Making graphene oxide hemocompatible

Graphene holds potential for numerous applications including biomedical. The most interesting property of graphene for biomedical use has been its large surface-to-volume ratio and the ability to functionalize the material, for example with pharmaceuticals for intravenous drug delivery.

Graphene itself is hydrophobic, making it unstable in aqueous solutions, hence incompatible with intravenous use. Graphene oxide (GO), on the other hand, is stable in solution and has been the material of choice for graphene-based biomedical applications. Although intravenous use of GO puts it in direct contact with red blood cells (RBCs), the hemocompatibility of GO has just recently become a topic of research. Now a group of researchers from several centers in Spain has performed systematic tests of hemocompatibility of GO, showing that although GO does interact strongly with RBCs, causing hemolysis, hemolysis is decreased when GO is previously coated with lipid membranes.

Image: Tomogram of graphene oxide sheet incubated with lipids

The research paper, recently published in Langmuir, first highlights that GO interacts with lipid membranes, like those that coat the outer side of all cells in living organisms. GO binds to the membranes with an efficacy that can be controlled with the salinity of the solution. It was further shown that GO ruptures vesicles that have a lipid membrane and aqueous contents, which represents a model living cell. The same is demonstrated for interaction with real RBCs. Thus the scientists show that GO reacts with blood cells in such a way as to rupture them. However, when GO is mixed with lipid membranes prior to interaction with RBCs, the damaging action of GO is almost totally suppressed.

The discovery prompts the conclusion that GO can be used in biomedical applications, if it is coated with a protective layer of lipids. This finding is in agreement with previous work that showed a reduction in hemolytic activity of GO when it is coated with chitosan, bovine serum albumin or heparin coatings.