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Synthesis and Ft-Irras Characterization of Ir-Active Bionanomaterias from Fourth Generation Polyamidoamine Dendrimer

Zheng Liu, Catalyst Technology and Emission Chemistry, Cummins Inc, 1900 McKinley Ave., CTC-MC 50183, Columbus, IN 47203 and Ping Yang, Department of Chemistry, East China Normal University, Shanghai, 200062, China.

Fourth generation amine-terminated polyamidoamine (G4 PAMAM) dendrimer with 64 surface amine groups available is used as nano-core for conjugation with biotin and a suitable organometallic carbonyl reagent (IR label). IR active biotinylated dendrimer (Bio-dendrimer) has been synthesized via a two-step process involving the reaction of the dendrimer with a cobalt-carbonyl complex followed by reaction with NHS-biotin. The as-prepared Bio-dendrimer coupled with the organometallic complex is IR-active, exhibiting three intense nC≡O bands in the mid-infrared spectral range (1800-2150 cm-1), arising from the (Co)2(CO)6 complex. An initial attempt to control this ratio has made by adjusting the reaction order of G4 PAMAM dendrimer with biotin and the IR-active complex, as well as the reaction temperature, solvent, and the concentration of reagents. The concentration of biotin and (Co)2(CO)6 unit immobilized onto G4 PAMAM dendrimer was determined through FT-IRRAS (Fourier Transform Infrared Reflection Absorption Spectroscopy) measurements. Finally, the individual Bio-dendrimer thus obtained was organized into different types of bio-aggregates through the specific interaction/ recognition of the biotin moiety with the four biotin-binding sites of the avidin-DNA conjugate. As expected, the resulting bio-aggregates from bio-dendrimer display much more intense IR-signals than the individual Bio-dendrimer in the characteristic region of the metal carbonyl unit. The size and structure of bio-aggregate can be controlled by regulating the content of the biotin moiety. Our ultimate goal is to synthesize well-defined bio-aggregate with IR-activity, and take advantage of its IR feature to recognize and quantify target biomolecules.