Preparation, Characterization And Modification Of Dendrimer Capped Gold Nanoparticles

Gold nanoparticles have good stability, excellent surface effect, unique optical speciality and special biological affinity. Gold nanoparticles can counjucte with biomolecules and can be used as biological probes. The colour of gold nanoparticles changes from red to blue with the increase of the diameter of nanoparticles. The change can be used as a signal readout to detect biomolecules because of its consistency and visibility. These characteristics of gold nanoparticles help simplify and speed up detection processes, therefore, they have been widely used for DNA and protein detection in biological assays.In this study, PPIHA (DAB-AM-16, Polypropylenimine Hexadecaamine Dendrimer, Generation 3.0) dendrimer was used as both reducing agent and propecting agent to prepare gold nanoparticles by heating an aqueous solution containing PPIHA and HAuCl₄. In the process of synthesis, gold nanoparticles were modified with multiamino groups, which made them capable of conjugating with biomolecules directly. This way, the aggregation of gold nanoparticles was avoided. Conditions on the preparation of gold nanoparticles were optimized, and the best condition to prepare monodispersed, uniform and steady nanoparticles was identified. In addition, nano-gold preparation using both NaBH₄ and PPIHA were conducted to study the role of PPIHA by comparing of the two methods. UV-vis spectrophotometer, transmission electron microscopy and granularity analyzer were used to characterize the gold nanoparticles. The results obtained from the three detection methods showed the same trends.Gold nanoparticles prepared by PPIHA were also used as probes to detect DNA and to do simple quantitative analysis of BSA. The gold nanoparticles labeled with amino groups were connected with 3'or 5'labeling phosphate oligonucleotides. The colour changed from red to purple after gold nanoparticles labeled target oligonucleotides were mixed with complementary oligonucleotides labeled with gold nanoparticles. The absorbance of Au-BSA...