Real-time fluorescence tracking of gene delivery via multifunctional nanocomposites

Fluorescence imaging of transduced cells and tissues is valuable in the development of gene vectors and the evaluation of gene therapy efficacy. We report here the simple and rational design of multifunctional nanocomposites (NCs) for simultaneous gene delivery and fluorescence tracking based on ZnS:Mn(2+) quantum dots (QDs) and positively charged polymer coating. The positively charged imidazole in the as-synthesized amphiphilic copolymer can be used for gene loading via electrostatic interaction. While the introduced poly(ethylene glycol) (PEG) can be used to reduce the binding of plasma proteins to nanovectors and minimize clearance by the reticuloendothelial system after intravenous administration. Most importantly, these multifunctional nanovectors showed much lower cellular toxicity than the commercial polyethylenimine (PEI) transfection vectors. On the basis of the red fluorescence of QDs, we can real-time track the gene delivery in cells, and the transfection efficacy of pDNA encoding enhanced green fluorescence protein (pEGFP) was monitored via the green fluorescence of the GFP expressed by the pDNA delivered into the nuclei. Fluorescence imaging analysis confirmed that the QDs-based nanovectors delivered pDNA into HepG2 cells efficiently. These new insights and capabilities pave a new way toward nanocomposite engineering for fluorescence imaging tracking of gene therapy.