Researchers say they have developed a technique that uses microscopic splinter-like structures called “nanospears” for the targeted delivery of biomolecules, such as genes to patient cells. These magnetically guided nanostructures could enable gene therapies that are safer, faster, and more cost-effective, according to the scientists.
The study (“Precision-Guided Nanospears for Targeted and High-Throughput Intracellular Gene Delivery”) appears in ACS Nano.
“An efficient nonviral platform for high-throughput and subcellular precision targeted intracellular delivery of nucleic acids in cell culture based on magnetic nanospears is reported. These magnetic nanospears are made of Au/Ni/Si (∼5 μm in length with tip diameters <50 nm) and fabricated by nanosphere lithography and metal deposition. A magnet is used to direct the mechanical motion of a single nanospear, enabling precise control of position and three-dimensional rotation. These nanospears were further functionalized with enhanced green fluorescent protein (eGFP)-expression plasmids via a layer-by-layer approach before release from the underlying silicon substrate,” write the investigators.
“Plasmid functionalized nanospears are guided magnetically to approach target adherent U87 glioblastoma cells, penetrating the cell membrane to enable intracellular delivery of the plasmid cargo. After 24 h, the target cell expresses green fluorescence indicating successful transfection. This nanospear-mediated transfection is readily scalable for the simultaneous manipulation of multiple cells using a rotating magnet. Cell viability >90% and transfection rates >80% were achieved, which exceed conventional nonviral intracellular methods. This approach is compatible with good manufacturing practices, circumventing barriers to the translation and clinical deployment of emerging cellular therapies.”
Current gene therapy approaches rely on modified viruses, external electrical fields, or chemicals to penetrate cell membranes and deliver genes to patient cells. Each of these methods has its own shortcomings; they can be costly, inefficient, or cause undesirable stress and toxicity to cells, notes senior author Paul Weiss, Ph.D., University of California Presidential Chair and distinguished professor of chemistry and biochemistry, and materials science and engineering, and member of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA.
To overcome these barriers, Dr. Weiss and Steven Jonas, M.D., Ph.D., a clinical fellow in the UCLA Broad Stem Cell Research Center Training Program, led a research team that designed nanospears composed of silicon, nickel, and gold. These nanospears are biodegradable, can be mass produced inexpensively and efficiently, and, because of their infinitesimal size—their tips are about 5000 times smaller than the diameter of a strand of human hair—they can deliver genetic information with minimal impact on cell viability and metabolism, points out Dr. Jonas, who compared the new biomolecule delivery method to real-world delivery methods appearing on the horizon.
“Just as we hear about Amazon wanting to deliver packages straight to your house with drones, we're working on a nanoscale equivalent of that to deliver important health care packages straight to your cells,” explained Dr. Jonas, who is training in the division of pediatric hematology/oncology at UCLA Mattel Children's Hospital. In the near future, Dr. Jonas hopes to apply nanotechnologies to deploy cell and gene therapies quickly and widely to the pediatric cancer patients he treats.
Drs. Weiss and Jonas are not the first to conceive of using guided nanostructures or robotic “nanomotors” to enhance gene therapies; however, existing methods have limited precision and require potentially toxic chemicals to propel the structures to their targets.
By coating their nanospears with nickel, Drs. Weiss and Jonas eliminated the need for chemical propellants. A magnet can be held near a lab dish containing cells to manipulate the direction, position, and rotation of one or many nanospears. In the future, the team envisions that a magnetic field could be applied outside of the human body to guide nanospears remotely within the body to treat genetic diseases.
Drs. Weiss and Jonas tested their nanospears as vehicles for a gene that causes cells to produce a GFP. About 80% of targeted cells exhibited a bright green glow, and 90% of those cells survived. Both numbers are a marked improvement on existing delivery strategies.
Much like gene therapy, many forms of immunotherapy rely on expensive or time-consuming processing methods.
“The biggest barrier right now to getting either a gene therapy or an immunotherapy to patients is the processing time,” Dr. Jonas said. “New methods to generate these therapies more quickly, effectively, and safely are going to accelerate innovation in this research area and bring these therapies to patients sooner, and that's the goal we all have.”