Date of Award

January 2011

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Joseph M. Piepmeier

Subject Area(s)

Neurosciences, Biomedical engineering

Abstract

Glioblastoma multiforme, an aggressive malignant tumor, continues to be amongst the most fatal disorders in medicine despite many therapeutic techniques and drug discoveries. Malignant brain tumor cells' ability to invade surrounding brain parenchyma is the main reason for treatment failure and recurrence. Traditional chemotherapy methods have found difficulty accessing the brain due to the blood-brain barrier, while irradiation techniques cause damaging effects on normal regions of the brain. New forms of gene therapy have been found to eliminate tumor cells, while sparing healthy brain tissue; however, with no efficient delivery mechanism gene therapy has been unable to access a large amount of tumor cells to eliminate the tumor mass and prevent the likelihood of recurrence. Local delivery of gene therapy has introduced a new method that looks to solve this problem, by delivering therapy directly to the brain tissue. One method of local delivery is convection-enhanced delivery (CED) of poly(lactic-co-glycolic acid) (PLGA) nanoparticles, a biocompatible polymer material. Using a catheter and pump, this intracranial drug delivery method allows for drug-loaded nanoparticles to be released directly into brain tissue in a bulk flow of fluid. This method bypasses the blood-brain barrier and has a large distribution volume which has direct access to the tumor mass.

The efficacy of CED of siRNA nanoparticles on suppressing gene expression in tumor cells was studied in both in vitro experiments and in vivo rat models. Fisher 344 rats were used as the animal model and 9L gliosarcoma cells, a highly aggressive malignant tumor, labeled with enhanced green fluorescent protein (EGFP) were the tumor source. Small interfering RNA targeting the EGFP gene (siEGFP) were encapsulated into PLGA nanoparticles and used as a gene therapy. Our study shows that siEGFP nanoparticles are capable of causing in vitro and in vivo gene expression reductions of up to 50 and 60%, respectively. When 9L cells were exposed to small interfering epidermal growth factor receptor (siEGFR), which targets the EGFR gene, in vitro growth suppression was observed that reduced 9L cell growth by 89% compared to the untreated control. These gene knockdown results shown in this thesis suggest that siRNA-loaded PLGA nanoparticles provide a great potential means for treating tumors.

Comments

This is an Open Access Thesis.

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