Biocompatible multilayer capsules engineered with a graphene oxide derivative: synthesis, characterization and cellular uptake.

Graphene-based capsules have strong potential for a number of applications, including drug/gene delivery, tissue engineering, sensors, catalysis and reactors. The ability to integrate graphene into carrier systems with three-dimensional (3D) geometry may open new perspectives both for fundamental tests of graphene mechanics and for novel (bio)technological applications. However, the assembly of 3D complexes from graphene or its derivatives is challenging because of its poor stability under biological conditions. In this work, we attempted to integrate a layer of graphene oxide derivative into the shell of biodegradable capsules by exploiting a facile layer-by-layer (LbL) protocol. As a first step we optimized the LbL protocol to obtain colloidal suspensions of isolated capsules embedding the graphene oxide derivative. As a following step, we investigated in detail the morphological properties of the hybrid capsules, and how the graphene oxide derivative layer influences the porosity and the robustness of the multilayer composite shells. Finally, we verified the uptake of the capsules modified with the GO derivative by two cell lines and studied their intracellular localization and biocompatibility. As compared to pristine capsules, the graphene-modified capsules possess reduced porosity, reduced shell thickness and a higher stability against osmotic pressure. They show remarkable biocompatibility towards the tested cells and long-term colloidal stability and dispersion. By combining the excellent mechanical properties of a graphene oxide derivative with the high versatility of the LbL method, robust and flexible biocompatible polymeric capsules with novel characteristics have been fabricated.