Modifying red blood cells for safe and effective drug delivery

Abundant and persistent, red blood cells have a lifetime of about four months in the human body and travel to every organ and tissue. They could soon be leveraged to transport more than oxygen and carbon dioxide.

A team led by researchers at Carnegie Mellon University is receiving $5.4 million from the Defense Advanced Research Projects Agency (DARPA) to develop technologies for loading red blood cells with drug molecules. DARPA's Red Blood Cell Factory (RBC-Factory) program aims to create a medical device-based platform to insert biologically active components, like proteins and peptides, into red blood cells to provide enduring protection for service members in challenging environments.

The 21-month project, titled Visco-Elastic Large Volume Erythrocyte Transfection (VELVET), will study the feasibility of a new method for loading diverse components into red blood cells. Developed by Derin Sevenler, the method could enable delivery of medication at safe, effective, and consistent concentrations for extended periods of time. For example, drug molecules designed to remain inactive while inside the red blood cells could become active upon release when those cells are naturally recycled by the body.

"The vision is a single outpatient procedure with a therapeutic effect that lasts for months," says Sevenler, assistant professor of chemical engineering.

The Sevenler Lab is developing a device to load drug molecules into red blood cells taken from a standard blood draw, with the goal of eventually infusing the drug-loaded cells back into the patient. They use manufacturing techniques originally developed for computer chips to make microfluidic devices that can precisely manipulate biological samples like cells.

Inside the microfluidic device, Sevenler's design takes advantage of the nonlinear mechanical properties of viscoelastic fluids. Cells are exposed to an extremely brief but intense pulse of stretching forces, which creates leaky pores in the cell membrane. These pores stay open for a few seconds, long enough to efficiently deliver molecules into the cell by molecular diffusion.

Previous research has found that existing methods of making a hole in a red blood cell can shorten the lifetime of the cell. The membrane is weakened, the cell becomes more fragile, and it is cleared by the body faster.

Membrane damage can also activate the immune system. Immune cells recognize certain changes in the membrane structure, identify those red blood cells as damaged, and destroy them. "We want to understand if we can develop methods that keep these modified red blood cells in circulation for their natural lifetimes," says Sevenler.

Another limitation of existing methods is that they can only load small molecules into red blood cells, leaving out an important class of drugs based on larger biological molecules like proteins.

Sevenler's proposed method is gentler on cells, can be used with both large and small molecules, and is uniquely high-throughput. The ability to modify billions of cells per minute is critical because potential clinical applications will require loading medication into a lot of red blood cells.

"If we can increase the amount of medication we can load into the cells, that will open up more possibilities for which treatments can be delivered this way," says Sevenler.

Sevenler is leading a multidisciplinary team of experts in microfluidics, intracellular delivery, bio-nanotechnology, biomedical devices, transfusion medicine, and technology policy. Within Carnegie Mellon's College of Engineering, Daphne Chan and Jim Schneider are leading the development and formulation of different molecules to maximize how much can be loaded into red blood cells. Kathryn Whitehead and Phil Campbell are working to understand if and how the immune system recognizes a red blood cell that has been modified by this process and how to keep those cells from being destroyed. Doron Cohen will assess the ethical, legal, and societal impacts of the new technology. Joining them are Susan Shea at the University of Pittsburgh Trauma and Transfusion Medicine Research Center and Lu Li in the Robotics Institute at Carnegie Mellon.

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Provided by Carnegie Mellon University Chemical Engineering