Japanese researchers study carbon nanotubes with drug delivery applications

Researchers across the world are scrambling to invent new technologies made out of graphene, perfectly flat sheets of carbon atoms that are only one atom thick. For instance, South Korea's Samsung is developing foldable screens made out of graphene, while the European Union is devoting €1 billion ($1.1 billion) to study the potential material of the future, which is a truly 2-D material, with no dangling bonds to bind with surfaces above or below it.

Meanwhile, the U.S. National Institutes of Health is funding American companies like Graphene Frontiers, maker of a point-of-care diagnostic device that can detect heart attack biomarkers from a drop of blood within minutes, thanks to the use of the company's namesake material.

Now scientists at Japan's Kyushu University claim to have developed a technique for dispersing carbon nanotubes made of graphene, which otherwise have a tendency to cluster together or form aggregates, while preserving their desirable properties like conductivity, durability and length.

Graphene nanotubes with appropriate coatings can pass through biological barriers without triggering the immune system. "Once the CNTs are stably wrapped with biocompatible materials, they are extremely attractive for biomedicine due to their incredible ability for passing biological barriers across the cytoplasmic and nuclear membrane without generating an immunogenic response. Many researchers have focused on the potential of CNTs for drug delivery, which might be attributed to their exclusive physicochemical features," two Kyushu University researchers write in a literature review published in the journal IOPscience.

Without the use of dispersants that coat the nanotubes, they tend to clump together, reducing their viability for functions like drug delivery. Kyushu University says the key to their coating's success is that it is a noncovalent polymer wrapping, meaning that their bond with nanotubes does not involve the sharing of electrons. Covalent bonds are stronger but reduce the desired properties of graphene-based materials.

Graphene, a single layer of carbon atoms, could be used for a variety of medical purposes.--Courtesy of Graphene Flagship

Another advantage of noncovalent wrappings is their "functionalization." That means that other molecules for tasks like drug delivery can be added to the polymer coating, and if the coating is of high enough quality, it will remain intact even if the functional molecules are removed from its surface, the paper explains.

Researchers have proposed functionalizing the nanotube coating through the incorporation of antibodies. The cargo could also include chemotherapy drugs, small interfering RNAs (used in the RNAi delivery paradigm) and peptides, according to the review.

If all the R&D dollars being spent on graphene live up to the hype and produce a decent return on investment, in a fistful of years, graphene sensors and diagnostics will someday be central to medicine. Add drug-delivering carbon nanotubes wrapped in polymeric coatings to the list.

- read the release | here's the entire literature review (PDF)