Graphene Hollow Micropatterns via Capillarity-Driven Assembly for Drug Storage and Neural Cell Alignment.

Electrical conductivity, cell-guided surface topology, and drug storage capacity of biomaterials are attractive properties for the repair and regeneration of anisotropic tissues with electrical sensitivity, such as nerves. However, designing and fabricating implantable biomaterials with all these functions remain challenging. Herein, we developed a freestanding graphene substrate with micropatterned surfaces by a simple templating method. Importantly, the raised surface micropatterns had an internal hollow structure. The morphology results showed that the template microgroove width and the graphene nanosheet size were important indicators of the formation of the hollow structures. Through real-time monitoring and theoretical analysis of the formation process, it was found that the main formation mechanism was the delamination and interlayer movement of the graphene nanosheets triggered by the evaporation-induced capillary force. Finally, we achieved the controlled release of loaded microparticles and promoted the orientation of rat dorsal root ganglion neurons by applying an electric field to the hollow micropatterns. This capillarity-induced self-assembly strategy paves the way for the development of high-performance graphene micropatterned films with a hollow structure that have potential for clinical application in the repair of nerve injury.

In Vivo Disintegration and Bioresorption of a Nacre-Inspired Graphene-Silk Film Caused by the Foreign-Body Reaction.

Graphene-based substrates are emerging as a promising functional platform for biomedical applications. Although dispersible graphene sheets have been demonstrated to be biodegradable, their assembled macroscopic architectures are biopersistent because of strong π-π interactions. In this study, we developed a nacre-inspired graphene-silk nanocomposite film by vacuum filtration with a subsequent green chemical reduction procedure. The "brick-and-mortar" architecture not only ensures the mechanical and electrical properties of the film but also endows it with disintegrable and bioresorbable properties following rat subcutaneous implantation. Furthermore, covalent cross-linking leads to the formation of graphene with decreased interlayer spacing, which effectively prolongs the residence time in vivo. We found that enzymatic treatment created microcracks on the film surface and that the foreign-body reaction was involved in the deformation, delamination, disintegration, and phagocytosis processes of the nanocomposite films. This bioinspired strategy paves the way for the development of high-performance graphene-based macroscopic biomaterials with tunable bioresorbability.