Illustration and application of enhancing effect of arginine on interactions between nano-clays: self-healing hydrogels.

Nano-clays (NCs) as a representative type of nano-materials are a source of inspiration for design of new biomedical materials with excellent performances. Research has shown that guanidinium ions (Gu+) can form non-covalent salt-bridge interactions with NCs, serving as "molecular glue" in the fabrication of NC-based composites. However, synthesis of the Gu+-containing molecules is always not easy. Since the natural amino acid arginine (Arg) possesses Gu+, Arg could potentially be a replacement for the synthetic molecules. To prove this possibility, nano-composites were constructed by combining model anisotropic NCs with Arg-modified nano-hydroxyapatite (nHAP-Arg) and polyarginine (poly-Arg), respectively. Formation of molecular interactions between NCs and nHAP-Arg/poly-Arg was demonstrated by enhanced gelation behaviour of NCs. Through taking the unique advantage of Arg, this study can be readily implemented in constructing a variety of NC-based composites with diverse functionalities that are necessary for potential applications in tissue engineering and regenerative medicine.