Gene therapy is an attractive approach to supplement a deficient gene function. Although there has been some success
with specific gene delivery using various methods including viral vectors and liposomes, most of these methods have a
limited efficiency or also carry a risk for oncogenesis.
Fluorescent nanoparticles, such as nanocrystal quantum dots (QDs), have potential to be applied to molecular biology
and bioimaging, since some nanocrystals emit higher and longer lasting fluorescence than conventional organic probes
do. We herein report that quantum dots (QDs) conjugated with nuclear localizing signal peptides (NLSP) successfully
introduced the gene-fragments with promoter elements, which promoted the expression of the enhanced green
fluorescent protein (eGFP) gene in mammalian cells. The expression of eGFP protein was observed when the QD/geneconstruct
was added to the culture media. The gene-expression efficiency varied depending on multiple factors around
QDs, such as 1) the reading direction of gene fragments, 2) the quantity of gene fragments attached on the surface of
QD-constructs, 3) the surface electronic charges varied according to the structure of QD/gene-constructs, and 4) the
particle size of QD/gene complex varied according to the structure and amounts of gene fragments. Using this QD/geneconstruct
system, eGFP protein could be detected 28 days after the gene-introduction whereas the fluorescence of QDs
was disappeared. This system therefore provides another method for the intracellular delivery of gene-fragments without
using either viral vectors or specific liposomes.
These results suggest that inappropriate treatment and disposal of QDs may still have risks to the environmental
pollution including human health under certain conditions. Here we propose the further research for the immune and
physiological responses in not only immune cells but also other cells, in order to clear the effect of all other nanoscale
products as well as nanocrystal QDs.