First of all, do not say whether these products contain real graphene, and do not say that there is no data to support the various magical effects advertised by businesses, these can at least more or less reflect the public's expectations of graphene, this magical material.

    In fact, in the field of rigorous scientific research, scholars have been exploring more possible applications of graphene. For example, can you imagine graphene being used to 3D print artificial blood vessels? Recently, Alvaro Mata and other researchers at Queen Mary University of London published a paper in the journal Nature Communications, reporting a disordered protein and graphene oxide (GO) co-assembly system, which can form capillary-like structures in a manner similar to 3D bio-printing. Has some of the physiological properties of blood vessel tissue, and is expected to be used in the lab to mimic key parts of human tissues and organs.

Self-assembly of a vascular-like structure. Photo credit: Nat. Commun.

    GO is rich in oxygen-containing functional groups (hydroxyl, alkoxy, carbonyl and carboxyl) and is often electronegative itself, so it can facilitate interactions with different molecules -especially positively charged ones. The researchers' choice of recombinamers to interact with graphene oxide is a disordered protein -Elastin-like recombinamers (ELRs) -which is a class of recombinamers based on the natural elastin motif Val-Pro-Gly-X-Gly (VPGXG, Where X can beany amino acid other than proline), resulting in elastin-like peptides. Previous studies have shown that these polypeptide molecules take on different molecular conformations with temperature changes, can exhibit reversible phase transitions, and have been used to make biocompatible materials. The three ELRs involved in this paper are shown in Figure a below.

Molecular construction and co-assembly principles. Photo credit: Nat. Commun.

    Interestingly, when the ELK1 solution drops into the GO solution, a multilayer film with a thickness of ~ 50μm can be formed at the interface around the droplet. The film is self-assembled by the charge interaction of ELK1 and GO. Then, as the syringe moves while injecting the ELK1 solution, it can form a tubular structure, whose inner diameter is determined by the size of the injection needle. The system can form capillary-like structures through collaborative self-assembly in a culture medium where cells are present, and the cells can be embedded in and on the wall of the tube.

Self-assembly, structure and properties of ELK1-GO. Photo credit: Nat. Commun.

    If the ELK1 solution is put into the extrusion 3D printer as "ink", you can freely "print" different shapes of tubular structures in the GO solution. As a result, the researchers printed tubes with different inner diameters, different sizes, different torsion angles and different forks, which can withstand a water flow of up to 12.5 mL/min for at least 24 hours. The highest flow rate will produce a shear stress of 0.26 N/m2, which is not far from the average shear stress generated by the common carotid artery (0.7 N/m2).

    Since the reason for the self-assembly comes from the strong interaction between ELK1 and GO at the molecular scale, the solution concentration of both will certainly affect the properties of the resulting tubular structure. The study found that the interaction was strongest when the concentration ratio of the two was between 15 and 40, so during the "printing" process, the concentration of ELK1 was maintained at 2%, while the concentration of GO was selected to be 0.05%, 0.10% and 0.15%. As expected, the strength, fracture strain and toughness of the tubular structure all increased with the increase of GO concentration. The tubular structures prepared with 0.10% GO solution had the highest modulus of elasticity.

Molecular interaction and mechanical properties test of ELK1 and GO. Photo credit: Nat. Commun.

    At different temperatures, the structural properties formed by the co-assembly of ELK1 and GO are also different. It was found that the tubular structure obtained at the transition temperature (Tt) of ELK1 at 30 °C was more stable and clearer than that obtained at 4 °C and 45 °C, indicating a stronger interaction between ELK1 and GO at 30 °C. The 3D conformation of ELK1 at different temperatures plays a key role in its interaction with the GO sheet, which in turn influences the diffusion-reaction mechanism that determines the performance of the resulting ELK1-Go tubular structure.

    Since we wish to apply this system to artificial blood vessels, biological validation is essential. A self-assembled tubular structure in a cell culture medium, cells can spread and grow in the wall and lumen of the tube for more than seven days. This is despite the fact that GO is known to be cytotoxic to endothelial cells in vitro at concentrations above 100 ng/mL. However, the researchers found that the ELK1-GO composite can reduce the cytotoxic level of GO and greatly improve cell survival. In addition, the composite also has good biocompatibility, and these results provide a possibility for the application of ELK1-GO co-assembly system in artificial blood vessels.

The cytotoxicity and biocompatibility of ELK1-GO were verified in vitro. Photo credit: Nat. Commun.

    "People are very interested in developing materials and manufacturing processes that mimic nature. However, the ability to build functional materials and devices through self-assembly of molecules has been limited ", Yuanhao Wu says [1], "This study introduces a new method to combine proteins with graphene oxide through self-assembly, which can be easily combined with manufacturing techniques to build biofluid devices, Enabling researchers to replicate key parts of human tissues and organs in the lab."

References:

1. Biomaterial discovery enables 3D printing of tissue-like vascular structures

https://www.nottingham.ac.uk/news/biomaterial-discovery-enables-3d-printing

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