(click to enlarge)
The top illustration shows blood cells' normal reaction to a carbon nanotube. Adding the heparin coating (bottom) may help with biocompatibility. Artwork courtesy of RPI (Troy, NY).
The material could have significant uses in the device field, such as for a kidney-dialysis filter. According to research team leader Robert J. Linhardt, PhD, the material would offer a way of updating dialysis machines. “Dialyzers are routinely used for patients with kidney failure,” he says. “Our approach would make materials used to fabricate devices more blood compatible and less likely to clot and clog.”
Linhardt is a professor of biocatalysis and metabolic engineering at RPI. Heparin, he explains, is already used during therapies to maintain blood flow, such as blood oxygenation, deep vein thrombosis, and kidney dialysis. But the drug could cause severe side effects when administered intravenously or subcutaneously. Most researchers agree that binding the heparin to a specific device, rather than traditional delivery, cuts down on possible side effects, which include uncontrolled bleeding.
Binding heparin to nanoscale materials, however, opens up even further opportunities for biocompatibility. “Our long-term goal is to make materials that can be used to fabricate devices that are biocompatible,” Linhardt says. “These could be macrodevices, such as kidney dialyzers, used externally in extracorporeal circuits; as nanodevices used internally in drug-delivery systems; or as implantable nanomachines.”
To create the coating, Linhardt and his team used liquid salt solvents called room-temperature ionic liquids. “This solvent is one of a small number of solvents capable of dissolving cellulose and heparin,” he notes. According to the team, the solvent does not evaporate and can be recovered and reused in processes.
The researchers prepared several materials with heparin composites or coatings. They then demonstrated that the various materials, including carbon nanotubes, nanofibers, and membranes with nanosized pores, exhibited high compatibility with blood. The study was published in the online version of the Journal of Biomedical Materials Research.
Linhardt is optimistic about the next stages of development. The team is planning to make hollow fibers using a cellulose-heparin composite. The fibers can then be incorporated into devices. “This next generation of blood-compatible dialyzers will have to be evaluated in clinical studies and approved by FDA,” he says.
In addition, Linhardt says, the RPI group is looking at other opportunities to further the technology. “We are exploring the immobilization of enzymes on these biocompatible nanotubes for spinal cord regeneration. We are also looking at these materials to make artificial blood vessels.”
Linhardt says his team is “actively seeking corporate partners to take this work to the next level.” The work with heparin-coated nanodevices is a spin-off from research grants from the National Institutes of Health.