*Article* **Aminated Graphene-Graft-Oligo(Glutamic Acid) /Poly(**ε**-Caprolactone) Composites: Preparation, Characterization and Biological Evaluation**

**Mariia Stepanova <sup>1</sup> , Olga Solomakha <sup>1</sup> , Maxim Rabchinskii 2,\*, Ilia Averianov <sup>1</sup> , Iosif Gofman <sup>1</sup> , Yuliya Nashchekina <sup>3</sup> , Grigorii Antonov <sup>2</sup> , Aleksey Smirnov <sup>2</sup> , Boris Ber <sup>2</sup> , Aleksey Nashchekin <sup>2</sup> and Evgenia Korzhikova-Vlakh 1,\***


**Citation:** Stepanova, M.; Solomakha, O.; Rabchinskii, M.; Averianov, I.; Gofman, I.; Nashchekina, Y.; Antonov, G.; Smirnov, A.; Ber, B.; Nashchekin, A.; et al. Aminated Graphene-Graft-Oligo(Glutamic Acid) /Poly(ε-Caprolactone) Composites: Preparation, Characterization and Biological Evaluation. *Polymers* **2021**, *13*, 2628. https://doi.org/10.3390/ polym13162628

Academic Editor: Ilaria Armentano

Received: 15 July 2021 Accepted: 4 August 2021 Published: 7 August 2021

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**Abstract:** Biodegradable and biocompatible composites are of great interest as biomedical materials for various regeneration processes such as the regeneration of bones, cartilage and soft tissues. Modification of the filler surface can improve its compatibility with the polymer matrix, and, as a result, the characteristics and properties of composite materials. This work is devoted to the synthesis and modification of aminated graphene with oligomers of glutamic acid and their use for the preparation of composite materials based on poly(ε-caprolactone). Ring-opening polymerization of N-carboxyanhydride of glutamic acid γ-benzyl ester was used to graft oligomers of glutamic acid from the surface of aminated graphene. The success of the modification was confirmed by Fouriertransform infrared and X-ray photoelectron spectroscopy as well as thermogravimetric analysis. In addition, the dispersions of neat and modified aminated graphene were analyzed by dynamic and electrophoretic light scattering to monitor changes in the characteristics due to modification. The poly(ε-caprolactone) films filled with neat and modified aminated graphene were manufactured and carefully characterized for their mechanical and biological properties. Grafting of glutamic acid oligomers from the surface of aminated graphene improved the distribution of the filler in the polymer matrix that, in turn, positively affected the mechanical properties of composite materials in comparison to ones containing the unmodified filler. Moreover, the modification improved the biocompatibility of the filler with human MG-63 osteoblast-like cells.

**Keywords:** aminated graphene; graphene modification; grafting from; oligomers of glutamic acid; poly-ε-caprolactone; biocompatible polymer composites
