Herein, we optimize a method for the synthesis and bioconjugation of water-soluble, fluorescent CdSe/ZnS quantum dots (QDs) for targeted cellular delivery of DNA. First, core CdSe QDs were synthesized in high temperature organic solvents and passivated with a ZnS shell to increase quantum yield. Then, the fluorescent QD nanoparticles were made water-soluble by enveloping them with an amphiphilic polymer (Poly(maleic anhydride-alt-1-tetradecene), 3-(dimethylamino)-1-propylamine). These aqueous nanoparticles were further functionalized with N,N-dimethylpropylenediamine to impart a positive charge, allowing the QD surface to participate in electrostatic binding to negatively-charged DNA. The stoichiometry of N,N-dimethylpropylenediamine was varied in multiple reactions to determine the relative degree of functionalization needed to effectively complex DNA. While some positive charge is needed to bind DNA, excess positive charge is potentially toxic to live cells. Gel electrophoresis confirmed the ability of our QDs to bind and hold DNA. The QDs were then further modified by conjugation with Wheat Germ Agglutinin (WGA) (a carbohydrate-binding protein) to direct the nanoparticle trafficking within the cell. Gel electrophoresis was used to characterize the final multifunctionalized QDs. We observed the effect of this conjugation to the QD using fluorescence[KF1] microscopy and immunocytochemistry to visualize the trafficking within N2a (mouse neuroblastoma) cells.

Nonviral gene therapy applications of multifunctional fluorescent quantum dots

249th National Meeting (2015)

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