A convenient method of preparing gene vector for real time monitoring transfection process based on the quantum dots

Nanoparticle carrier has been developed by combining water-soluble quantum dots and plasmid DNA expressed enhanced green fluorescent protein (EGFP) in a convenient and direct way. First the QDs with different surface charges were obtained by coating with amino and carboxyl terminals at different ratios. Then plasmid DNA was conjugated to QDs via electrostatic interaction. The resultant QDs–DNA complexes showed enhanced resistance to DNase I digestion. The following transfection experiments demonstrated that the transfection efficiency was dependent on the surface charges on QDs. The real time imaging of the transfection process showed that the nanoparticles experienced binding, penetrating the cell membrane and entering cytoplasm in the first 6 h of transfection. The green fluorescence of EGFP began to appear after 18 h transfection and plasmid DNA was fully expressed in the following 6 h. This new QDs–DNA platform showed great potential as new gene delivery carrier.

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► An easy and direct way to prepare QDs–DNA complexes was developed.
► Surface charge of QDs was tuned with different ratio of amino and glycolate.
► Transfection efficiency was dependent on the surface zeta potentials of QDs.
► Cellular toxicity of this gene vectors is much lower than commercial liposome.
► Whole intracellular behavior of QDs–DNA complexes can be monitored in real time.