One of the most popular methods for inserting therapeutic genes into cells to treat disease is to transport them using a virus that has been stripped of its infectious properties. But those noninfectious viruses can still sometimes touch off dangerous immune responses.
A team from Johns Hopkins Medicine is proposing an alternative method for transporting large therapies into cells—including genes and even the gene-editing system CRISPR. It’s a nano-container made of a polymer that biodegrades once it’s inside the cell, unleashing the therapy. The researchers described the invention in the journal Science Advances.
The team, led by biomedical engineer Jordan Green, Ph.D., was inspired by viruses, which have many properties that make them ideal transport vehicles. They have both negative and positive charges, for example, which allows them to get close to cells. So Green and his colleagues developed a polymer containing four molecules with both positive and negative charges. They used it to make a container that interacts with the cell membrane and is eventually engulfed by it.
The Hopkins researchers performed four experiments to prove the nanocontainers would travel into cells and deliver complex therapies once inside. First, they packaged a small protein into the polymer material and mixed it with mouse kidney cells in a lab dish. Using fluorescent tags, they confirmed that the protein made it into the cells. Then they repeated the experiment with a much larger medicine—human immunoglobulin—and observed that 90% of the kidney cells received the treatment.
From there, they made the payload even bulkier, packaging the nanocontainers with the gene-editing system CRISPR. With the help of fluorescent signals, they were able to confirm that CRISPR went to work once inside the cells, disabling a gene 77% of the time.
"That's pretty effective considering, with other gene-editing systems, you might get the correct gene-cutting result less than 10 percent of the time," said graduate student Yuan Rui in a statement.
Finally, the Hopkins researchers injected CRISPR components into mouse models of brain cancer using the polymer nanocontainers. Again they saw evidence that successful gene editing had occurred.
Developing improved methods for gene therapy is a priority in the field. In October, for example, scientists at Scripps Research described a way to use a small molecule called caraphenol A to lower levels of interferon-induced transmembrane (IFITM) proteins, which could, in turn, allow viral vectors to pass more easily into cells. And earlier this year, an Italian team described a method for including the protein CD47 in lentiviral vectors to improve the transferring of therapeutic genes into liver cells.
The next step for Hopkins researchers Rui and Green is to improve the stability of the nanocontainers so they can be injected into the bloodstream. They hope to be able to target them to cells that have certain genetic markers, they reported.