GFP expression by intracellular gene delivery of GFP-coding fragments using nanocrystalquantum dots

Abstract

Gene therapy is an attractive approach to supplement a deficient gene function. Althoughthere has been some success with specific gene delivery using various methods includingviral vectors and liposomes, most of these methods have a limited efficiency oralso carry a risk for oncogenesis. We herein report that quantum dots (QDs)conjugated with nuclear localizing signal peptides (NLSP) successfully introducedgene-fragments with promoter elements, which promoted the expression of the enhancedgreen fluorescent protein (eGFP) gene in mammalian cells. The expression ofeGFP protein was observed when the QD/gene-construct was added to the culturemedia. The gene-expression efficiency varied depending on multiple factors aroundQDs, such as (1) the reading direction of the gene-fragments, (2) the quantity ofgene-fragments attached on the surface of the QD-constructs, (3) the surface electroniccharges varied according to the structure of the QD/gene-constructs, and (4) theparticle size of QD/gene complex varied according to the structure and amounts ofgene-fragments. Using this QD/gene-construct system, eGFP protein could bedetected 28 days after the gene-introduction whereas the fluorescence of QDs haddisappeared. This system therefore provides another method for the intracellulardelivery of gene-fragments without using either viral vectors or specific liposomes.