Acetylation-Mediated Synthesis And Characterization Of Dendrimer-Stabilized Silver Nanoparticles

Silver nanoparticles (AgNPs) continue to receive intense scientific and technological interest in the applications of optics, electronics, catalysis, sensing, and so forth. For synthesizing silver nanoparticles, three methods are often employed including physical, chemical, biologic methods. Synthesizing AgNPs with tunable sizes and desired stability is of great difficulty for current research. With the development of metal nanoparticles carrier, PAMAM dendrimer was found to be a promising carrier. Employing PAMAM dendrimer in the preparation process can solve the problems stated above, forming metal nanoparticles with certain size and desired stability. In our previous work, we employed PAMAM dendrimer as template and stabilizer, getting dendrimer-stabilized Ag nanoparticles (Ag DSNPs). These products possess uniform size and desired stability.In this present study, we systematically investigated the effect of the molar ratio Ag(I)/G5.NH2 on the size of Ag DSNPs using a method of acetylation. We investigated the stability of Ag DSNPs in different conditions, as well as theirs biocompatibility and X-ray attenuation property. In addition, we preliminarily investigated the properties of Au-Ag bimetal NPs in the last chapter of this paper. The main content of this paper include several parts:(1) Synthesis, characterization of dendrimer-stabilized silver nanoparticles (Ag DSNPs). The size-controllability of silver nanoparticles is researched, as well as the optics, electricity, morphology property of all products. (2) Investigating the stability of Ag DSNPs at different pH, temperature and solvent conditions. Through measure and test, the stability of Ag DSNPs can be evaluated. (3) Investigating the X-ray attenuation property of Ag DSNPs in vitro. Experiments were done between Ag DSNPs and between Ag DSNPs and a traditional contrast agent Omnipaque. (4) Investigating the biocompatibility of Ag DSNPs, using MTT assay. (5) Synthesis of Au-Ag bimetal based on G5.NH2 dendrimer. The effect of Au:Ag:dendrimer molar ratio on the optical property of bimetal is researched. (6) Investigating the stability of Au-Ag bimetal at different pH and temperature conditions. (7) Investigating the X-ray attenuation property of Au-Ag bimetal in vitro.The results of this research work are as follows:(1) By regulating the Ag(Ⅰ)/G5.NH2 molar ratio, a series of Ag DSNPs are synthesized, named{(Ag0)25-G5.NHAc},{(Ag0)50-G5.NHAc}, {(Ag0)75-G5.NHAc},{(Ag0)100-G5.NHAc} DSNPs. In UV-vis spectrum, the SPR peak at 412 nm indicates the existence of AgNPs. From TEM test, we can see that the size of formed AgNPs are in the range of 8.8～23.2 nm with uniform size distribution. (2) All formed Ag DSNPs have satisfactory stability at different pH (5～8), temperature (25～50℃), solvent (distilled water, PBS buffer, fetal calf serum) conditions. (3) In intro X-ray attenuation test show that {(Ag0)75-G5.NHAc} DSNPs display better X-ray attenuation coefficient than others and show a similar property to Omnipaque. (4) MTT assay show{(Ag0)75-G5.NHAc} DSNPs display well biocompatibility when Ag concentration below 2000 nM. (5) By regulating the Au:Ag:dendrimer molar ratio, a series of bimetal are synthesized, including before and after acetylation materials. The SPR peak of bimetal appeared is in the range between 413 nm, due to pure silver particles, and 530 rim, due to pure gold ones. (6) All formed Au-Ag bimetals have satisfactory stability at different pH (5-8) and temperature (4～50℃) conditions. (7) In intro X-ray attenuation test shows that the X-ray attenuation coefficient of bimetal increased with the increase of Au content in bimetal, gradually displaying better X-ray attenuation coefficient than Omnipaque, a traditional contrast agent.We can get conclusions as follows:dendrimer/silver nanocomposites are formed with satisfactory stability and controllable size. This is expected to optimize and extend the application of AgNPs and provide a new way to synthesis metal nanoparticles. The formed products display well biocompatibility and similar X-ray attenuation coefficient to Omnipaque, expecting to develop a new kind of CT contrast agent for medical molecular imaging. In addition, we synthesized a series of bimetal, investigated their stability and in vitro X-ray attenuation coefficient, laying the first stone for developing a new CT contrast agent.