A research team engineered surface-modified nanodiamond particles that successfully and efficiently delivered DNA into mammalian cells. The delivery efficiency was 70 times greater than that of a conventional standard for gene delivery. The new hybrid material could impact many facets of nanomedicine.
The title of the ACS Nano paper is "Polymer-Functionalized Nanodiamond Platforms as Vehicles for Gene Delivery."
"A low molecular weight polymer called polyethyleneimine-800 (PEI800) currently is a commercial approach for DNA delivery," said Xue-Qing Zhang, a postdoctoral researcher in Ho's group and the paper's first author. "It has good biocompatibility but unfortunately is not very efficient at delivery. Forms of high molecular weight PEI have desirable high DNA delivery efficiencies, but they are very toxic to cells."
Multiple barriers confront conventional approaches, making it difficult to integrate both high-efficiency delivery and biocompatibility into one gene delivery system. But the Northwestern researchers were able to do just that by functionalizing the nanodiamond surface with PEI800.
The combination of PEI800 and nanodiamonds produced a 70 times enhancement in delivery efficiency over PEI800 alone, and the biocompatibility of PEI800 was preserved. The process is highly scalable, which holds promise for translational capability.
The researchers used a human cervical cancer cell line called HeLa to test the efficiency of gene delivery using the functionalized nanodiamonds. Glowing green cells confirmed the delivery and insertion into the cells of a "Green Fluorecent Protein (GFP)"-encoding DNA sequence. This served as a demonstrative model of how specific disease-fighting DNA strands could be delivered to cells. As a platform, the nanodiamond system can carry a broad array of DNA strands.
Regarding toxicity measurements, cellular viability assays showed that low doses of the toxic high-molecular PEI resulted in significant cell death, while doses of nanodiamond-PEI800 that were three times higher than that of the high-molecular weight PEI revealed a highly biocompatible complex.
Ho and his research team originally demonstrated the application of nanodiamonds for chemotherapeutic delivery and subsequently discovered that the nanodiamonds also are extremely effective at delivering therapeutic proteins. Their work further has shown that nanodiamonds can sustain delivery while enhancing their specificity as well.
Gene therapy holds great promise for treating diseases ranging from inherited disorders to acquired conditions and cancers. Nonetheless, because a method of gene delivery that is both effective and safe has remained elusive, these successes were limited. Functional nanodiamonds (NDs) are rapidly emerging as promising carriers for next-generation therapeutics with demonstrated potential. Here we introduce NDs as vectors for in vitro gene delivery via surface-immobilization with 800 Da polyethyleneimine (PEI800) and covalent conjugation with amine groups. We designed PEI800-modified NDs exhibiting the high transfection efficiency of high molecular weight PEI (PEI25K), but without the high cytotoxicity inherent to PEI25K. Additionally, we demonstrated that the enhanced delivery properties were exclusively mediated by the hybrid ND−PEI800 material and not exhibited by any of the materials alone. This platform approach represents an efficient avenue toward gene delivery via DNA-functionalized NDs, and serves as a rapid, scalable, and broadly applicable gene therapy strategy.
One page of supporting info for the ACS Nano paper.