowires By Hydrothermal Routine For CT Imaging Of Cancer Cells In Vitro

As one of the most commonly used techniques for disease diagnosis, the electronic computer X-ray tomography technique (CT) has been widely used in many biomedical applications such as bone imaging, anatomy imaging and tumor imaging. The development of CT imaging contrast agents with multi-function, high sensitivity and specificity to improve the accuracy of early diagnosis of the tumors has become the research trend of nanomedicine and molecular imaging. In recent years, amine-terminated poly(amidoamine) dendrimers (PAMAM) used as templates to encapsulate or stabilize inorganic nanomaterials for CT contrast agents have been attracted a wide attention due to the nanomaterial’s unique physical and chemical properties, good biocompatibility, long circulation time and high atomic number. In this study, the fifth generation PAMAM (G5.NH2) were used as stabilizers to synthesize gold-silver alloy nanowires via hydrothermal routine, followed by modification with targeting ligand folic acid (FA) through amino groups on the surface and subseqent acetylation of the rest amino moieties (acetylated Au-Ag NWs-FA). Finally the formed novel functional nanowires were used as CT contrast agents and compared with FA-modified acetylated dendrimer-stablized Au-Ag alloy nanoparticles (acetylated Au-Ag DSNPs-FA) in terms of the cellular uptake when treated with cancer cells in vitro.First of all, using G5.NH2as templates and with the mole ratio of G5.NH2/HAuCl4/AgNO3of1/15/5, colloidally stable Au-Ag NWs with mean diameter ranging from1-2nm were synthesized via moderate water bath reduction method. Then, the NWs were modified with targeting ligands FA through the amino groups on the surface, and lastly we obtained the multifunctional targeted CT contrast agents after complete acetylation with acetic anhydride. The prepared multifunctional targeted CT contrast agents were characterized with1H NMR, UV-Vis spectrometry, TEM, ζ -potential measurements and X-ray attenuation intensity measurements in vitro, respectively. In addition, the cytotoxicity of the NWs were evaluated by MTT assay and phase contrast microscope. The targeting and CT imaging capability in vitro of the formed NWs were assessed via human oral cancer cell line (KB cells). Finally, the cellular uptake of the formed NWs by KB cells was compared with that of acetylated Au-Ag DSNPs-FA synthesized according to the protocol in our previous study.Our results showed that acetylated Au-Ag NWs-FA were successfully synthesized and are colloidally stable under different temperature (4,20,37,57℃) or pH (5,6,7,8) conditions.The MTT results demonstrated that the functional acetylated Au-Ag NWs-FA have a good biocompatibility even when material concentration is up to3000nM. X-ray attenuation intensity measurement and CT scanning showed that the fomed NWs display a good targeting capability to KB cells highly overexpressing FA receptor and a higher X-ray attenuation intensity than clinically used iodine-based small molecule contrast agent Omnipaque. Finally, the comparison of cellular uptake of FA-modified acetylated NWs and NPs by KB cells indicated that there was no appreciable difference in cellular uptake between the two types of nanomaterials with similar composition but totally different morphologies.