How to enhance the functionality of microencapsulated cells by using graphene oxide nanoparticles

Introduction: Cell microencapsulation consists on the immobilization of cells within an alginate matrix surrounded by a semi-permeable membrane that allows the release of therapeutic drugs. This technology represents an... [ view full abstract ]

Introduction: Cell microencapsulation consists on the immobilization of cells within an alginate matrix surrounded by a semi-permeable membrane that allows the release of therapeutic drugs. This technology represents an opportunity to develop long-term de novo synthesized drug delivery systems for the treatment of chronic diseases. However, several challenges need to be overcome before it can be translated into the clinic. For instance, a higher viability of the cells would be highly desirable. Graphene oxide (GO) has shown to promote the adhesion and proliferation of several cell types. Thus, we fabricated hybrid alginate-GO capsules in order to improve the viability of erythropoietin (EPO) secreting C2C12 myoblasts.
Methods: Myoblasts were encapsulated into alginate or hybrid alginate-GO microcapsules. First, we studied the main physical parameters of the microcapsules. Next, early apoptosis and viability of the cells was quantified by flow cytometry. Also, the CCK8 assay was performed to analyze the metabolic activity and the cell membrane integrity was determined. Finally, EPO production was detected by Elisa. For in vivo studies, syngeneic C3H mice were implanted and blood samples were collected weekly for hematocrit determination.
Results and Discussion: We were able to produce microcapsules with GO in their core and proved that their physical characteristics were not substantially modified. Also, we determined that 25-50 µg/ml of GO is the most suitable concentration for enhancing the viability of encapsulated cells, since this rank provided lower cell death and better metabolic activity. However, even at the lowest GO concentration, the quantity of EPO detected on the medium was low, most likely due to its adsorption to the GO surface. Therefore, we tested if a protein pre-coating could attenuate the capacity of GO to adhere the therapeutic protein. Interestingly, serum-coating effectively avoided the adsorption of EPO to the nanoparticles and enhanced, even more, the viability, membrane integrity and drug release of encapsulated cells. Finally, myoblasts encapsulated in hybrid alginate-protein coated GO microcapsules showed to be functional in vivo as they increased hematocrit levels on mice. Therefore, these results provide another step for the future pre-clinical application of GO nanoparticles in combination with cell microencapsulation.