Researchers J.J. Green, S.Y. Tzeng, H. Guerrero-Cázares, and their colleagues at the Johns Hopkins University School of Medicine have developed a technique that delivers gene therapy into human brain cancer cells using polymer-DNA nanoparticles that can be freeze-dried and stored for up to three months prior to use.
The shelf-stable nanoparticles may obviate the need for virus-mediated gene therapy, which is associated with a number of safety concerns. The report appears in the August issue of Bio materials (DOI:10.1016/j.biomaterials. 2011.04.016; p. 5402).
“Most nonviral gene therapy methods have very low efficacy,” said Green, an assistant professor of biomedical engineering at Johns Hopkins. “Nanoparticle-based gene therapy has the potential to be both safer and more effective than conventional chemical therapies for the treatment of cancer.”
To develop the nanoparticles, Green’s team prepared a library of cationic poly(b-amino esters) from commercially-available small molecules. They then mixed DNA that encodes a glowing protein with each different polymer to allow the DNA to bind to the polymers and form polymer-DNA nanoparticles. Each different sample was added to human brain tumor and glioblastoma cells. After 48 hours, the team examined and counted how many cells glowed. These cells had taken up the nanoparticles and synthesized the fluorescent protein encoded by the introduced DNA.
The team rated success by counting how many cells survived, and what percentage of those glowed.
Of the many combinations tested, the researchers found that one particular formulation of polymer nanoparticles were particularly successful in entering both glioblastoma and brain tumor stem cells. These nanoparticles were then freeze-dried and stored at different temperatures (freezer, refrigerator, and room temperature) for between one and three months. Their ability to be taken up by the cells was then re-tested. According to Green, after six months in storage, the effectiveness dropped by about half, but there was virtually no change in effectiveness after three months of storage at room temperature.
Furthermore, the team found that certain nanoparticles had a particular affinity for brain tumor cells over healthy brain cells.
Brain cancer cells produce a green fluorescent protein. DNA encoded to produce the protein was delivered to the cancer cells by freeze-dried polymer-DNA nanoparticles. Credit: Stephany Tzeng.
“I could imagine particles based on this technology being used in conjunction with, and even instead of brain surgery,” said A. Quiñones-Hinojos, an associate professor of neurosurgery and oncology at Johns Hopkins.
