A nanotechnology-based delivery system: Nanobots. Novel vehicles for molecular medicine

We previously demonstrated that adenovirus-mediated p53 gene transfer following balloon angioplasty, decreased neointimal hyperplasia. However, safety concerns arise because viral promoters can cause unrestricted transgene expression. The paucity of safe and efficient vehicles for gene transfer thus limits the potential for clinical utilization of gene therapy. Our objective was to design and clone a virus-free p53 construct, targeted to express specifically in vascular smooth muscle cells (SMCs), via a nanoparticle-based delivery system for therapeutic modulation in vascular wall.

Biodegradable poly(lactide-co-glycolide) (PLGA), an FDA approved polymer, was used to formulate the nanoparticles. Cloned constructs consisting of SMC promoter, SM22, and p53 cDNA sequences along with enhanced green fluorescent protein (EGFP) gene, were loaded into PLGA nanoparticles. The affect of these nanobots on cell growth was examined.

The gene sequences carried by the nanobot are expressed in target cells. The p53/EGFP construct under the constitutive promoter was found to express in 293T human embryonic kidney cells, whereas the p53/EGFP with SMC promoter expressed only in human aortic SMCs. SMCs internalize these nanobots without compromising cell viability or growth kinetics.

A novel genetic sequence that targets a specific cell population has been successfully designed, cloned and encapsulated in a nanoparticle. This experiment is a significant step towards the development of a nanoparticle-based delivery system for therapeutic delivery of targeted gene-therapy towards attenuation of restenosis. Further work is necessary to expand the repertoire of this delivery system and determine whether it could become a versatile vehicle in molecular medicine.